As the world's tectonic plates crash, grind and dive into one another, they release their pent-up energy in giant earthquakes that can rock the ground, trigger volcanic eruptions, move mountains and unleash tsunamis.

And since scientists figured out how to measure earthquake magnitude in the early 1900s, some truly massive quakes have shaken our planet. These are the monstrous "megathrust" earthquakes, the most powerful quakes in the world. A huge fraction of these earthquakes occurred in a handful of subduction zones along the seismically restless "Ring of Fire" in the Pacific, where tectonic plates dive beneath one another.

From the devastating Sumatran quake and tsunami of 2004 to a monstrous temblor in Siberia that, thankfully, killed no one, here are the 20 largest earthquakes ever recorded, according to the U.S. Geological Survey (USGS).

21. Sanriku-Oki, Japan; 1933; magnitude 8.4

A magnitude 8.4 quake struck near the Sanriku region of Japan on March 2, 1933, according to the USGS. The quake occurred about 180 miles (290 kilometers) offshore of Honshu, Japan.

Most of the deaths resulted from the tsunami the quake generated, which swept away 3,000 homes and destroyed 2,000 others and generated nearly 100-foot (29 meters) waves in Honshu, Japan.

Several decades later, a magnitude 9.0 temblor would rock the same general region, causing the Tōhoku earthquake and tsunami of 2011.

This area is part of the Pacific Ring of Fire, a nearly 25,000-mile-long (40,000 km) horseshoe-shaped belt that is known for both earthquakes and volcanic activity. The ring fringes the boundaries of the Pacific Plate wherever it smashes into its neighboring plates; in the region around Tōhoku, the Pacific Plate is colliding with the North American Plate.

20. Arequipa, Peru; 2001; magnitude 8.4

A magnitude 8.4 earthquake struck 4 miles (6 km) from the coastal town of Atico, Peru, on June 23, 2001. At least 74 people were killed; more than a third of them were swept away by the resulting tsunami. More than 2,600 people were injured, and over 50,000 homes were damaged by the strong ground shaking.

The quake occurred at the boundary of the Nazca and South American plates, where the Nazca Plate is moving northeast at about 3 inches (78 millimeters) per year, smashing into and diving beneath the South American Plate, according to the USGS. Ground shaking as a result of the seismic activity was felt as far away as La Paz, Bolivia.

19. South of Sumatra, 2007, magnitude 8.4

On April 12, 2007, a magnitude 8.4 earthquake struck approximately 76 miles (122 km) offshore of Bengkulu, Indonesia, on the island of Sumatra. The giant quake occurred due to thrust faulting on the boundary between the Sunda and Australian plates.

Around 25 people died, and more than 161 were injured. More than 20,000 buildings were damaged in the cities of Bengkulu and Sumatera Barat, according to the USGS.

The quake marked the fourth magnitude 7.9 or greater temblor to strike the general region that decade; the area was still actively remodeling itself after the monster quake that struck just after Christmas Day in 2004 (see #3).

18. Near Kamchatka Peninsula, 1923, magnitude 8.4

Relatively little is known about the magnitude 8.4 quake that struck off the east coast of Kamchatka, Russia, on Feb. 3, 1923. The sparsely populated area of the Russian Far East sits near the Kuril-Kamchatka Trench, where the Pacific Plate is diving beneath the Okhotsk Plate, a teensy plate that was once thought to be part of the North American Plate.

No reported injuries or deaths occurred, but the quake triggered a modest tsunami, according to the USGS.

17. Kuril Islands, Russia; 1963; magnitude 8.5

Relatively little is known about the quakes that struck the remote Kuril Islands on Oct. 13, 1963. This volcanic archipelago stretches between Russia's Kamchatka Peninsula and Hokkaido, Japan.

No deaths, damage or injuries were reported as a result of this temblor, but it triggered a tsunami that reached the northern Pacific Ocean.

16. Atacama, Chile; 1922; magnitude 8.5

On Nov. 11, 1922, a massive magnitude 8.5 quake struck the Atacama Desert on the border of Argentina and Chile. Even though the epicenter of the earthquake was beneath land, the shaking was so strong that it triggered a tsunami that killed hundreds of people, according to news reports at the time.

15. Banda Sea, Indonesia; 1938; magnitude 8.5

On Feb. 1, 1938, a magnitude 8.5 quake rocked the seafloor about 88 miles (141 km) northwest of Tual, Indonesia. Despite the strength of this temblor, the damage was fairly minor.

Residents of the Banda and Kai islands felt the tremors, while in the city of Tual, glassware broke and a pendulum stopped.

14. Unimak Island, Alaska; 1946; magnitude 8.6

A magnitude 8.6 quake struck Unimak Island on April 1, 1946. Despite its large size, the quake did not destroy any buildings. However, it triggered a 115-foot-high (35 m) tsunami that swept away a lighthouse, along with its five occupants, according to the USGS.

When the tsunami reached Hilo, on the Big Island of Hawaii, it swept away 159 people and caused $26 million in property damage.

Unimak Island is one of the Aleutian Islands, which sit on the restive Ring of Fire, just like many of the other regions struck by large quakes on this list.

13. Andreanof Islands, Alaska; 1957; magnitude 8.6

The quake that struck off of the Andreanof Islands, part of the Aleutian Islands, on March 9, 1957, registered a magnitude 8.6. The quake occurred about 53 miles (86 km) southeast of Adak, Alaska, a tiny village of a few hundred people and the state's southernmost town.

No one was killed, but the quake destroyed two bridges, created a meters-long crack in one road in Adak and damaged houses.

The quake also generated a 49-foot-high (15 m) tsunami that slammed into the nearby Scotch Cap lighthouse, as well as a 26-foot-high (8 m) tsunami that washed away oil lines in Sand Bay. The tsunami then traveled to Hawaii, where it destroyed two villages, and to San Diego, where it also damaged some property.

12. Northern Sumatra, Indonesia; 2005; magnitude 8.6

The area around Sumatra is a seismically active one, with the Indonesian island sitting astride the volcanically active Pacific Ring of Fire.

That seismically unsettled region, where the Australian Plate and Sunda Plate meet, unleashed a massive amount of energy on March 28, 2005, when a magnitude 8.6 quake struck 48 miles (78 km) west of Singkil, at a depth of 18 miles (30 km). More than 1,300 people were killed, another 340 were injured and hundreds of buildings were destroyed, mostly on the island of Nias. The quake was felt as far away as India and Sri Lanka.

The earthquake occurred because the Australian Plate is moving to the northeast at a rate of 2 inches (50 millimeters) per year and is diving into the mantle at the Sunda Trench. According to the USGS, the massive quake was unleashed in the aftermath of the massive Indian Ocean earthquake of 2004 as the faults in the region continued to adjust to that seismic shift.

11. Off the west coast of northern Sumatra, 2012, magnitude 8.6

On April 11, 2012, a magnitude 8.6 temblor struck off the coast of northern Sumatra. Because it struck a few hundred miles off the coast, it was felt as strong shaking in only a few population centers, such as Banda Aceh and Meulaboh, Indonesia. It caused only light structural damage in those metropolitan regions, according to the USGS. Light shaking could be felt as far away as Mumbai, India, and Broome, Australia.

Two people were killed directly by the quake, eight died of heart attacks and 12 were injured.

10. Assam-Tibet, 1950, magnitude 8.6

At least 1,500 people died across eastern Tibet and Assam, India, when this temblor shook the region on Aug. 15, 1950. Ground cracks, large landslides and sand volcanoes struck the area. The quake was felt in China's Sichuan and Yunnan provinces, and as far away as Kolkata, India.

The quake caused large landslides that blocked rivers. When the rivers finally burst through the walls of debris, waves inundated several villages and killed hundreds of people.

This quake is commonly called the Assam-Tibet earthquake or the Assam earthquake, even though the epicenter was in Tibet. The quake struck at the intersection of the most vigorous collision of continental plates on the planet, where the Indian Plate smashes into the Eurasian Plate and dives beneath it. The slow-motion crash helped create the massive Himalayas.

9. Rat Islands, Alaska; 1965; magnitude 8.7

Alaska had been a state for only six years when this huge earthquake triggered a tsunami over 30 feet (10 m) high on Feb. 4, 1965. Despite its size, the quake caused little damage due to its remote location at the tip of the Aleutian Islands. The tsunami was reported in Hawaii and spread as far as Japan.

The temblor was the result of the Pacific Plate diving beneath the North American Plate at the Alaska-Aleutian megathrust, which has been the location of many megathrust earthquakes.

The quake cracked wood buildings and split an asphalt runway. Hairline cracks also formed in the runways at the U.S. Coast Guard's Loran Station.

8. Kamchatka Peninsula, Russia; 2025; magnitude 8.8

On July 29, 2025, a magnitude 8.8 earthquake struck approximately 40 miles (60 km) from Russia's Kamchatka Peninsula, at a depth of 12.8 miles (20.7 km). The earthquake generated multiple tsunamis, with warnings issued in regions across the Pacific, including North America, South America, Japan, Russia and Pacific island nations.

The earthquake occurred when the Pacific plate rubbed against the North American plate. According to the USGS, the likely cause was a slip over a large fault area. It was the largest earthquake since 2011's magnitude 9 Tohoku earthquake in Japan.

7. Off the coast of Ecuador, 1906, magnitude 8.8

On Jan. 31, 1906, a catastrophic magnitude 8.8 earthquake hit off the coast of Ecuador and Colombia and generated a strong tsunami that killed 500 to 1,500 people. The tsunami spread along the coast of Central America, and even lapped at the shorelines in San Francisco and Japan.

The earthquake occurred along the boundary between the Nazca Plate and the South American Plate. Because it hit more than 100 years ago, reports are spotty. But according to the USGS, witnesses reported a huge rush of water in Honolulu Bay. All the steam and sailboats in the bay were turned around, and then a sudden flood tide roared inland.

6. Offshore Maule, Chile; 2010; magnitude 8.8

On Feb. 27, 2010, an earthquake and tsunami hit central Chile. At least 500 people were killed and 800,000 were displaced by the natural disaster. More than 1.8 million people were affected, and the total economic loss was estimated at $30 billion.

Like many other quakes on this list, this temblor took place along the seismically active boundary between the Nazca and South American tectonic plates, which can release bone-shatteringly strong shaking.

The quake hit just over a month after the disastrous magnitude 7.0 quake in Port-Au-Prince, Haiti, which killed more than 200,000 people.

5. Kamchatka Peninsula, Russia; 1952; magnitude 9.0

The world's first recorded magnitude 9.0 earthquake struck off the east coast of Kamchatka on Nov. 4, 1952. The quake generated a 43-foot (13 m) tsunami locally. The tsunami rocked Crescent City, California.

No one died, but in Hawaii, property damage was estimated at up to $1 million ($11.12 million in today's dollars). The waves tossed boats onto the beach, caused houses to collide, destroyed piers, scoured beaches and moved road pavement.

4. Tōhoku, Japan; 2011; magnitude 9.1

On March 11, 2011, a magnitude 9.1 quake triggered a tsunami that left more than 15,700 people dead, more than 4,600 missing, over 5,300 injured and more than 130,900 displaced, according to the USGS. More than 332,000 buildings, 2,100 roads, 56 bridges and 26 railways were damaged as a result of the quake. The quake also damaged nuclear reactors at the Fukushima Daiichi Nuclear Power Plant, leading to one of the biggest nuclear disasters in history. This earthquake was the largest ever recorded in Japan, and cost an estimated $309 billion in damage.

For weeks afterward, strong aftershocks above magnitude 6.0, and even 7.0, continued to rock the region, and the quake sent tsunami waves as far as Hawaii, California and the Galapagos Islands. Even in distant Antarctica, the quakes cracked large slabs of ice from the Sulzberger Ice Shelf, according to the USGS.

The quake was caused by thrust faulting near the Japan Trench, the boundary between the Pacific and North American plates.

3. Sumatra-Andaman Islands, 2004, magnitude 9.1

This quake was the third-largest earthquake in history and the largest since the 1964 earthquake in Prince William Sound, Alaska (see #2). In total, nearly 300,000 people were killed or presumed dead, and about 1.2 million people were displaced by the earthquake and subsequent tsunami in 10 countries in Southeast Asia and East Africa.

Extremely strong shaking was felt in Banda Aceh, but the deadliest aspect of this quake was the resulting tsunami, which caused more deaths than any other in recorded history up to that point. The tsunami was recorded nearly worldwide on tide gauges in the Indian, Pacific and Atlantic oceans.

The massive quake struck one day after Christmas along the interface of the Indian and Burma tectonic plates and was caused by the release of stress that developed as the Indian Plate dived beneath the Burma microplate. The massive fault zone, which was offshore, was as long as California, according to the USGS.

2. Prince William Sound, Alaska; 1964; magnitude 9.2

This great earthquake and ensuing tsunami took 128 lives and caused about $311 million in property loss. The earthquake damage was heavy in many towns, including Anchorage, which was about 75 miles (120 km) northwest of the epicenter. The quake, which struck on March 27, 1964, ruptured along a seismically active fault between the North American and Pacific plates. The shaking lasted about 3 minutes.

Landslides in Anchorage caused heavy damage. Huge slides occurred in the downtown business section, and water mains and gas, sewer, telephone and electrical systems were disrupted throughout the area.

1. Valdivia, Chile; 1960; magnitude 9.5

Approximately 1,655 people died in the largest earthquake ever recorded, which struck Valdivia, Chile, on May 22, 1960. Thousands more were injured, and millions were left homeless. Southern Chile suffered $550 million in damage.

The quake triggered a tsunami that killed 61 people in Hawaii, 138 in Japan and 32 in the Philippines.

The earthquake struck where the Nazca Plate dives underneath the South American Plate, on the Peru-Chile Trench.

Editor's Note: This article was originally published on 2012.

The Japan earthquake and tsunami of 2011, also known as the 2011 Tohoku earthquake and tsunami or the Great Tohoku earthquake, was a natural disaster that shook northeastern Japan on March 11, 2011. The disaster began when a magnitude-9 earthquake shook the region in the early afternoon, unleashing a savage tsunami.

The effects of the great earthquake, which was the strongest in Japan's recorded history, were felt around the world, from Norway's fjords to Antarctica's ice sheet. Tsunami debris has continued to wash up on North American beaches years later.

In Japan, residents are still recovering from the disaster. As of November 2021, there were still about 39,000 evacuees who lost their homes; 1,000 of them were still living in temporary housing, according to Japan's Reconstruction Agency.

More than 120,000 buildings were destroyed, 278,000 were half-destroyed and 726,000 were partially destroyed, according to the agency. The direct financial damage from the disaster is estimated to be about $199 billion dollars (about 16.9 trillion yen), according to the Japanese government. The total economic cost could reach up to $235 billion, the World Bank estimated, making it the costliest natural disaster in world history.

Related: How Japan's 2011 Earthquake Happened

A surprise disaster

The unexpected disaster was neither the largest nor the deadliest earthquake and tsunami to strike this century. That record goes to the 2004 Banda Aceh earthquake and tsunami in Sumatra, a magnitude-9.1, which killed more than 230,000 people. But Japan's one-two punch proved especially devastating for the earthquake-savvy country, because few scientists had predicted the country would experience such a large earthquake and tsunami.

Japan's scientists had forecast a smaller earthquake would strike the northern region of Honshu, the country's main island. Nor did they expect such a large tsunami. But there had been hints of the disaster to come. The areas flooded in 2011 closely matched those of a tsunami that hit Sendai in A.D. 869. In the decade before the 2011 Tohoku earthquake, a handful of Japanese geologists had begun to recognize that a large earthquake and tsunami had struck the northern Honshu region in that year. However, their warnings went unheeded by officials responsible for the country's earthquake hazard assessments, Live Science previously reported. Now, tsunami experts from around the world have been asked to assess the history of past tsunamis in Japan, to better predict the country's future earthquake risk.

"For big earthquakes, the tsunami is going to be the big destructive factor," said Vasily Titov, director of the National Oceanic and Atmospheric Administration's Center for Tsunami Research in Seattle, Washington told Live Science. "But if the nation is prepared, warning and education definitely saves lives. Compare the human lives lost in Sumatra and Japan. It's about 10 times less."

The 2011 Tohoku earthquake

The 2011 Tohoku earthquake struck offshore of Japan, along a subduction zone where two of Earth's tectonic plates collide. In a subduction zone, one plate slides beneath another into the mantle, the hotter layer beneath the crust. The great plates are rough and stick together, building up energy that is released as earthquakes. East of Japan, the Pacific plate dives beneath the overriding Eurasian plate. The temblor completely released centuries of built up stress between the two tectonic plates, a recent study found.

The March 11 earthquake started on a Friday at 2:46 p.m. local time (5:46 a.m. UTC). It was centered on the seafloor 45 miles (72 kilometers) east of Tohoku, at a depth of 15 miles (24 km) below the surface. The shaking lasted about six minutes. 

Scientists drilled into the subduction zone soon after the earthquake and discovered a thin, slippery clay layer lining the fault, according to a 2013 study in the journal Science. The researchers think that this clay layer allowed the two plates to slide an incredible distance, some 164 feet (50 meters), facilitating the enormous earthquake and tsunami. 

Early warning

Residents of Tokyo received a minute of warning before the strong shaking hit the city, thanks to Japan's earthquake early warning system. The country's stringent seismic building codes and early warning system prevented many deaths from the earthquake, by stopping high-speed trains and factory assembly lines. People in Japan also received texted alerts of the earthquake and tsunami warnings on their cellphones.

Death toll of the 2011 earthquake and tsunami

The number of confirmed deaths is 19,747 as of December, 2021, according to the reconstruction agency. More than 2,500 people are still reported missing.

Less than an hour after the earthquake, the first of many tsunami waves hit Japan's coastline. The tsunami waves reached run-up heights (how far the wave surges inland above sea level) of up to 128 feet (39 meters) at Miyako city and traveled inland as far as 6 miles (10 km) in Sendai. The tsunami flooded an estimated area of approximately 217 square miles (561 square kilometers) in Japan, according to the National Oceanic and Atmospheric Administration .

The waves overtopped and destroyed protective tsunami seawalls at several locations. The massive surge destroyed three-story buildings where people had gathered for safety. Near Oarai, the tsunami generated a huge whirlpool offshore, captured on video.

The Fukushima nuclear meltdown

The tsunami caused a cooling system failure at the Fukushima Daiichi Nuclear Power Plant, which resulted in a level-7 nuclear meltdown and release of radioactive materials. The electrical power and backup generators were overwhelmed by the tsunami, and the plant lost its cooling capabilities.  

"Fukushima was created by the tsunami. The earthquake was not a factor," Titov said. "Fukushima was designed for a tsunami smaller than the one we saw."

Very low levels of radioactive chemicals that leaked from Fukushima have been detected along the North American coast offshore Canada and California. Trace amounts of cesium-134 and cesium-137 (radioactive isotopes) were found in seawater collected in 2014 and 2015, Live Science reported at the time.

The response

In the tsunami's aftermath, Japan's Meteorological Agency was criticized for issuing an initial tsunami warning that underestimated the size of the wave. In some regions, such as Miyagi and Fukushima, only 58% of people headed for higher ground immediately after the earthquake, according to a Japanese government study published in August 2011. Many people also underestimated their personal risk, or assumed the tsunami would be as small as ones they had previously experienced, the study found.

Scientists from around the world descended on Japan following the earthquake and tsunami. Researchers sailed offshore and dropped sensors along the fault line to measure the forces that caused the earthquake. Teams studied the tsunami deposits to better understand ancient sediment records of the deadly waves. Earthquake engineers examined the damage, looking for ways to build buildings more resistant to quakes and tsunamis. 

"The tsunami itself died out a long time ago, but the effects in Japan will be there for decades," Titov told Live Science.

Worldwide effects

The tsunami waves also traveled across the Pacific, reaching Alaska, Hawaii and Chile. In Chile, some 11,000 miles (17,000 km) distant, the tsunami was 6.6 feet (2 meters) high when they reached the shore, according to the Pacific Tsunami Warning Center. 

Related: Weird Earth Movement After Japan Earthquake Finally Explained

The surge of water carried an estimated 5 million tons of debris out to sea, the National Oceanic and Atmospheric Agency reported. Japanese docks and ships, and countless household items, have arrived on U.S. and Canadian shores in the ensuing years. The U.S. Coast Guard fired on and sank the derelict boat 164-foot Ryou-Un Maru in 2012 in the Gulf of Alaska. The ship started its journey in Hokkaido. 

Amazing facts

Here are some of the amazing facts about the Japan earthquake and tsunami.

• The earthquake shifted Earth on its axis of rotation by redistributing mass, like putting a dent in a spinning top. The temblor also shortened the length of a day by about a microsecond.
• More than 5,000 aftershocks hit Japan in the year after the earthquake, the largest a magnitude 7.9.
• About 250 miles (400 km) of Japan's northern Honshu coastline dropped by 2 feet (0.6 meters), according to the U.S. Geological Survey.
• The jolt moved Japan's main island of Honshu eastward by 8 feet (2.4 m).
• The Pacific Plate slid westward near the epicenter by 79 feet (24 m).
• In Antarctica, the seismic waves from the earthquake sped up the Whillans Ice Stream, jolting it by about 1.5 feet (0.5 m).
• The tsunami broke icebergs off the Sulzberger Ice Shelf in Antarctica.
• As the tsunami crossed the Pacific Ocean, a 5-foot high (1.5 m) high wave killed more than 110,000 nesting seabirds at the Midway Atoll National Wildlife Refuge.
• In Norway, water in fjords pointing toward Japan sloshed back and forth as seismic waves from the earthquake raced through.
• The earthquake produced a low-frequency rumble called infrasound, which traveled into space and was detected by the Goce satellite.
• Buildings destroyed by the tsunami released thousands of tons of ozone-destroying chemicals and greenhouse gases into the air.

Additional resources

• How to Build an Emergency Survival Kit
• Red Cross Tsunami Survival Guide
• Ready.gov – What To Do During An Earthquake

Bibliography

Vasily Titov, Chief Scientist of the National Oceanic and Atmospheric Administration's (NOAA) Center for Tsunami Research in Seattle, Washington.

“Status of Reconstruction and Reconstruction Efforts.” Japan Reconstruction Agency, Dec. 2021. https://www.reconstruction.go.jp/english/

P.M. Fulton et al. “Low Coseismic Friction on the Tohoku-Oki Fault Determined from Temperature Measurements,” Science, Vol 342, Dec. 2013. https://www.science.org/doi/10.1126/science.1243641

NOAA/ National Weather Service U.S. Tsunami Warning System. https://www.tsunami.gov/

Japan Tsunami Marine Debris. NOAA Marine Debris Program. https://marinedebris.noaa.gov/disaster-debris/japan-tsunami-marine-debris

This article was updated Feb. 11, 2022 by Live Science Senior Writer Brandon Specktor.

WASHINGTON — Tsunamis, the giant waves generated by earthquakes under the sea, are known for flooding vulnerable coastal areas with vast quantities of water. But a tsunami that struck Japan in 1993 brought a different kind of destruction — it set the harbor on fire.

Following a magnitude-7.8 earthquake in the Sea of Japan on July 12 of that year, a tsunami wave barreled toward Okushiri Island in northern Japan. Suddenly, several boats in the port spontaneously burst into flames, and winds from the tsunami drove the blaze inland, to devastating effect, according to Yuji Enomoto, a professor emeritus at Shinshu University in Japan.

This astonishing phenomenon was documented at the time by video crews with NHK, Japan's biggest broadcasting company, but the footage has long been inaccessible, Enomoto told Live Science. [Waves of Destruction: History's Biggest Tsunamis]

Even so, Enomoto recently gained access to the elusive footage. He used the video — along with laboratory experiments — to interpret what caused the dangerous "tsunami fires," and he presented an explanation of the strange event on Dec. 13 here at the annual meeting of the American Geophysical Union (AGU).

"Utter Devastation"

The 1993 Hokkaido earthquake was the strongest to strike Japan in 25 years, producing "scenes of utter devastation, with houses and Buddhist temples splintered in the mud, boats thrown far inland, and roofs of some homes floating out to sea," The New York Times reported on July 14 of that year.

In the aftermath, rescue workers confirmed that 97 people were killed, as many as 190 were injured, and more than 160 people were missing, according to The Times.

Low-lying Okushiri Island bore the brunt of the tsunami. About 10 minutes after the earthquake, the first tsunami wave struck Aonae Harbor on the island's western coast, Enomoto and his colleagues reported. Without warning, five fishing boats spontaneously caught fire almost simultaneously. As the second tsunami wave hurtled toward shore, it generated powerful winds that pushed the burning boats to the coastal area, spreading the fire into the city.

What caused those fires? Methane gases buried in the seafloor and stirred up by the tsunami were likely to blame, according to the researchers.

"White and bubbling"

Witness accounts from the island in the minutes before the fires flared up described mists rising and seawater "foaming," Enomoto explained.

"The offshore area looked shining white and bubbling," one witness said.

Those bubbles might have been the result of released methane, which can be combustible under certain conditions. While there are no photographs or video that show the ocean bubbling, a similar scene was captured following the 2011 earthquake off the Pacific coast of Tōhoku — a magnitude 9.0 to 9.1 — in video taken by the Japan Ground Self-Defense Force. And a similar fire emerged afterward, the researchers wrote. [Biggest Earthquakes in History]

While NHK captured footage of the 1993 fires, their video also included disturbing scenes of people swept away by the giant waves, and network officials prohibited its broadcast after the tragedy. However, Enomoto was able to view the footage — confirming eyewitness reports of the fires — and received permission from NHK to use several stills for the purpose of his research, he said.

According to Enomoto, the bubbles that people described seeing in 1993 — and which appeared again in 2011 — represented methane that was formerly embedded in the seafloor but was dislodged by the ground sliding; the methane bubbles were squeezed up and out into the air by the tsunami front, which transported them to the shore area.

"Bacterial mats suggesting methane release have been found off the west of Okushiri Island, where the tsunami originated," the researchers reported.

To test whether the released methane could have caused the fires, Enomoto and his colleagues conducted experiments with seawater that held methane, to see if certain conditions could generate an electrostatic charge. They found that when electrostatic energy generated a charge of 0.28 millijoules, the methane would catch fire. If the charged air during a tsunami reached at least that level of electrostatic energy, it would be enough to ignite the methane bubbles, Enomoto explained.

The researchers concluded that methane electrostatically ignited in 1993 when the wind violently drove released methane into Aonae Harbor's quay wall. Methane bubbles that had accumulated on the decks of the fishing boats sparked as well, and the fire spread further when it reached oil or gasoline leaking from a car that had been swept into the harbor.

These so-called tsunami fires are an underestimated and understudied hazard of tsunamis, Enomoto told Live Science. As there are significant quantities of methane buried in coastal regions off Japan, this merits closer attention in order to head off fires that could potentially be triggered by powerful earthquakes, he added.

• In Pictures: Japan Earthquake & Tsunami
• Image Gallery: This Millennium's Destructive Earthquakes
• Photos: The Devastating Damage from Indonesia Earthquake & Tsunami

Original article on Live Science.

The devastating 2011 tsunami in Japan dragged several thousand tons of debris out to sea. Empty ships, splintered docks, wooden beams from homes, TV sets, refrigerators, buoys, buckets and plastic bottles crossed the Pacific Ocean in the months and years following the disaster. 

The wreckage was a ghostly sight as it washed up on beaches from Hawaii to Alaska. But a new study claims the tsunami debris was actually teeming with life.

Scientists counted nearly 300 species from Japan that hitched rides across the ocean aboard debris. [In Pictures: Japan Earthquake & Tsunami]

The researchers, who reported the discovery in the journal Science yesterday (Sept. 28), say it's the first time in recorded history that diverse communities of coastal species have rafted across an ocean.

"I didn't think that most of these coastal organisms could survive at sea for long periods of time," study co-author Greg Ruiz, a marine biologist at the Smithsonian Environmental Research Center in Maryland, said in a statement. The open ocean is thought to be a harsh environment for creatures that normally cling to the coasts.

But from spring 2012 to spring 2017, Ruiz and his colleagues counted at least 289 invertebrate and fish species arriving from Japan attached to debris, still alive. The creatures ranged from mussels and barnacles to sea stars, worms and jellyfish relatives. None had been previously known to raft across oceans, but Ruiz explained that these species just didn't have the opportunity to make the journey in the past.

"Now, plastic can combine with tsunami and storm events to create that opportunity on a large scale," Ruiz said.

Indeed, the nonbiodegradable items like plastics, fiberglass and styrofoam continue to wash ashore; meanwhile, incidents of wooden wreckage coming ashore declined dramatically after 2014, according to the study.

"Given that more than 10 million tons of plastic waste from nearly 200 countries can enter the ocean every year —an amount predicted to increase by an order of magnitude by 2025 —and given that hurricanes and typhoons that could sweep large amounts of debris into the oceans are predicted to increase due to global climate change, there is huge potential for the amount of marine debris in the oceans to increase significantly," lead study author James Carlton, an invasive species expert with the Maritime Studies Program at Williams College in Massachusetts and Mystic Seaport in Connecticut, said in a statement.

The researchers worry that marine debris could be a vector for invasive species, which can disrupt local ecosystems. It's not clear yet if any of the ocean-crossing species from Japan will start colonies in California, Oregon or the other places where they've landed, but the researchers say the process could take years.

Originally published on Live Science.

A so-called seismic zone off the coast of Alaska could trigger deadly tsunamis like the one that caused the Fukushima nuclear disaster in Japan in 2011, a new study finds.

Identifying other seismic zones — a region high in seismic activity such as tremors and earthquakes — with these features could help researchers identify areas that could produce catastrophic waves, the scientists added.

Tsunamis are monster waves that can grow to be more than 100 feet (30 meters) high. They are typically caused by earthquakes; for example, the 2004 Banda Aceh earthquake and tsunami killed about 250,000 people in Indonesia, and the 2011 Tohoku earthquake and tsunami that struck offshore Japan killed about 20,000 people and triggered the Fukushima nuclear disaster. [Waves of Destruction: History's Biggest Tsunamis]

Major tsunamis often result at the shallow portions of subduction zones, the areas where one of the tectonic plates that make up Earth's surface dives below another. These crash zones are dangerously active, and these tectonic interactions can cause the world's biggest earthquakes and worst tsunamis.

In the past 20 years or so, researchers have discovered that the seismic zones that lead to tsunamis often have three key features. First, the boundary where the tectonic plates meet is often rough instead of smooth. This keeps the plates from easily slipping past each other, allowing energy to build up between the plates. When this built-up energy finally gets released, it can trigger a major earthquake, according to the researchers.

Second, these danger zones may also possess hard rock rather than sediment near the seafloor and on both sides of the plate boundary. This can permit more motion from an earthquake to occur near the seafloor, for more powerful tsunamis, the researchers said.

A third key feature seen with the 2011 Tohoku earthquake is a series of cracks or faults rooted in the plate boundary. These faults may suggest that the plate boundary is especially active in its shallow portions and more prone to generating tsunamis,said study lead author Anne Bécel, a marine geophysicist at Columbia University's Lamont-Doherty Earth Observatory in the Palisades, New York.

Now, scientists find that a segment of the subduction zone off the coast of Alaska also bears this deadly trio of tsunami-linked features. Its geological structure resembles the kind that was to blame for the 2011 Tohoku tsunami, according to the new study.

The researchers imaged the 120-mile-wide (200 kilometers) Shumagin seismic gap in the Alaska Peninsula that stretches southwest from mainland Alaska. The research vessel Marcus G. Langseth used an array of air guns to generate sound waves, and then used two 5-mile-long (8 km) arrays of seismic sensors to detect the sound waves that reflected off geological features of the Shumagin gap.

Bécel and her colleagues found that the structure of the Shumagin seismic gapmay explain the tsunami-generating earthquake that occurred in its area in 1788. Given the way the Shumagin gap is oriented, a major tsunami from it "will reach Hawaii and possibly other islands in the Pacific — for example, the Marquesas and Austral Islands," Bécel told Live Science. The resulting tsunamis would likely not reach cities such as Anchorage, Alaska; Vladivostok, Russia; Seattle; or Vancouver, British Columbia, she added.

Bécel noted that the Shumagin gap has not released a strong earthquake in 150 years. She added that GPS data monitoring of the Shumagin gap's movements suggest that it is not accumulating enough strain to produce a major earthquake on its own.

However, the researchers noted that a seismic zone known as the Semidi segment, which neighbors the Shumagin gap, is accumulating strain and appears to rupture every 50 to 70 years. Bécel noted that if the Semidi segment does give off an earthquake, its energy could travel into the Shumagin gap and generate a large tsunami.

Other seismic zones with similar features may include the Kuril subduction zoneoff the Russian coast and potentially the Unimak segment off the Alaskan coast, Bécel said. Further analysis of such areas may improve researchers' "ability to anticipate regions capable of generating large tsunamis," she added.

The scientists detailed their findings online July 24 in the journal Nature Geoscience.

Original article on Live Science.

A magnitude-6.9 earthquake struck yesterday off the coast of Fukushima, Japan, likely along the same fault that ruptured in 2011, unleashing a massive 9.0-magnitude temblor that triggered deadly tsunamis and caused widespread destruction. Over the course of its history, Japan has seen its share of shaking, but what makes this part of the world so susceptible to big earthquakes?

The answer has to do with Japan's location. The island nation lies along the so-called Pacific Ring of Fire, an imaginary horseshoe-shaped zone that follows the rim of the Pacific Ocean, where many of the world's earthquakes and volcanic eruptions occur. In fact, 81 percent of the world's largest earthquakes happen in this active belt, according to the U.S. Geological Survey (USGS). [Image Gallery: This Millennium's Destructive Earthquakes]

"The Earth's surface is broken up into about a dozen or so major chunks that are all moving around. Where they all interact at their edges, interesting things happen," Douglas Given, a geophysicist with the USGS in Pasadena, California, previously told Live Science.

Within the Pacific Ring of Fire, several tectonic plates mash and collide. In what are known as subduction zones, one plate bends and slides underneath the other, causing the oceanic crust to sink into the Earth's mantle.

"From Alaska down to Japan and the Philippines, all the way down around the western Pacific — and then the boundary of the west coast of South America and central America — are all big subduction zones," said Robert Smith, an emeritus professor of geophysics at the University of Utah.

Japan itself sits atop a complex mosaic of tectonic plates that grind together and trigger deadly earthquakes and volcanic eruptions, Smith told Live Science.

Yesterday's earthquake off the coast of Fukushima was centered about 80 miles (130 kilometers) southwest of the epicenter of the 9.0-magnitude Tohoku quake that struck in March 2011. This means the magnitude-6.9 temblor could be an aftershock of the more-powerful 2011 quake, according to seismologists.

"There's been a whole sequence [of aftershocks] since the 2011 earthquake," Smith said. "These enormously big earthquakes have aftershocks that can continue for tens to hundreds of years. It's very common."

The 2011 earthquake released hundreds of years of pent-up stress within the subduction zone and triggered an enormous tsunami that inundated the coastal Fukushima Daiichi Nuclear Power Plant, eventually causing a level 7 nuclear meltdown. While yesterday's quake was not as powerful as the Tohoku temblor, the entire region is still at risk of big earthquakes.

The Tohoku quake "was one of the biggest earthquakes we've recorded historically, but the fact is, the seismic hazard of the whole subduction zone is extremely high, so large earthquakes are more common there than other places," Smith said.

Earlier this year, in April, a magnitude-7.0 earthquake struck the Kumamoto region in southern Japan, two days after a 6.2-magnitude temblor shook the same area.

Original article on Live Science.

A magnitude-6.9 earthquake struck off the coast of Fukushima, Japan, today (Nov. 21), triggering a tsunami warning.

The earthquake, which was originally reported as a magnitude-7.3, struck around 6 a.m. local time on Nov. 22, about 23 miles (37 kilometers) southeast of Namie, Japan, the U.S. Geological Survey reported. A tsunami warning issued by the Japan Meteorological Agency has predicted wave heights of up to 10 feet (3 meters).

According to the Japan Meteorological Agency, a tsunami warning typically means damage due to tsunami waves is expected and residents should immediately evacuate coastal regions and riverside areas. These warnings also mean that tsunami waves are expected to hit repeatedly, and people should not leave safe ground until the warning is lifted. [Image Gallery: This Millennium's Destructive Earthquakes]

The area is no stranger to catastrophic quakes; on March 11, 2011, a magnitude-9.0 earthquake struck Japan. The so-called Tohoku quake, which released hundreds of years of pent-up stress at the subduction region where the Pacific Plate is diving beneath the Eurasian Plate, set off a massive tsunami with run-up heights of 128 feet (39 m) and inundation reaching 6 miles (9.7 km) inland.

The multistory waves inundated the coastal Fukushima Daiichi Nuclear Power Plant and triggered a level 7 nuclear meltdown. Four years after the quake, 230,000 people who lost their homes were still in temporary housing, according to Japan's Reconstruction Agency. Since the disaster, radioactive waste, such as cesium-134 and cesium-137, has floated across the Pacific Ocean and washed ashore on the West Coast of the U.S.

The epicenter of today's earthquake was about 80 miles (130 km) southwest of the 2011 Tohoku quake's epicenter, but that number can give a misleading impression of how far apart the two quakes occurred, said Don Blakeman, a geophysicist with the USGS in Golden, Colorado. With quakes as large as the 2011 earthquake, "the fault rips for many man tens of kilometers," Blakeman told Live Science. 

While the Japan Meteorological Agency issued a tsunami warning for the region around Fukushima and an advisory for the entire coastline of the country, the current quake is unlikely to trigger a Pacific-wide tsunami, Blakeman said. 

"This is a strike-slip earthquake," meaning that two sides of the fault move sideways relative to each other. "So, you don't get the vertical movement you need," Blakeman said.

Original article on Live Science.

They may have happened within days of one another, but the devastating earthquakes in Japan had nothing to do with the strong temblor that struck Ecuador over the weekend, experts say.

Both Japan and Ecuador are located along the so-called Pacific Ring of Fire, which spans the coasts lining the Pacific Ocean. The regions along the Ring of Fire are prone to earthquakes, but it's extremely rare for an earthquake on one side of the world to trigger earthquakes on the other, said Ross Stein, CEO and co-founder of Temblor.net, a free website and smartphone application that helps people understand locations' seismic risk.

For one thing, the earthquakes that hit Japan are a completely different type of quake than the one that struck Ecuador, Stein said. On April 14, a magnitude-6.2 earthquake hit southern Japan, and a day later, on April 15, a magnitude-7.0 earthquake struck the same region, according to the U.S. Geological Survey (USGS). [The 10 Biggest Earthquakes in History]

Both of these earthquakes were strike-slip earthquakes, Stein said, which occur when two parts of the Earth's crust slide against each other. The best way to imagine this is to place your hands together, with your fingers pointing away from your body, and slide your left hand forward and your right hand backward.

Both of these strike-slip earthquakes were shallow — about 6 to 8 miles (10 to 12 kilometers) deep — and both were destructive, killing more than 40 people in total, according to news sources. But the second quake was about 20 times stronger than the first, and released about 400,000 times more energy than the amount unleashed by the atomic bomb dropped on Nagasaki in 1945, Stein and Volkan Sevilgen, the other Temblor.net co-founder, wrote in a blog post.

These two earthquakes in Japan were likely related, Stein said. However, it's unclear whether the magnitude-6.2 earthquake was a foreshock of the magnitude-7.0 earthquake or the magnitude-7.0 earthquake was an aftershock of the magnitude-6.2 earthquake, Stein said.

"So far, the evidence suggests that both are true," the experts wrote in the blog post. Though it's rare for an aftershock to be larger than the main shock, it does happen, Stein told Live Science.

Regardless, the first earthquake made the faults near it more likely to rupture, which likely helped to trigger the second, larger earthquake, Stein said. 

Ecuador earthquake

On Saturday (April 16), merely a day after the second Japanese earthquake, a massive magnitude-7.8 earthquake rocked Muisne, Ecuador, the USGS reported. [Image Gallery: This Millennium's Destructive Earthquakes]

Unlike the strike-slip earthquakes in Japan, this one was a so-called megathrust quake, which occurs when one tectonic plate jams under another. In this case, the Nazca Plate is moving under the South American continent at a rate of about 2.2 to 2.4 inches (55 to 61 millimeters) a year, Stein and Sevilgen wrote in another blog post.

Almost 350 deaths have been reported from the Ecuador quake so far, CNN reported.

This isn't Muisne's first large earthquake. Another magnitude-7.8 earthquake hit almost the exact location in 1942, Stein said. In fact, given that the subduction rate is about 2.3 inches (60 mm) a year, and nearly 75 years have elapsed since the last large earthquake, it makes sense that this is a "repeat earthquake," Stein said.

But there's more to the story, he said. In 1906, Muisne experienced a magnitude-8.3 earthquake, so there may be other forces at work beyond a simple "repeat" event, he said.

"Considering that this site was part of the 10-times-larger event in 1906, it is particularly baffling," the experts wrote in the blog.

Even though the earthquake in Ecuador is unrelated to the two earthquakes in Japan, there is evidence that a gigantic earthquake can trigger others around the world. For instance, the magnitude-8.6 earthquake that struck the east Indian Ocean in 2012 is the largest strike-slip event on record, according to a 2012 study in the journal Nature, written by Stein and his colleagues.

After that massive earthquake, there was a nearly fivefold increase in earthquakes with a magnitude of 5.5 or greater for six days after the event, the researchers found.

"Those aftershocks tended to be strike-slip as well," Stein said. "It was mama calling to her kids."

Follow Laura Geggel on Twitter @LauraGeggel. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Whether it's moon phases, migrating bison or a particular type of weather, there are many ways people try to predict planetary catastrophes, such as earthquakes. None of these techniques actually work, but that doesn't stop armchair experts.

Ask a seismologist, however, and nearly all will say earthquake prediction is impossible. But two prominent researchers break the party line today (May 15) in an opinion piece published in the journal Science.

What's changed? Data from two big earthquakes — one that recently struck Chile, and Japan's 2011 monster — suggest it's possible to predict the largest quakes, the researchers say. [In Photos: This Millennium's Most Destructive Earthquakes]

The magnitude-8.1 terremoto (as Chileans say) offshore of Iquique, Chile, on April 1, followed about two weeks worth of smaller temblors that migrated along the fault toward its final breaking point. A similar pattern played out before the 2011 Tohoku earthquake in Japan, which measured magnitude 9.0.

"When the Chile earthquake happened, it was a bit of a jaw dropper for me," said Emily Brodsky, lead author of the Science Perspective and a seismologist at the University of California, Santa Cruz (UCSC). "What I took away from the whole experience was maybe my very deep, inbred cynicism [about predicting earthquakes] is unfounded."

When earthquakes come in bunches

Tracking swarms of earthquakes crawling along a fault could provide advance warning before damaging earthquakes strike, wrote Brodsky and her co-author Thorne Lay, also a UCSC seismologist.

But these kinds of swarms aren't isolated to Chile and Japan, and other scientists who watched the sequences play out are far from convinced. Researchers face one big hurdle in figuring out how to distinguish between foreshocks (earthquakes that lead to bigger quakes) and everyday earthquake clusters.

"The relevant question is: How many times did similar clusters of small quakes occur without a big quake following, and the answer is hundreds or thousands of times more often," said Robert Geller, a geophysicist at the University of Tokyo. "These authors are unjustifiably using the word 'prediction,' which should be reserved for data that would make it a real possibility to issue alarms," Geller said in an email interview.

Brodsky and Lay agree that it's hard to determine what is actually a foreshock. But they argue that the results from the Tohoku and Chile earthquakes are tantalizing enough to warrant investment in offshore seismic networks that could provide real-time data and potentially solve the problem. [In Pictures: Japan Earthquake & Tsunami]

"Distinct foreshock sequences before really big earthquakes have been observed a few times now, and that means we should take them seriously," Brodsky told Live Science's Our Amazing Planet.

Most countries view installing permanent seafloor seismometers as prohibitively expensive. Research ships to deploy the sensors don't come cheaply, and the monitors themselves require thousands of miles of cable and surface buoys to transmit data to shore. Adding a couple thousand seafloor stations could cost upwards of $1 billion, based on recent attempts. But whether or not such networks can predict earthquakes, scientists would love to see better offshore monitoring.

"There is a need to carry out more studies in subduction zones, because these regions remain largely unexplored," said Sergio Barrientos, director of the Seismological Service of the University of Chile, who led the national response to the recent earthquake swarm. Subduction zones, where two tectonic plates collide, unleash the most powerful earthquakes on the planet.

Prediction vs. forecast

Of course, scientists already provide earthquake warnings, but they don't use the "p-word." Rather, they call it earthquake forecasting, which gives the probability of an earthquake in a certain time period. In the United States, official forecasts often cover 30 years, because it's the average length of a home mortgage.

The difference between predictions and forecasts can be explained with a coin toss: Flip a coin, and call heads or tails. That's a prediction. But estimate how often you will land on heads or tails in the next five minutes? That's a forecast. Weather analogies can also help explain the difference. An earthquake prediction has a location and a date, like saying it will rain tomorrow in New York City. An earthquake forecast, on the other hand, is like saying there's a 30 percent chance of showers in the next five days.

Part of what makes earthquake forecasting successful is that it relies on geologic context, such as looking at where earthquakes happened in the past. Brodsky and Lay said such context is important to cases like Tohoku and Chile. Both earthquakes ruptured parts of faults that were what scientists called locked. No large earthquakes had occurred in either site for more than a century.

Combining similar geologic detective work with better offshore networks could finally lead to earthquake prediction, Brodsky and Lay said.

And that's where some researchers agree that progress is possible. "We may never get to the sort of deterministic prediction that some people think of as earthquake prediction," said Jeff McGuire, a geophysicist at the Woods Hole Oceanographic Institution in Woods Hole, Massachusetts. "However, I think in some tectonic regions, we are not that far from being able to make defensible statements about significant probability increases over time-scales of hours to weeks before the big earthquake happens."

Email Becky Oskin or follow her @beckyoskin. Follow us @OAPlanet, Facebook and Google+. Original article at Live Science's Our Amazing Planet.

How well a person recovers from traumatic events may depend on in part on their self-esteem, according to researchers who examined the effects of a major earthquake on the survivors' brains.

The researchers had conducted brain scans of university students for a study before the Great East Japan Earthquake struck in 2011. After the earthquake, they repeated the scans on 37 of the same people, and tracked stress-induced changes in their brains in the following months.

"Most importantly, what these findings show, is that the brain is dynamic — that it's responding to things that are going on in our environment, or things that are part of our personality," said Rajita Sinha, professor of psychiatry at Yale School of Medicine, who wasn't involved in the study. [Top 10 Mysteries of the Mind]

In the brain scans taken immediately after the incident, the researchers found a decrease in the volume of two brain regions, the hippocampus and orbitofrontal cortex, compared with the scans taken before the incident.

One year later, the researchers repeated the scans and found that the hippocampus continued to shrink, and people's levels of depression and anxiety had not improved.

However, other changes in the brain had reversed, the researchers found: The volume of the orbitofrontal cortex had increased. Moreover, this increase was correlated with survivors' self-esteem scores soon after the earthquake, according to the study published today (April 29) in the journal Molecular Psychiatry.

The findings suggest that structural changes in the brain following a stressful event are not static, but dynamic, throughout one's lifetime, study researcher neuroscientist Atsushi Sekiguchi and his colleagues wrote in their study.

It is possible that people with higher self-esteem, which is important to a person's resilience in the face of stressful life events, can regulate emotional distress more successfully, and this is reflected in their brain changes, the researchers said.

The researchers noted that the study cannot show a cause-and-effect relationship, and it is difficult to know whether it really is higher self-esteem that results in better recovery from trauma, or something else that is related to self-esteem has a role.

Also, more research is needed to confirm that the stress-induced alterations in brain structure are indeed reversible, the researchers said.

But previous studies have found that highly stressful events can cause structural changes in both the orbitofrontal cortex and hippocampus.

"These regions are part of the network that takes the hit in a traumatic event, said Sinha, who studies the effects of stress on the brain.

The reason why the hippocampus and orbitofrontal regions are vulnerable to stress may lie in their biology.

"These regions are more affected because both respond to neurochemicals that are involved in the stress response, like cortisol, and also norepinephrine, which is our fight-or-flight neurochemical," Sinha told Live Science. "So when there's high impact of stress or trauma, you can imagine that there's a flooding with these neurochemicals, and that can affect the brain cells."

Email Bahar Gholipour. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.  

Debris from the deadly tsunami that struck Japan in 2011 is drifting across the Pacific Ocean toward North America, and will likely continue to wash onto North American shores over the next few years, according to the U.S. National Oceanic and Atmospheric Administration (NOAA).

"A significant amount of debris has already arrived on U.S. and Canadian shores, and it will likely continue arriving in the same scattered way over the next several years," NOAA officials said in a statement. "As we get further into the fall and winter storm season, NOAA and partners are expecting to see more debris coming ashore in North America, including tsunami debris mixed in with the 'normal' marine debris that we see every year."

On March 11, 2011, a 9.0-magnitude earthquake struck off the east coast of Japan, triggering a devastating tsunami that killed more than 15,000 people and caused widespread destruction.

An estimated 5 million tons of debris — everything from boats to kitchen appliances — was swept into the Pacific Ocean by the tsunami. Roughly 70 percent of this detritus likely sank near the coast of Japan, but the rest (some 1.5 million tons) is scattered in the water, and has been drifting toward North America. [Tracking Tsunami Debris (Infographic)]

Recent reports suggested an island of debris the size of Texas was floating toward North America, but NOAA officials were quick to set the record straight.

"At this point, nearly three years after the earthquake and tsunami struck Japan, whatever debris remains floating is very spread out," NOAA officials said. "It is spread out so much that you could fly a plane over the Pacific Ocean and not see any debris, since it is spread over a huge area, and most of the debris is small, hard-to-see objects."

NOAA has been tracking the debris since 2011, and the agency recently updated its models to include the effects of wind on the debris, which vary depending on the material and how much of the object's surface is above water.

But there are still many unknowns surrounding where all that stuff will end up, and when pieces of debris may arrive on American shores.

"This new modeling effort gives us a better understanding of where the debris may have traveled to date, but it does not predict where it will go in the future or how fast it will drift," NOAA officials wrote in an update. "The new model takes into account that wind may move items at different speeds based on how high or low materials sit in the water."

Earlier this year, a small Japanese skiff washed ashore near Crescent City, Calif. Nearly 30 other pieces of debris — including fishing buoys, a soccer ball, other small boats and even two floating docks — have washed up in Oregon, Washington, Hawaii, Alaska and British Columbia.

The docks that were swept ashore in Washington and Oregon contained massive amounts of marine life, which required decontamination in order to prevent non-native invasive species from gaining a foothold along the U.S. coast.

Follow Denise Chow on Twitter @denisechow. Follow LiveScience @livescience, Facebook & Google+. Original article on LiveScience.

One of the storage tanks from Japan's Fukushima nuclear power plant damaged by the 2011 earthquake and tsunami has leaked about 300 tons of radioactive water, officials report.

Investigation is ongoing, but Tokyo Electric Power Co. (TEPCO) said the leak may have occurred through a seam on the tank or valve on a surrounding gutter. The radiation is about five times the annual exposure limit for plant workers. TEPCO said seawater contamination is not an immediate concern, because the tank is 330 feet (100 meters) from the coast, but Japan's nuclear watchdog said the leaked water could enter the ocean by a drain gutter, The New York Times reported.

Four other tanks had similar leaks in 2012, but this leak is the worst one yet. Sandbags were piled around to soak up the flow, but radioactive water still soaked into the ground, TEPCO said. Workers are racing to pump the water out of the puddle and tank before the arrival of heavy rain predicted for later in the day.

Follow Tanya Lewis on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on LiveScience.

A barrel-size black plastic float torn loose by the 2011 Japan tsunami may have been tossed into a Canadian forest by a second tsunami in 2012, researchers say.

Though the hollow float hasn't been officially confirmed as tsunami debris, it is identical to a float embossed with the name "Musashi" found in the U.S. Dungeness National Wildlife Refuge in May 2012, the researchers said. A similar float was traced to an oyster farm in northeast Japan. The debris from the devastating 2011 tsunami has washed up from Alaska to California to Hawaii.

"This is a float that was caught up in the tsunami from Japan, so it is doubly tsunami debris," seismologist Alison Bird of the Geological Survey of Canada said at the Seismological Society of America's annual meeting on April 19. The float was discovered on Moresby Island in British Columbia. The island is part of Haida Gwaii, once called the Queen Charlotte Islands. [Infographic: Tracking Japan's Tsunami Debris]

Second tsunami

The magnitude-7.7 Haida Gwaii earthquake on Oct. 27, 2012, triggered the tsunami, which raced far up western inlets on Moresby Island and Graham Island, but caused little damage on either island's populated eastern side. The powerful wave also sped straight to Hawaii, hitting with a maximum height of 2.5 feet (76 centimeters) and no serious flooding or damage.

The tsunami run-up, which measures how far water surges onshore, was as much as 22 feet (7 meters) in protected bays on the islands' west coasts, Gary Rogers, a Geological Survey of Canada scientist, said at the meeting. (A hurricane-force storm hit the islands just after the earthquake, destroying any record of the tsunami except in protected areas, Rogers said.)

Lucinda Leonard, the Geological Survey scientist who discovered the fishing float, also found dead fish in the forest moss and logs shoved out of place by the tsunami. Seaweed was wrapped around tree branches up to 8 feet (2.5 m) high in Sunday Inlet, near where the float ended its journey.

A strange earthquake

Geologists are still puzzling over the unusual Haida Gwaii earthquake, which surprised scientists because of its unexpected style. Understanding what caused the quake will help them forecast the region's earthquake and tsunami hazards.

Two tectonic plates meet west of Haida Gwaii: the Pacific plate and the North America plate. A strikingly obvious strike-slip fault, the Queen Charlotte fault, has been thought to mark the boundary between the two plates. Strike-slip faults are mostly vertical fractures where two blocks of Earth's crust slide past each other horizontally. The Queen Charlotte unleashed Canada's largest recorded temblors in 1949, a magnitude 8.1.

But the 2012 earthquake was a thrust earthquake, on a previously unknown fault west of the Queen Charlotte fault. The thrust fault hides under a giant pile of sediments. In a thrust quake, two blocks of crust move toward each other, like in subduction zones.

Rethinking the plate boundary

Given the region's ancient tectonic history, there could be a remnant piece of oceanic crust sliding down beneath the southern part of Haida Gwaii, Rogers said. There is some evidence for this from seismic waves, which change their speed when they pass through old, cold crust sitting in hotter mantle rocks. (Earth's mantle lies beneath the crust.)

"It all looks very much like a subduction zone, given the down-bowing of oceanic crust and the accretionary prism [of sediments]," Rogers said. The Pacific plate could be subducting under Haida Gwaii, and thus the North American plate, as far north as the middle of Moresby Island, he said.

Now, scientists want to figure out if the plate boundary is strike-slip or subduction, or a combination of both. They also want to know if there could be bigger earthquakes, and what happens to the Queen Charlotte strike-slip fault when it meets this mysterious new fault. [7 Ways the Earth Changes in the Blink of an Eye]

"If this is some sort of remnant subduction, are we always going to get a small amount of strike-slip with more thrust events?" David Oglesby, a seismologist at the University of California, Riverside, said at the meeting. "It does raise the possibility that you could get significant slip down there."

Email Becky Oskin or follow her @beckyoskin. Follow us @OAPlanet, Facebook & Google+. Original article on LiveScience's OurAmazingPlanet.

A barrel-size black plastic float torn loose by the 2011 Japan tsunami may have been tossed into a Canadian forest by a second tsunami in 2012, researchers say.

Though the hollow float hasn't been officially confirmed as tsunami debris, it is identical to a float embossed with the name "Musashi" found in the U.S. Dungeness National Wildlife Refuge in May 2012, the researchers said. A similar float was traced to an oyster farm in northeast Japan. The debris from the devastating 2011 tsunami has washed up from Alaska to California to Hawaii.

"This is a float that was caught up in the tsunami from Japan, so it is doubly tsunami debris," seismologist Alison Bird of the Geological Survey of Canada said at the Seismological Society of America's annual meeting on April 19. The float was discovered on Moresby Island in British Columbia. The island is part of Haida Gwaii, once called the Queen Charlotte Islands. [Infographic: Tracking Japan's Tsunami Debris]

Second tsunami

The magnitude-7.7 Haida Gwaii earthquake on Oct. 27, 2012, triggered the tsunami, which raced far up western inlets on Moresby Island and Graham Island, but caused little damage on either island's populated eastern side. The powerful wave also sped straight to Hawaii, hitting with a maximum height of 2.5 feet (76 centimeters) and no serious flooding or damage.

The tsunami run-up, which measures how far water surges onshore, was as much as 22 feet (7 meters) in protected bays on the islands' west coasts, Gary Rogers, a Geological Survey of Canada scientist, said at the meeting. (A hurricane-force storm hit the islands just after the earthquake, destroying any record of the tsunami except in protected areas, Rogers said.)

Lucinda Leonard, the Geological Survey scientist who discovered the fishing float, also found dead fish in the forest moss and logs shoved out of place by the tsunami. Seaweed was wrapped around tree branches up to 8 feet (2.5 m) high in Sunday Inlet, near where the float ended its journey.

A strange earthquake

Geologists are still puzzling over the unusual Haida Gwaii earthquake, which surprised scientists because of its unexpected style. Understanding what caused the quake will help them forecast the region's earthquake and tsunami hazards.

Two tectonic plates meet west of Haida Gwaii: the Pacific plate and the North America plate. A strikingly obvious strike-slip fault, the Queen Charlotte fault, has been thought to mark the boundary between the two plates. Strike-slip faults are mostly vertical fractures where two blocks of Earth's crust slide past each other horizontally. The Queen Charlotte unleashed Canada's largest recorded temblors in 1949, a magnitude 8.1.

But the 2012 earthquake was a thrust earthquake, on a previously unknown fault west of the Queen Charlotte fault. The thrust fault hides under a giant pile of sediments. In a thrust quake, two blocks of crust move toward each other, like in subduction zones.

Rethinking the plate boundary

Given the region's ancient tectonic history, there could be a remnant piece of oceanic crust sliding down beneath the southern part of Haida Gwaii, Rogers said. There is some evidence for this from seismic waves, which change their speed when they pass through old, cold crust

sitting in hotter mantle rocks. (Earth's mantle lies beneath the crust.)

"It all looks very much like a subduction zone, given the down-bowing of oceanic crust and the accretionary prism [of sediments]," Rogers said. The Pacific plate could be subducting under Haida Gwaii, and thus the North American plate, as far north as the middle of Moresby Island, he said.

Now, scientists want to figure out if the plate boundary is strike-slip or subduction, or a combination of both. They also want to know if there could be bigger earthquakes, and what happens to the Queen Charlotte strike-slip fault when it meets this mysterious new fault. [7 Ways the Earth Changes in the Blink of an Eye]

"If this is some sort of remnant subduction, are we always going to get a small amount of strike-slip with more thrust events?" David Oglesby, a seismologist at the University of California, Riverside, said at the meeting. "It does raise the possibility that you could get significant slip down there."

Email Becky Oskin or follow her @beckyoskin. Follow us @OAPlanet, Facebook & Google+. Original article on LiveScience's OurAmazingPlanet.

SALT LAKE CITY — When the world shakes, so does Antarctica's ice, according to a study presented here April 19 at the Seismological Society of America's annual meeting.

Icequakes are vibrations in glaciers and ice sheets (the massive expanses of glacial ice that cover Antarctica and Greenland). From small creaks and groans to sudden slips equal to a magnitude-7 earthquake, the shaking signals movement in the ice.

Scientists discovered that big earthquakes, including Japan's 2011 Tohoku quake and Chile's 2010 Maule temblor, set off icequakes across Antarctica, just as they triggered earthquakes on land.

"We see pretty clear evidence of triggering [in Antarctica]," said Jake Walter, a geophysicist at Georgia Tech.

The icequakes started after a type of rolling earthquake wave called surface waves (also known as Rayleigh waves) raced through the frozen ice, Walter said. After the two recent major temblors, earthquake monitors picked up a spike in icequakes, which typically hit throughout the day as the ice shifts.

Walter suspects the shaking could shift crevasses or adjust the ice above subglacial rivers, both known icequake triggers.

The research team is also taking a closer look at the effects of earthquakes on the Whillans Ice Stream, a fast-moving ice river that flows to the Ross Sea. Whillans — where, this year, researchers recovered the first signs of life from a buried subglacial lake — surges toward the sea two times a day in stick-slip motion, much in the way earthquake faults move. Early results suggest that earthquakes elsewhere on the planet can trigger these sudden slips, Walter said.

Email Becky Oskin or follow her @beckyoskin. Follow us @OAPlanet, Facebook & Google+. Original article on LiveScience's OurAmazingPlanet.

A curved piece of wood, painted red, removed from a beach in Oregon may be a piece of a shrine set to sea by the 2011 Japanese tsunami.

The debris has not yet been confirmed as originating from the tsunami, but the chief public relations officer of the Association of Shinto Shrines told Oregon Public Broadcasting (OPB) that the wood appears to be part of a torii, a gate over the entrance of a Shinto shrine.

If so, the driftwood would hardly be the first object to make its way across the Pacific in the two years since the tsunami hit, killing more than 15,000 people. The National Oceanic and Atmospheric Administration (NOAA) has confirmed 21 pieces of debris from the tsunami on Pacific isles and the North American coastline. These confirmed pieces include docks, boats and other objects with serial numbers or identifying marks.

Meanwhile, the agency has received reports of more than 1,000 more pieces of debris that may be tsunami-related, and materials such as housing insulation have shown up in larger-than-usual quantities in Alaska and Hawaii. Debris from Japan is a constant visitor to North American shores, so most of the items will likely never be definitively linked to the tsunami, though scientists suspect they are related.

Tsunami damage

The Japanese government estimates that the March 2011 tsunami pulled some 5 million tons of rubble into the Pacific. Most of that debris sank off the coast of Japan, but approximately 1.5 million tons moved farther out to sea. No one knows how much is still drifting.

Oregon has seen its fair share of debris, including an enormous dock covered in sea life that washed up near Newport, Ore., in June 2012. This month alone, several small boats suspected to be tsunami debris washed up onshore, according to the Oregon Department of Fish and Wildlife. The boats were taken to landfills. [See Images of the Beached Tsunami Dock]

According to OPB, Judson Randall of Oceanside, Ore., spotted the possible Shinto gate on Friday, March 22.

"My first thought was that it was something from the tsunami, because it had all that marine life on it and it looked man-made," Randall told the news agency. "It was a chilling thought."

Lost shrines

The religious symbolism of the possible shrine fragment could make it more sensitive than other tsunami debris. Shinto is the indigenous religion of Japan, and the Association of Shinto Shrines oversees about 80,000 shrines spread throughout the country. More than 4,500 Shinto shrines were damaged or destroyed by the tsunami or rendered unusable by radiation from the Fukushima nuclear meltdown after the 2011 disaster, according to the Washington Post.

The possible torii has been removed from the beach. Officials are awaiting response from the Japanese government to decide what to do with the object.

Follow Stephanie Pappas on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on LiveScience.com.

Tsunami Dock

Officials found this 65-foot (20 meter) dock on a remote beach in Olympic National Park, Washington on Dec. 18. Because of the dock's remote location, crews could not begin the removal process until March 19, 2013.

Reaching the Dock

A crew makes the rugged trek to the dock in Olympic National Park on Dec. 21, 2012.

Dock Sampling

A worker takes samples from the dock on Dec. 21, 2012.

Tracking Buoy

Crews attached a tracking buoy on Dec. 21, 2012 to make sure the dock wouldn't be lost if the current swept it out to sea.

Dock in Surf

The Japanese dock sits in the surf on a remote beach in Olympic National Park.

Beached Dock

Rough surf and swollen creeks kept crews from the dock. Helicopters will be used to remove pieces of the dock from the beach.

Helicopter View

A view of the dock on Dec. 18, 2012 from helicopter.

Trek to the Dock

Reaching the dock on Dec. 21, 2012 required a trek across fallen logs.

Crossing the Creek

The trip to the dock also involved a deep creek crossing.

Dock Damage

Damage to the tsunami dock on the Washington beach.

January Dock

Workers atop the dock on January 3, 2013.

More Dock Damage

The waves caused more damage to the dock during late December 2012.

Dock on the Beach

The dock on the beach in January 2013.

Dock Species

Scientists are analyzing some 50 species found living on the dock.

Losing Styrofoam

On Jan. 3, 2013, the dock appeared to be losing Styrofoam, a potential hazard to marine life.

Dock Removal

Preparations for dock removal begin on March 18, 2013. Sand and stones have built up around the dock, requiring excavation.

Removal Plan

This illustration shows the plan to remove the dock.

Dock Excavation

Workers excavate around the beached tsunami dock.

Dock Removal Process

Cutting the face off the three south-facing compartments of the dock with a wire saw.

Sawing the Dock

A worker uses a walk-behind saw to cut the top of the dock.

Predicting flooding from tsunamis saves lives. After the Tohoku earthquake two years ago, alerts issued in advance of the monster waves saved thousands of people in Japan and other countries circling the Pacific Ocean.

But for many in Japan, the forecasts failed. Models could not predict how far inland the tsunami would rush, leading to thousands of deaths.

A new study suggests the devastating effects were heavily dependent on more than just the enormous size of the magnitude-9.0 earthquake that triggered the tsunami. The distance of the coast from the point where the earthquake ruptured also played a role. At just the right spacing from a coastline, a tsunami wave can focus its energy at the coast, sweeping farther inland than current models predict, researchers found.

"The effect of focusing that we have described can happen at a coastline directly in front of the [earthquake] source, where historically [the] most fatalities occur during tsunamis," said Vasily Titov, director of the National Oceanic and Atmospheric Administration's Center for Tsunami Research in Seattle and a study co-author. [Waves of Destruction: History's Biggest Tsunamis]

The results could improve computer models that predict tsunami flooding, the researchers said. The findings appear in the Feb. 27 issue of the journal Proceedings of the Royal Society A.

"We are still trying to understand the implications," said Costas Synolakis, a tsunami expert at the University of Southern California in Los Angeles and another co-author of the study. "But it is clear that our findings will make it easier to identify locales that are tsunami magnets, and thus help save lives in future events," he said in a statement.

Subduction zones and tsunamis

The Tohoku earthquake struck on a subduction zone, an area at which two of Earth's tectonic plates crash together and one slides beneath the other. Notorious tsunami generators, earthquakes in these areas lift the seafloor on one side of the subduction zone and drop it down on the other side. Such elevation changes give the water above a giant push, creating a tsunami.

Each subduction zone quake generates multiple waves: a crest wave, above the uplifted seafloor, and a trough wave, from the dropped seafloor. The trough side starts with a big dip, or trough, while the crest side leads with a swell, or crest.

So a tsunami is actually a series of waves. Both the crest and trough wave sides propagate in both directions; the crest side sends waves both out into the open ocean and towards the shore, as does the trough side.

Subduction zones are always oriented so the trough side of the tsunami is closer to, and thus the first to advance towards, the nearest shoreline, Costas noted. The international research team created a computer model simulating a subduction zone tsunami. The model showed that waves from the crest side decrease in height continuously as they travel through the ocean, then grow in height near the shore, an effect called shoaling.

But trough-side waves vary in height as they travel through the ocean, the study found. At a certain distance from the earthquake source, called the focusing point, one wave from the crest side overtakes two waves from the trough side. The combined wave energy makes the tsunami even taller, though it quickly dissipates.

"The trough-wave side first decreases, then increases in height, then decreases again," Costas told OurAmazingPlanet.

The Goldilocks effect

"This means the distance between the earthquake zone and the shoreline is extremely important," Costas said. Sometimes, a trough-wave tsunami will come onshore right at its highest peak, driving water farther inland than expected.

But if the distance between a tsunami-generating earthquake and a shoreline is very short, focusing does not have time to occur. If the distance is long, focusing takes place far from the shore. If the distance between the subduction zone and the nearby land is just right, then focusing amplifies the wave height, making it bigger.

The team observed this effect in their model of the 2011 Tohoku earthquake. The same effect occurred in Central Java, which was struck by a tsunami in 2006, and in Papua New Guinea, where 2,200 people died in a 1998 tsunami.

Email Becky Oskin or follow her @beckyoskin. Follow us @OAPlanet, Facebook or Google+. Original article on LiveScience's OurAmazingPlanet.

Two years after a deadly tsunami swept ashore in Japan, killing more than 15,000 people, solemn reminders of the disaster are still washing ashore in Hawaii and along the Pacific coast of North America.

The tsunami debris, sometimes identifiable by serial numbers, includes boats, docks, appliance parts and fishing buoys. Though harder to trace back to a particular source, an uptick in Styrofoam and housing materials may also originate from the March 2011 wave.

"This has been a very unprecedented event," said Nancy Wallace, the director of the marine debris program at the National Oceanic and Atmospheric Administration (NOAA). The agency has been tracking the debris, which can pose a navigation hazard to boats and an entanglement or choking hazard to wildlife. The process has given scientists a better understanding of how debris travels, Wallace told LiveScience, but no one knows how much is yet to come ashore.

"We just don't know how much debris is still floating in the water," Wallace said. "We don't know how much has sunk. What we're trying to be as focused on as possible is trying to prepare for it as best we can."

Unusual debris

So far, NOAA has confirmed 21 pieces of debris from the Japan tsunami on U.S. shores. The most recent piece, confirmed by the Consulate of Japan on Feb. 5, was a large, yellow buoy found off the Hawaiian island of Kauai. (The agency has received more than 1,000 debris reports, but many items cannot be definitively linked to the tsunami.)

Other confirmed items that have washed up include a soccer ball in Washington State, a 35-foot (11 meters) steel tank in British Columbia and multiple small, derelict boats.

Two floating docks beached themselves in Washington and Oregon, both harboring massive amounts of marine life and requiring decontamination to prevent invasive species from establishing themselves on the U.S. coastline. [Images: Beached Japanese Dock]

Sometimes, a sudden influx of a particular item strongly suggests that it is tsunami-related, even in the absence of other evidence. Styrofoam and other housing materials, for example, have been showing up in bulk in Alaska and Hawaii, said Nicholas Mallos, an ocean debris specialist at the non-profit Ocean Conservancy.

"Styrofoam has shown up in some places in quantities 30 times historical abundances," Mallos told LiveScience.  

Tracking the debris

The debris slowly making its way across the Pacific to North America is only a fraction of the estimated 5 million tons of rubble and other materials swept into the sea by the tsunami, according to Japanese government estimates. Approximately 70 percent of the debris sunk off of Japan's coast, leaving 1.5 million tons to float across the ocean. How much of that is still floating is anybody's guess. [Tracking Tsunami Debris (Infographic)]

NOAA works with fishing vessels and commercial shippers, relying on eyewitness reports of debris in the open ocean. Early on, Wallace said, the agency tried to monitor the debris by satellite, but soon found that the material wasn't visible for very long. As the debris fields dispersed and some of it sank, the remaining pieces were too small to see from orbit.

Models of debris flow have proved more useful, though the motion of the matter depends heavily on wind and water currents. Using historical climate data, scientists can make an approximation, Wallace said, but the models were greatly improved when researchers put the real-world current and wind conditions into the system. Unfortunately, that means that while researchers are good at telling where the debris is likely located now, they're not as clear on where it's going.

"There's a large amount of uncertainty," Wallace said.

Humans dump massive amounts of debris into the ocean on a regular basis, the Ocean Conservancy's Mallos said. There are no good numbers on what percentage of the debris currently in the sea comes from the tsunami versus from everyday garbage and abandoned fishing gear. Working to reduce this everyday junk, by decreasing consumer waste, for example, will make the oceans more resilient in the face of unavoidable debris disasters like tsunamis, Mallos said.

Another thing researchers don't know: the impact of all that debris that may never reach shore.

"Very little research has been done at mid-water depths, and particularly on the seafloor, as to what extent of debris abundance is there and what particular ecological impacts debris has on those marine environments," Mallos said.

Meanwhile, experts expect trickles of tsunami debris to continue to wash onto American shores for the next few years.

"Things can get caught up in eddies and gyres for awhile and then get spit out, so it could really be years that the debris is out there," Wallace said. "We hope that we've seen most of it, but it's just so hard to tell."

Follow Stephanie Pappas @sipappas. Follow us on Twitter @livescience, Facebook or Google+. Original article on LiveScience.com.

An earthquake of preliminary magnitude 6.9 struck the northern island of Hokkaido, Japan today, according to the U.S. Geological Survey (USGS). As of this writing, there were no reports of significant damage and no tsunami was expected.

The temblor's epicenter was 68 miles (109 km) from Kushiro and 525 miles (844 km) North-Northeast of Tokyo. It originated deep within the Earth’s crust, the USGS reports. Earlier reports had put the quake at magnitude 6.4. The USGS frequently updates the magnitude of an event after more data is analyzed.

A quake of this size is capable of causing considerable damage and are often followed by aftershocks. But the damage caused by any single event depends on the quake's depth, proximity to populated areas, building standards in the region, as well as the type of earthquake.

Today's earthquake originated 64 miles (103.1km) below the surface. The event occurred along what’s known as the Kuril-Kamchatka arc in the Pacific Rim, among the most volatile regions of the planet.

An earthquake's magnitude is a measure of the energy released at the source. It is just one predictor of the shaking that may ensue, which is affected by local and regional geology. Scientists know in a general sense what causes Earthquakes but are unable to predict specific quakes.

This article will be updated if significant additional information becomes available. Find more earthquake news here.

Was the 7.3-magnitude earthquake that struck today (Dec. 7) east of Sendai, Japan, in any way related to last year's enormous, 9.0 earthquake?

It's too early to tell definitively, said U.S. Geological Survey (USGS) geophysicist Jessica Turner, but the quake did happen in the "aftershock zone" of the March 2011 Tohoku earthquake. This zone is an area on the ocean floor that the 2011 quake physically moved and where more than 5,000 aftershocks have been recorded, according to the USGS.

Scientists say it's quite possible for aftershocks to arrive so late. "It's very normal to have aftershocks more than a year later," Turner told OurAmazingPlanet. It's debatable how long aftershocks can occur following earthquakes, however. But last year's monster temblor released so much energy that it wouldn't be surprising if the Earth is still adjusting, Turner said.

In general, such adjustments cause aftershocks, as the earth attempts to "get back to normal," Turner said. "It's going to take a long time for the Earth to get back to the background level of seismicity after last year's event," she said.

The March 2011 quake and subsequent tsunami killed nearly 20,000 people and caused a nuclear crisis when the Fukushima-Daiichi nuclear plant was destroyed, leaking radiation into the atmosphere and the ocean. [In Pictures: Japan Earthquake & Tsunami]

Today's earthquake, with a preliminary magnitude of 7.3, was caused by reversing faulting, in which the Pacific Plate subducts, or moves underneath the Eurasian plate, Turner said. The plate-boundary region surrounding the site of today's quake hosts moderate to large earthquakes fairly regularly. Over the past 40 years, 12 earthquakes of magnitude-7.0 or greater have occurred within 155 miles (250 kilometers) of the site, according to the USGS.

The temblor's epicenter was 152 miles (245 km) southeast of Kamaishi, Japan. It originated 22.4 miles (36.1 km) below the Earth's surface and struck at 5:18 p.m. local time (3:18 a.m. ET).

The powerful quake shook buildings as far away as Tokyo and triggered a 3.3-foot (1-meter) tsunami in an area devastated by last year's Fukushima disaster, according to news reports. (If you felt any shaking from the earthquake, you can tell the USGS here.)

Fortunately, today's earthquake hasn't caused any major injuries or destruction, Turner said.

Reach Douglas Main at dmain@techmedianetwork.com. Follow him on Twitter @Douglas_Main. Follow OurAmazingPlanet on Twitter @OAPlanet. We're also on Facebook and Google+.

People with weak connections in certain parts of their brains may be at increased risk for anxiety or post-traumatic stress disorder (PTSD) after a traumatic experience, a new study from Japan suggests.

The findings could one day allow researchers to predict which people will react especially severely to traumatic events, the researchers say.

Previous research has shown that the brains of people with PTSD differ from those without the condition. For instance, certain brain areas are smaller in people with PTSD, compared with people who've experienced traumatic events, but who didn't develop the condition. However, it has not been clear which brain features might put people at risk for PTSD, and which are instead a result of the condition.

In the new study, researchers analyzed information from 30 Japanese adolescents who experienced the 2011 earthquake that devastated parts of the country. The researchers had scanned the teens' brains before the earthquake, in connection with other studies. The subjects allowed researchers to reexamine their brains after the disaster.

The teens also completed a questionnaire after the earthquake to gauge their levels of anxiety. High anxiety after a trauma can indicate emerging PTSD, said study researcher Dr. Atsushi Sekiguchi, of Tohoku University.

The researchers specifically looked at changes to the brain's white matter, tissue that forms "cables" in the brain, or connections that allow brain areas to communicate with each other.

Participants who had weak connections in the front, right section of the brain before the disaster were more likely to have high levels of anxiety after the earthquake hit, the researchers said.

It might be possible to apply this finding to military personnel, to predict PTSD vulnerabilities before deployment, Sekiguchi said.

The researchers also identified brain changes that appeared to be brought on by the disaster. Strong connections in the front, left section of the subjects’ brains after the disaster were linked to higher post-disaster anxiety.

These brain areas are involved in processing fear and anxiety, and in regulating emotions, Sekiguchi said. The connections may be strengthened in these areas because survivors with high anxiety are frequently accessing them, Sekiguchi said.

These insights into brain features may allow researchers to quickly identify people who are developing PTSD after a disaster, Sekiguchi said.

However, much more research is needed before scans looking at the strength of brain connections could be used to predict PTSD, or identify people with the condition after a traumatic event, Sekiguchi said. Right now, the "threshold" that would indicate a person is at increased risk of PTSD is not known, Sekiguchi said.

The study was presented this week at the annual meeting of the Society for Neuroscience in New Orleans.

Pass it on: Weak connections in certain parts of their brain may put people at risk for PTSD.

Follow Rachael Rettner on Twitter @RachaelRettner, or MyHealthNewsDaily @MyHealth_MHND. We're also on Facebook & Google+.

Mysterious small tremors in the most earthquake-prone areas on Earthmay be the cause of surprisingly large tsunamis, researchers say.

These findings might also shed light on the huge tsunami generated by the disastrous magnitude 9.0 quake that hit Japan in 2011.

Nearly all of the 10 largest recorded earthquakes on Earth happened along subduction zones, where one of the tectonic plates making up the planet's surface is diving beneath another. The shallow regions of these zones are often not seismically active by themselves, but occasionally strange tremors are recorded from these locales that are rich in very-low-frequency seismic waves.

These shallow areas also seem to be home to so-called tsunami earthquakes, which generate tsunamis far stronger than one would expect for the amount of seismic energy they release. The Keicho quake of 1605 that caused disastrous tsunamis in Japan and killed thousands might have been one such earthquake.

To see if there were any links between the very-low-frequency events and tsunami earthquakes seen in the shallows of subduction zones, scientists in Japan used three ocean-bottom seismometers to analyze a swarm of very-low-frequency events in 2009. These occurred in the shallowest parts of the Nankai Trough, a part of a subduction zone near southwestern Japan that is rocked by giant earthquakes every century or so — most recently in 1946, when a magnitude 8.2 event killed an estimated 1,300 people.

The researchers discovered that the very-low-frequency quakes — ranging from magnitudes of 3.8 to 4.9 — can last 30 to 100 seconds. This is unusually long when compared with the 1-to-2 second duration of ordinary earthquakes with comparable magnitudes.

Although these very-low-frequency quakes get their name from seismic waves detected on land, the researchers discovered these events are actually rich in high-frequency waves as well. High-frequency waves tend to weaken with distance as they go through matter, which is why land seismometers did not detect these waves but ocean seismometers closer to the quakes did. The long duration of the quakes and the high-frequency waves now seen from them suggest these events may be caused by fluid seeping into fractures in the rock, making it easier for parts of the earth to slip past each other and generate tsunami earthquakes.

These findings suggest that authorities should keep a closer eye on the shallow areas of subduction zones. For instance, the huge tsunamis generated by the magnitude 9.0 quake that struck Japan in 2011 might be due in significant part to a slip in the shallow parts of the Japan Trench lying east of the country's main island.

"It is very important for us to monitor continuously seismic activities close to the trench," researcher Hiroko Sugioka, a seismologist at the Japan Agency for Marine-Earth Science and Technology at Yokosuka, told OurAmazingPlanet. "It is mitigation against unexpectedly large tsunami disasters."

The scientists detailed their findings online May 6 in the journal Nature Geoscience.

Follow OurAmazingPlanet for the latest in Earth science and exploration news on Twitter @OAPlanet and on Facebook.

Devastating Waves

These series of traveling ocean waves are primarily generated in association with underwater earthquakes (though underwater volcanic eruptions and landslides can also trigger a tsunami). In the deep ocean, the waves can reach hundreds of miles or more from wave crest to wave crest and can exceed speeds of 500 miles per hour (805 kilometers per hour). And they're sneaky, unable to be felt even aboard ships, and undetectable from the air.

Here are some of the biggest, most destructive and deadliest tsunamis on record.

The Orphan Tsunami

Around midnight on Jan. 27, 1700, a mysterious tsunami swept through several villages on the eastern coast of Japan. The waves reached as high as 12 feet and flooded rice paddies, washed away buildings and damaged fishing shacks and salt kilns. The tsunami struck not only without warning, but without an apparent cause, leading to its "orphan tsunami" moniker. Then in 2005, an international team of scientists and scholars has linked the orphan tsunami to a massive earthquake that struck a region in North America called Cascadia. [Read full story on the orphan tsunami]

8,000 Years Ago ...

A volcano-triggered avalanche in Sicily 8,000 years ago that crashed into the sea at 200 mph, generated a devastating tsunami that spread across the entire Mediterranean Sea. (The avalanche sent tumbling into the sea enough material to cover the entire island of Manhattan in a layer of debris thicker than the Empire State Building is tall.) Though no historical records of the event exist — only geological records — scientists say the tsunami was taller than 10-story building. [Read full story on the Sicily tsunami]

The Great Lisbon Earthquake

On Nov. 1, 1755, a colossal earthquake centered in the Atlantic Ocean — and whose three jolts of shaking lasted 10 minutes — destroyed Lisbon, Portugal, and rocked much of Europe, people took refuge by boat. A tsunami ensued, as did great fires. Altogether, the event killed more than 60,000 people.

(Shown here, a copperplate image showing the mayhem that ensued after the earthquake and tsunami rocked Lisbon.)

Krakatoa Tsunami

On Aug. 27, 1883, eruptions from the Krakatoa volcano fueled a tsunami that drowned 36,000 people in the Indonesian Islands of western Java and southern Sumatra. The strength of the waves pushed coral blocks as large as 600 tons onto the shore.

The Sanriku Tsunami

On June 15, 1896, waves as high as 100 feet (30 meters), spawned by an earthquake that struck Honshu, swept the east coast of Japan. And as is often the case, the waves seemed to come from nowhere. "Fishermen twenty miles out to sea didn't notice the wave pass under their boats because it only had a height at the time of about fifteen inches," according to a website run by the University of Hawaii. "They were totally unprepared for the devastation that awaited them when they returned to the port of Sanriku." Some 27,000 people died.

Lituya Bay

On the night of July 7, 1958, a magnitude-8.0 or so earthquake struck along the Fairweather Fault, its epicenter just 13 miles (21 km) from Lityua Bay in Alaska. The earthquake caused a large landslide in the bay — located within Glacier Bay National Park — which triggered one of the largest tsunamis ever recorded in modern times. Waves reached a height of 1,720 feet (576 meters) in the bay, but because the area is relatively isolated and in a unique geologic setting, the tsunami did not cause much damage elsewhere. It sank a single boat, killing two fishermen.

(Shown here, an aerial image showing the bay just weeks after the tsunami.)

The 2004 Indian Ocean Tsunami

On Dec. 26, 2004, a colossal earthquake with a magnitude between 9.1 and 9.3 shook Indonesia and killed an estimated 230,000 people, most due to the tsunami and the lack of aid afterward, coupled with deviating and unsanitary conditions. The quake was named the Sumatra-Andaman earthquake, and the tsunami has become known as the 2004 Indian Ocean tsunami. Those waves traveled the globe — as far as Nova Scotia and Peru.

Japan Quake and Tsunami

The magnitude-9.0 earthquake that struck Japan on March 11, 2011, was the largest known quake to strike the seismically active country and the world's fourth-largest earthquake in recorded history. While the quake itself was responsible for relatively few deaths, the massive tsunami it generated rapidly inundated coastal areas and took some residents by surprise; the raging waters accounted for the bulk of the deaths in the disaster. Some 20,000 people perished or are considered missing.

As the waves of a tsunami approach a coastline, the topography of the seafloor near the coast plays a major role in determining how large those waves become and what places get hit harder than others.

For example, when the waves of the massive tsunami generated by last year's magnitude 9.0 Japan earthquake crossed the Pacific Ocean and reached the U.S. West Coast, they hit Crescent City, Calif., particularly hard because of two features of the seafloor off the coast: a piece of the ocean floor raised by tectonic activity that runs directly toward the city and the position and shape of the city's harbor.

Scientists had suspected that the same phenomenon might also take place in the deep ocean, where underwater mountains, called seamounts, chasms and even islands could deflect tsunami waves in some places and amplify them in others.

But measurements taken by satellites passing over the waves of last year's tsunami have confirmed that this happens, even at large distances from a quake's epicenter.

Researchers from NASA's Jet Propulsion Laboratory and Ohio State University used satellite altimeters, which can measure sea level changes in very fine detail, to observe "merging tsunamis" — a phenomenon where smaller waves merge to form one bigger wave. These waves can travel hundreds to thousands of miles without losing power.

The measurements showed that the March 2011 tsunami doubled in intensity when passing over rugged ocean ridges and around islands in the middle of the Pacific.

The team used a computer-based model to translate the measurements into images and animations, which shows how the waves can refract, bend and merge as they propagate. The peaks of waves are colored red-brown, while depressions in sea surface appear blue-green. Grayscale outlines show the location of mid-ocean ridges, peaks and islands.

The measurements came from the Jason-1, Jason-2, and Envisat satellites, which each flew over the tsunami at a different location.

"It was a one in 10 million chance that we were able to observe this double wave with satellites," said Tony Song, principal investigator of the study and a scientist at JPL.

"Researchers have suspected for decades that such ‘merging tsunamis’ might have been responsible for the 1960 Chilean tsunami that killed about 200 people in Japan and Hawaii, but nobody had definitively observed a merging tsunami until now. It was like looking for a ghost," Song said. "Jason happened to be in the right place at the right time to capture the double wave."

This story was provided by OurAmazingPlanet, a sister site to LiveScience.

It doesn't sound like much, but just a few seconds of warning time could be helpful during an earthquake.

That is especially true in the United States, which may not be as prepared for a major quake as Japan, where a magnitude 9.0 earthquake and tsunami struck one year ago this weekend, killing more than 20,000 people. A future earthquake warning system in California, still years away for the public, could someday provide those precious few seconds to alert people that a quake is coming. Data from the Japan earthquake is helping test the system.

The plan is that a network of seismometers will detect the waves of an earthquake before those waves arrive in a big city. Information about the quake could then be beamed to people in the city in the few seconds before the ground begins to shake, said geophysicist Victor Tsai, of Caltech, who is working on the early warning system. The warnings could remove the "are we or aren't we having an earthquake?" confusion.

"Say you have five to 10 seconds of warning, maybe you could prepare yourself much better," Tsai said. "You could hide under your desk more easily."

The warning system could block the sucker-punch that earthquakes often deliver to a city's infrastructure. Early warnings would allow utilities to shut off the gas. Buildings could open their elevator doors so no one is trapped. Even trains could take detours to avoid riding into an impending disaster.

Early stages

Scientists in California are still in early stages of developing the techniques and framework for their warning system. Data from the Japan quake, considered the best-documented quake of all time, is helping the scientists test their warning algorithms.

A skeleton network is in place today in California. Whenever a quake strikes, some 100 researchers get an early warning. California's transit agency also gets these preliminary early warnings. The magnitudes aren't always correct, but trained operators can plot the quake on a map and highlight problem areas, such as bridges or tunnels that could be damaged.

The system won't be ready for the public until it is more precise and better able to filter out false alarms, Tsai told OurAmazingPlanet.

Warnings later, better education today

Until that far-off day when the system is texting or tweeting earthquake warnings, better education could help save lives today, Tsai said.

"One of the main issues is that if people were better educated about what they should do in an earthquake, it would better save lives," Tsai said.

In the Japan quake, the shaking was very long — up to 400 seconds. If more people were very well educated, then they would have known that such a large amount of shaking could come only from a very large quake, possibly even a notorious subduction zone earthquake, which are known to trigger massive tsunamis. With that knowledge, more people could have fled inland to higher ground.

"That would have saved lives," Tsai said. "A lot of people don't know these things."

You can follow OurAmazingPlanet staff writer Brett Israel on Twitter: @btisrael. Follow OurAmazingPlanet for the latest in Earth science and exploration news on Twitter @OAPlanet and on Facebook.

A new analysis of the March 11, 2011, tsunami that devastated Japan's east coast could improve flooding forecasts and help prevent a similar disaster from occurring in the future.

Despite an extraordinary level of preparedness by the Japanese, the massive tsunamithat followed the magnitude 9.0 earthquakecaused more than 90 percent of the almost 20,000 fatalities from the disaster.

Using eyewitness video and laser scanners from atop the highest buildings that surveyed the tsunami, a team of researchers has mapped the tsunami's height and flood zone to learn more about the flow of the devastating currents.

The work could improve tsunami warnings by producing flooding forecasts that influence future evacuation plans and building designs in Japan and in other areas of the world susceptible to tsunamis, according to the study team.

"The ultimate goal is to save lives," said study team member Hermann Fritz of Georgia Tech. "In order to do so, we have to have a better understanding of what worked and didn't work."

Fritz led a reconnaissance team surveying the impact of the tsunami on a fishing town in Kesennuma Bay, where 1,500 people perished. The bay has been hit by tsunamis in 1896, 1933, 1960 and 2010. The coastal structures and other mitigation measures on the coast were designed based on conservative, historic high-water marks, rather than probable maximum tsunamis. [Pictures: Japan Earthquake & Tsunami]

From atop buildings where witnesses gathered during the tsunami, Fritz and his team used lasers to scan the port and bay entrance, creating a three-dimensional, topographic model — called a hydrograph — of the flood zone.

Using this data, they reconstructed eyewitness videos to determine the heights and flow of the tsunami. They determined that the tsunami reached a maximum height of 29.5 feet (9 meters), followed by outflow currents of 36 feet per second (11 meters per second) less than 10 minutes after the main peak hit — a speed which Fritz says is impossible to survive or navigate by vessels.

"What we can learn from the hydrograph is confirmation that the water goes out first, drawing down to more than negative 3 meters [10 feet] on the landward side of the trench, which can make vessels hit ground inside harbors," Fritz said. "During the subsequent arrival of the main tsunami wave, the water rushing back in changed the water level by 40 feet [12 m], engulfing the entire city in 12 minutes."

Understanding tsunami impacts will help prepare for future disasters — whether it's designing buildings high enough to serve as vertical evacuation points or sea walls and breakwaters strong enough to control the flow of water.

Follow OurAmazingPlanet for the latest in Earth science and exploration news on Twitter @OAPlanet and on Facebook.

A new animation shows the path of the debris carried out to sea by last year's massive tsunami in Japan.

The tsunami triggered by the devastating earthquake that struck off the east coast of Japan on March 11, 2011,produced an estimated 25 million tons of debris. Much of this debris was swept out into the Pacific Ocean as the waters retreated.

The new animation shows its probable path, which is helpful to shipping traffic since some of the debris is dangerously large. Debris-tracking missions have already found two fishing vessels that were carried out to sea by the tsunami.

Where it's heading

Since that magnitude 9.0 quake, the debris that has stayed afloat has drifted apart due to winds and ocean currents, with most of it moving eastward. Scientists have predicted the debris could wash up along the West Coast of the United States by next year.It is expected to hit Midway Atoll this winter and the main Hawaiian Islands in the winter of 2012-2013.

All is clear at the Midway Atoll so far this winter, though. The ocean currents have kept any debris away, said Jan Hafner of the International Pacific Research Center, who is part of the team that modeled the debris path.

"The currents are changing constantly and we expect the tsunami debris to reach there soon," Hafner told OurAmazingPlanet.

The debris has dispersed and is not visible by satellites, so scientists deployed hundreds of high-tech devices to help monitor the path of the debris, which could be hazardous to ships, marine life and coastlines.

Identifying debris A few big pieces of debris have turned up. At the end of September 2011, a Russian ship reported the edge of the debris field 250 miles (400 kilometers) northwest of Midway. About 100 miles (161 km) farther on, the ship found a 20-foot-long (6 meters) boat from Fukushima, which was identified by its markings.

Along the West Coast of North America, news reports have suggested that debris is already arriving. Debris from Asia, however, routinely washes up here, so scientists are cautious before confirming any debris they find is from the tsunami.

"If an unusually large amount of unusual types of debris washes on a beach, that is an indication of debris from the tsunami," Hafner said.

Scientists also look for identifying markers, such as registration numbers, Hafner said.

One of the fishing vessels had markings on the wheelhouse of the boat that showed its homeport to be in Fukushima Prefecture, the area hardest hit by the massive tsunami.

The U.S. National Oceanic and Atmospheric Administration (NOAA) has urged anyone that spots potential tsunami debris to report it by emailing DisasterDebris@noaa.gov.

You can follow OurAmazingPlanet staff writer Brett Israel on Twitter: @btisrael. Follow OurAmazingPlanet for the latest in Earth science and exploration news on Twitter @OAPlanet and on Facebook.

VANCOUVER, British Columbia — In 2011, Japan was one of the most prepared countries in the world for a massive earthquake. Yet when a mega-quake hit Japan last March, sparking a huge tsunami, it was shockingly devastating.

Now, almost a year after the Japan earthquake, scientists say the hard lessons learned will go a long way toward being better prepared next time.

"It was very large and largely unanticipated by many seismologists," James Mori of Kyoto University's Disaster Prevention Research Institute said here Sunday (Feb. 19) at the annual meeting of the American Association for the Advancement of Science. "It was actually very disheartening for all the people doing earthquake research and hazard mitigation in Japan."

The quake, a whopping 9.0 on the magnitude scale used to rate the severity of earthquakes, struck off the east coast of Japan's Tohoku region on March 11. The temblor, the strongest ever to hit Japan and among the five most powerful earthquakes ever recorded, caused a massive tsunami wave that reached heights up to 133 feet (40.5 meters).

More than 22,000 people were reported dead or missing.

"The fact that tens of thousands of people were killed was really a shock," Mori said. "I think people thought that such kinds of events wouldn't happen in Japan with all the work put into earthquake research and hazard mitigation."

Lessons learned

Part of the reason scientists weren't expecting such a strong quake in Japan was the fact that a quake that powerful had never before been recorded, and seismic predictions based on the known record of earthquakes in Japan did not forecast such an event.

"The lesson is that 400 or 500 years of historical records is not enough," Mori said.

In the wake of the Tohoku quake, researchers hope to make significant improvements to earthquake models and forecasting, both for Japan, and for the entire planet. They have a wealth of data to work from, as no other large earthquake in history has been recorded by as many instruments with as much precision, said John Anderson, a seismologist atthe University of Nevada.

"At last we have a very well-recorded mega earthquake, and the data is extraordinary," Anderson said.

For example, the data reveal that the ground motions were actually less violent than might have been predicted for such a huge earthquake. Between that fact, and the high building standards in Japan that ensured many structures were designed to withstand strong quakes, the property damage and loss of life from the earthquake alone were not as significant as they could have been.

"The shaking itself was not responsible for a large fraction of deaths — it was mostly the tsunami," Anderson said.

Disaster response

In addition to shedding light on the science of earthquakes, the experience of Japan is shaping ideas of how best to respond to disasters.

While Japan has in place a high-tech warning system to alert the public when an earthquake is imminent, it didn't work as well as it might have last March.

The warning was issued just eight seconds after the first wave of the earthquake was detected, Mori said. It sent a message to 124 television stations and 52 million phones. It automatically caused bullet trains to stop and elevators to halt.

However, calculations of the earthquake's likely strength based on the initial wave turned out to be wrong because the earthquake increased in power over time. Consequently, the system underestimated the severity and extent of the temblor, and the warning was not sent to places like Tokyo, which initially seemed too far to be affected, but actually was.

"That's just one of the inherent problems of the system and something that has to be dealt with," Mori said.

Furthermore, the tsunami warning, which followed the earthquake warning, did not reach many coastal residents who had already evacuated, or whose televisions and radios had stopped working due to power outages sparked by the earthquake.

Despite the fact that the tsunami hit 30 to 60 minutes later than the earthquake, many people had no warning of this more dire threat. [History's Biggest Tsunamis]

In the future, better alert systems are needed to send out updated information to the public before and during an emergency, the experts said.

This story was provided by OurAmazingPlanet, a sister site to LiveScience. You can follow senior writer Clara Moskowitz on Twitter @ClaraMoskowitz. Follow OurAmazingPlanet for the latest in Earth science and exploration news on Twitter @OAPlanet and on Facebook.

The tsunami triggered by last year's devastating earthquake in Japan produced an estimated 25 million tons of debris. Much of this debris was swept into the Pacific Ocean. Where it will go is what scientists want to know.

Since that magnitude 9.0 quake, the debris that has stayed afloat has drifted apart due to winds and ocean currents, with most of it moving eastward. Scientists predicted the debris could wash up along the West Coast of the United States by next year and Hawaii perhaps as soon as this winter. But the makeup of the debris and how much is still floating on the surface are largely unknown.

Scientists have now deployed hundreds of high-tech devices to help monitor the path of the debris, which could be hazardous to ships, marine life and coastlines.

Buoys in place

To track where this debris is headed, a team of scientists and conservationists from the University of Hawaii at Manoa and at Hilo, the Scripps Institution of Oceanography, and the Ocean Recovery Alliance has surveyed the debris field and marked it with satellite-tracked drifting buoys, designed to simulate the motion of different types of debris. This drifter array, deployed in a line between Midway Atoll and the leading edge of the tsunami debris field, can now monitor the debris' movement remotely and provide warnings. [History's Biggest Tsunamis]

At the end of November 2011, the team launched an expedition from Honolulu to Midway Atoll and beyond. The team relied on the projections of a computer model to guide their debris search. The model, based on the trajectories of historical drifters, predicted that the debris was heading toward Midway and Papahanaumokuakea Marine National Monument, arriving there as early as this winter.

The model's trajectory had been confirmed at the end of September 2011 by the Russian ship Pallada, which reported the edge of the debris field 250 miles (400 kilometers) northwest of Midway. About 100 miles (161 km) farther on, the ship found a 20-foot (6-meter) boat from Fukushima.

Avoiding the atolls

The debris survey team also deployed 400 numbered wooden blocks along the route, often near floating debris. If boaters, fishermen and beachgoers find these blocks and contact the scientists by the information on the blocks, they will help the debris trackers' understanding of the motion of debris and currents in this remote region.

So far, the team has found that the Japan tsunami debris has recently not advanced toward Midway, but instead has been flowing eastward well to the north of the atolls. Analysis of the ocean currents shows that for the past weeks, the general flow around the Hawaiian Islands has been from the southwest, producing a front 300 miles to 400 miles (483 to 644 km) northwest of Midway that has kept the debris north of the islands.

Although this flow has prevented tsunami debris from approaching the islands, it carries a lot of trash from the Pacific Garbage Patch between Hawaii and California. The expedition documented 175 pieces of ordinary debris. The team photographed and collected many of the pieces for more thorough laboratory examination. Radiation testing on these pieces of debris, and the surrounding water, has not revealed any significant radiation.

Follow OurAmazingPlanet for the latest in Earth science and exploration news on Twitter @OAPlanet and on Facebook.

This much is known: The devastating earthquake and tsunami that hit Japan on March 11 created a massive amount of debris, some of which was washed back into the ocean as the waters retreated. Prevailing currents are carrying that debris toward the United States.

But when and where — if ever — it will wash ashore is still in question, and scientists are still tracking how much is floating toward the West Coast.

The magnitude-9.0 quake and tsunami — the costliest disaster of all time — were so powerful that they broke off huge icebergs thousands of miles away in the Antarctic, locally altered Earth's gravity field and washed millions of tons of debris into the Pacific. The Japanese government estimated that the tsunami generated 25 million tons of rubble, but no one is sure how much of that washed into the ocean, or whether any debris stayed afloat.

"It's difficult to say exactly how much debris is expected to show up, and when and where," said Dianna Parker, a spokeswoman with the NOAA Marine Debris Program.

Not much to see

Not helping the trackers is that they can no longer see the piles of debris by satellite. Winds and ocean currents scattered items in the massive North Pacific Ocean.

Since trackers cannot rely on satellites, they are using computer models to guess where the debris will go. NOAA's model estimates that debris could show up in Hawaii as early as this winter. The West Coast could see debris in 2013, and the debris could circle back to Hawaii some time between 2014 and 2016, Parker told OurAmazingPlanet.

But there are many limitations to the forecast; debris could sink or break up and disperse in the ocean.

"We're preparing for high amounts of debris, but we're also preparing for little to nothing," Parker said.

Another problem is distinguishing debris from the quake from trash floating in the ocean from other sources. Two fishing vessels found in the middle of the Pacific Ocean are the only pieces of debris traveling across the ocean that have been directly linked to the tsunami.

To confirm that debris is from Japan, scientists look for identifying markers or serial numbers. Researchers aboard a Russian ship, the STS Pallada, spotted a number of floating items, including a TV set, refrigerator and one of the two fishing ships. The small fishing vessel, about 20 feet (6 meters) long, had markings on the wheelhouse of the boat that showed its homeport to be in Fukushima Prefecture, the area hardest hit by the massive tsunami.

Early reports

Already, communities on the coast of British Columbia, Canada, have reported debris that appears to be from Asia, including plastic bottles and lumber. NOAA hasn't yet ruled on if this debris is from the tsunami.

"Debris from Asia washes up on the West Coast all the time," Parker said. "That's typical of the kinds of things that wash ashore."

The trash reported in Canada is small, but the tracking effort could curtail damage from a big piece of debris, such as a ship, hitting a coast or coral reef. Removing any large debris could be expensive, and it's not clear where all the money would come from to pay for cleanup and removal. NOAA expects to have funds available to help, Parker said.

None of the debris is thought to be radioactive, since it washed into the ocean before the nuclear disaster at the crippled Fukushima power plant. Still, NOAA is urging caution around the debris.

"We encourage people not to touch items that they think are hazardous," Parker said. Debris can be reported by emailing DisasterDebris@noaa.gov.

You can follow OurAmazingPlanet staff writer Brett Israel on Twitter: @btisrael. Follow OurAmazingPlanet for the latest in Earth science and exploration news on Twitter @OAPlanet and on Facebook.

Science 2011

From the last space shuttle mission and spotting Earth-size planets orbiting another star to the possible detection of the elusive Higgs boson particle and some extreme (and very costly) weather, 2011 was filled with science, albeit sometimes disastrous. Here are 11 of the most compelling and significant science stories to break this year.

Tough Times

The U.S. may have exited the recession this year, but the amount of time Americans go without work has reached a record level. And psychologists say this doesn't bode well for our emotional health. Census data also shows increases in the nation's poverty rate in recent years. Americans feel their financial situation was getting worse, not better, and even their pets are suffering. The Great Recession of 2007 to 2009 hit all children hard, but seems to have caused the largest increase in childhood poverty among Latino kids.

Killer Contaminated Cantaloupes

An outbreak of listeriosis, an infection caused by the bacterium Listeria monocytogenes, spread by contaminated cantaloupes infected 146 people and killed 30 this fall, the U.S. Centers for Disease Control and Prevention reported in December. Health officials recommend washing melons particularly cantaloupes before slicing them to remove any bacteria clinging to the rind.

The Last Space Shuttle

Thirty years after launching its first space shuttle, Columbia, NASA ended its space shuttle program in July with a final mission by the shuttle Atlantis. NASA has no immediate plans to replace the shuttles, but is instead focusing on manned voyages beyond low orbit, such as to the moon and Mars. In the immediate future, a combination of commercial ventures, whose craft are still being developed, and other nation's craft, such as the Russian Soyuz and Progress, are expected to take over the task of ferrying American astronauts and experiments back and forth to the International Space Station (ISS).

Mutant Flu Virus Created in Lab

Bird flu, also known as H5N1, rarely infects people, but when it does the results are often deadly: Of the 600 cases reported since 2003, about 60 percent have been fatal. To better understand how the virus might change into a form that could easily spread between people, two groups of scientists altered the virus in their labs, creating the sort of pathogen that could start a pandemic.

Biosecurity officials have called for crucial details of their work to be kept under wraps — to prevent it from falling into the wrong hands — and some have questioned whether the work should have been done at all.

Japan's Earthquake, Tsunami & Nuclear Crisis

On March 11, an earthquake, measuring a magnitude of 8.9, struck off the coast of Japan. The earthquake was the most powerful to ever hit the country, and it was followed by the walls of water – caused by the subsequent tsunamis – which wreaked havoc. These disasters set off the worst nuclear emergency since Chernobyl when massive amounts of radiation were released from nuclear power plants. Reactors at the Fukushima nuclear power plant melted down, and the surrounding area evacuated.

Alarming Firsts in the Arctic

The ozone hole over the Antarctic is nothing new, although scientists expect it to disappear later this century. But this year, an Arctic counterpart emerged for the first time, thanks to unusually cold temperatures in the stratosphere plus lingering ozone-destroying pollutants. Arctic sea ice also melted — either to its lowest summer extent on record, or its second lowest, depending on who did the measuring.

Exceeding the Speed of Light?

Reports that physicists had accelerated subatomic particles, called neutrinos, faster than the speed of light appeared to upset modern physics and even the nature of causality. Einstein's Theory of Special Relativity gives a special status to the speed of light as a cosmic speed limit. Anything exceeding the speed of light would travel backwards time, interfering with the basic rule that cause precedes effect, called causality. However, this all may have been a false alarm. More recent evidence indicates the neurtrinos never traveled that quickly, though the jury is still out.

Planets Like Ours

Astronomers came a step closer to locating a habitable, Earth-like planet, when they found two, roughly Earth-sized planets orbiting a star 950 light-years away. These are the smallest, most Earth-size alien worlds known. Their close proximity to their sun means they are too hot to be habitable, however.

Our Ancestors' Secrets

It seems our ancestors not only mated with Neanderthals, they also got it on with another, even more mysterious archaic hominin species. Called the Denisovans, these people lived about 40,000 years ago and are known to us only from a few bone fragments and teeth. Research has uncovered Denisovan genes in modern East Asian and Pacific Island populations.

Closing in on the Higgs Particle

Physicists say they are closing in on an elusive subatomic particle, called the Higgs boson, that could confirm their theory on where mass comes from. The Higgs boson is thought to be tied to a field (the Higgs field), which is responsible for giving all other particles their mass.

Disastrous Weather & Climate Change

Drought, wildfire, tornadoes, flooding, a blizzard and a hurricane — weather-related disasters wreaked havoc on the United States in 2011, setting a new record for costly weather-related disasters. In December, the National Oceanic and Atmospheric Administration (NOAA) announced the country had experienced 12 $1 billion-plus of them. And we can expect more, said NOAA head Jane Lubchenco, citing predictions of more severe weather brought by climate change. Americans seem to be getting the message; an annual survey found we are starting to see climate change as an immediate problem, thanks to this year's devastating weather.

The massive tsunami generated by the March 2011 earthquake off the coast of northeastern Japan was a "merging tsunami" — a type of tsunami long thought to exist, but seen now for the first time, scientists report.

The magnitude-9.0 Tohoku-Oki temblor, the fifth-most powerful quake ever recorded, triggered a tsunami that doubled in intensity over rugged ocean ridges, amplifying its destructive power at landfall, as seen in data from NASA and European radar satellites that captured at least two wave fronts that day. The fronts merged to form a single, double-high wave far out at sea. This wave was capable of traveling long distances without losing power. Ocean ridges and undersea mountain chains pushed the waves together along certain directions from the tsunami's origin.

The discovery, presented today (Dec. 5) at the annual meeting of the American Geophysical Union in San Francisco, helps explain how tsunamis can cross ocean basins to cause massive destruction at some locations while leaving others unscathed. The data raise hope that scientists may be able to improve tsunami forecasts.

"It was a one-in-10-million chance that we were able to observe this double wave with satellites," said study team member Y. Tony Song, of NASA's Jet Propulsion Laboratory in Pasadena, Calif., who presented with team member C.K. Shum of The Ohio State University.

Right place, right time "Researchers have suspected for decades that such 'merging tsunamis' might have been responsible for the 1960 Chilean tsunami that killed about 200 people in Japan and Hawaii, but nobody had definitively observed a merging tsunami until now,” Song said in a statement. "It was like looking for a ghost. A NASA-French Space Agency satellite altimeter happened to be in the right place at the right time to capture the double wave and verify its existence." The NASA-Centre National d'Etudes Spaciales Jason-1 satellite passed over the tsunami on March 11, as did two other satellites — the NASA-European Jason-2 and the European Space Agency's EnviSAT. All three carry radar altimeters, which measure sea-level changes to an accuracy of a few centimeters. Each satellite crossed the tsunami at a different location, measuring the wave fronts as they occurred. [Video: Japan Tsunami's Effects] The researchers think ridges and undersea mountain chains on the ocean floor deflected parts of the initial tsunami wave away from each other to form independent jets shooting off in different directions, each with its own wave front.

Better risk maps The sea floor topography nudges tsunami waves in varying directions and can make its destruction appear random. For that reason, hazard maps that try to predict where tsunamis will strike rely on sub-sea topography. Previously, these maps considered only topography near a particular shoreline. This study suggests scientists may be able to create maps that take into account all undersea topography, even sub-sea ridges and mountains far from shore.

"We can use what we learned to make better forecasts of tsunami danger in specific coastal regions anywhere in the world, depending on the location and the mechanism of an undersea quake," Shum said. Song and his team were able to verify the satellite data through model simulations based on independent data, including GPS data from Japan and buoy data from the National Oceanic and Atmospheric Administration's Deep-Ocean Assessment and Reporting of Tsunamis program. "Tools based on this research could help officials forecast the potential for tsunami jets to merge," Song said. "This, in turn, could lead to more-accurate coastal tsunami-hazard maps to protect communities and critical infrastructure."

Follow OurAmazingPlanet for the latest in Earth science and exploration news on Twitter @OAPlanet and on Facebook.

SAN FRANCISCO — The devastating tsunami that struck Japan after the massive Tohoku earthquake March 11 appears to have generated misperceptions about tsunami dangers among Japanese citizens.

Surveys conducted a year before the March tsunami and then afterward reveal a potentially deadly shift in perception among citizens in western Japan, Satoko Oki, an assistant professor at the Earthquake Research Institute, University of Tokyo, said here today (Dec. 5) at the annual meeting of the American Geophysical Union.

The tsunami that struck the coastof Japan March 11 hit roughly 30 minutes after the magnitude-9.0 Tohoku earthquake. The waves were reported to reach three stories high. The disaster is estimated to have killed approximately 20,000 people.

When participants in the online, representative survey were asked, 'What height of a tsunami would you consider dangerous?' in March 2010, 70.8 percent of respondents said that less-than-10 feet (3 meters) was dangerous.

This was the correct answer, according to Oki.

"A 2-meter-high [7-foot] tsunami can completely destroy your house," she said.

But in the later survey, conducted in April 2011, fewer — 45.7 percent — of survey respondents responded correctly.

Likewise, when asked, 'At what estimated height of tsunami would you evacuate?' 60.9 percent said less-than-3 meters (10 feet). A year later, 38.3 percent agreed with this.

"So the damage lowered the risk assessment, it did not teach a lesson, but instead, it made the Japanese people more vulnerable than before," Oki said.

She then showed headlines reporting tsunami waves measuring from 49 feet (15 meters) to the near-record 124 feet (37.9 meters) hitting the coast of Japan.

After March 11, Japanese kept hearing those numbers over and over again, and they began to evaluate the danger associated with tsunamis against those numbers, she said. So, a smaller height began to seem less dangerous, even if it wasn't.

To prevent this from happening in the future, Oki recommended that information available to the public should make clear the risk associated with relatively small tsunamis, including it in reports describing tsunamis like the one in March.

Japanese officials are considering not including projected tsunami heights with future evacuation orders, she said.

This story was provided by OurAmazingPlanet, a sister site to LiveScience. You can follow LiveScience senior writer Wynne Parry on Twitter @Wynne_Parry. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

Three-dimensional animations of the devastating earthquake that rocked Japan this year are now helping visualize the effects of its motions.

These animations could help the public better understand such temblors, researchers said.

The magnitude 9.0 quake that struck off the coast of Tohoku in Japan in March ushered in what might be the world's first complex megadisaster as it unleashed a catastrophic tsunami, nuclear crisis and set off microquakes and tremors around the globe.

Scientists analyzed 3-D position data from a dense web of more than 1,200 GPS receiver stations on the ground in Japan to get a clearer picture of the shaking. [See video of the quake animation.]

"When the massive data set from Japan became available through the ARIA project of JPL-Caltech, I had to come up with a better way to look at all this information," said geophysicist Ronni Grapenthin at the University of Alaska at Fairbanks.

Slipping and sinking

The researchers have now developed animations of the quake's effects. Altogether, the vertical and horizontal motions pulled parts of the nation more than 13 feet (4 meters) to the east and sank large portions of its eastern shore more than 1.6 feet (0.5 meters) into the sea.

"Looking at the record of all instruments simultaneously allows us to watch the evolution of this earthquake," Grapenthin told OurAmazingPlanet.

The researchers suggest their animations can help people understand the quake's effects more intuitively than standard methods, such as peaks on a seismograph or maps overlain with the locations and magnitudes of temblors.

"When you see a good portion of Japan slide into the sea, you intuitively know those arrows represent a major disaster," Grapenthin said.

The scientists added that automated methods of animating real-time data from GPS stations could be useful in properly gauging the severity of quakes. For instance, "the initial estimates of the size of the main shock [of the Tohoku earthquake] was magnitude 7.9," Grapenthin said. "Near real-time visualization of the GPS record in map view would have made clear that this is a gross underestimate, as a large portion of central Japan slid to the east."

Improving tsunami warnings

Such animations could also prove helpful in early warning systems for tsunamis and aftershocks. For instance, by seeing the estimated length of a ruptured fault, investigators can identify areas prone to large aftershocks. Also, knowing that large portions of Japan's eastern shore had sunken would have revealed that protective levees were now much lower than expected, giving rapid insight into a potential tsunami and its effects.

"Since the data is already in map view, we know exactly where these exposed regions are," Grapenthin said. "This would require an extension of the network of continuous GPS stations that transmit their data in real-time and wider availability of GPS data processing in real-time."

However, establishing such an effort in the United States wouldn't be easy.

"Funding the installation and maintenance of a dense continuous GPS network is an issue — except for regions in the Pacific Northwest and California, the U.S. comes nowhere near the GPS station density of Japan," Grapenthin cautioned. "There are places like Alaska that produced giant earthquakes with big tsunamis in the recent past and have the potential to do so again, yet the instrumentation along the Aleutian Trench is rather sparse." The Aleutian Trench is a subduction zone that runs along the southern coastline of Alaska.

Grapenthin and his colleague Jeffrey Freymueller detailed their findings online Sept. 22 in the journal Geophysical Research Letters.

This story was provided by OurAmazingPlanet, a sister site to LiveScience.

Debris from the devastating tsunami that hit Japan on March 11 has turned up exactly where scientists predicted it would after months of floating across the Pacific Ocean. Finding and confirming where the debris ended up gives them a better idea of where it's headed next.

The magnitude 9.0 quake and ensuing tsunami that struck off the coast of Tohoku in Japanwas so powerful that it broke off huge icebergs thousands of miles away in the Antarctic, locally altered Earth's gravity field, and washed millions of tons of debris into the Pacific.

Scientists at the International Pacific Research Center at the University of Hawaii at Manoa have been trying to track the trajectory of this debris, which can threaten small ships and coastlines. The new sightings should help the scientists predict when the debris, which ranges from pieces of fishing vessels to TV sets, will arrive at sensitive locations, such as marine reserves. (Scientists estimate the debris will wash up on the Hawaii Islands in two years and the U.S. West Coast in three.)

Debris sighted

For nearly half a year, senior researcher Nikolai Maximenko and computer programmer Jan Hafner had only their state-of-the-art — but still untested — computer model of ocean currents to speculate where the tsunami debris might end up . The new sightings are backing up the model, showing debris in places where the model predicted.

Warned by maps of the scientists' model, a Russian ship, the STS Pallada, found an array of unmistakable tsunami debris on its homeward voyage from Honolulu to Vladivostok.

Soon after passing Midway Islands, crew members aboard the Pallada spotted a surprising number of floating items.

"Yesterday, i.e. on September 22, in position 31 [degrees] 42,21 N and 174 [degrees] 45,21 E, we picked up on board the Japanese fishing boat. Radioactivity level — normal, we've measured it with the Geiger counter," wrote Natalia Borodina, information and education mate of the Pallada. "At the approaches to the mentioned position (maybe 10 – 15 minutes before) we also sighted a TV set, fridge and a couple of other home appliances."

Later, on Sept. 27, she wrote: "We keep sighting every day things like wooden boards, plastic bottles, buoys from fishing nets (small and big ones), an object resembling wash basin, drums, boots, other wastes. All these objects are floating by the ship."

A map shows the stretch of Pallada's route where debris was sighted between Sept. 21 and 28. The red rhombus marks the location where the Japanese boat was found and the red circle denotes where maximum debris density was experienced.

The purple color shows the distribution of the tsunami debris in the SCUD model on Sept. 25.

Where debris hits next

On Oct. 8, the Pallada entered the port of Vladivostok and Borodina was able to send pictures.

The most remarkable piece of debris is of a small fishing vessel about 20 feet (6 meters)long, which they were able to hoist up onto the Pallada. The markings on the wheelhouse of the boat show its homeport to be in the Fukushima Prefecture, the area hardest hit by the massive tsunami.

With the exact locations of some of the now widely scattered debris, the scientists can make more accurate projections about when the debris might arrive at the Papahanaumokuakea Marine National Monument. The first landfall on Midway Islands is anticipated this winter. What misses Midway will continue toward the main Hawaiian Islands, where it is expected to hit in two years, and then on to the West Coast of North America in three years.

Follow OurAmazingPlanet for the latest in Earth science and exploration news on Twitter @OAPlanet and on Facebook

The devastating earthquake that struck Japan this year may have rattled the highest layer of the atmosphere even before it shook the Earth, a discovery that one day could be used to provide warnings of giant quakes, scientists find.

The magnitude 9.0 quake that struck off the coast of Tohoku in Japan in March ushered in what might be the world's first complex megadisaster as it unleashed a catastrophic tsunami and set off microquakes and tremors around the globe.

Scientists recently found the surface motions and tsunamis this earthquake generated also triggered waves in the sky. These waves reached all the way to the ionosphere, one of the highest layers of the Earth's atmosphere.

Now geodesist and geophysicist Kosuke Heki at Hokkaido University in Japan reports the Tohoku quake also may have generated ripples in the ionosphere before the quake struck.

Disruptions of the electrically charged particles in the ionosphere lead to anomalies in radio signals between global positioning system satellites and ground receivers, data that scientists can measure.

Heki analyzed data from more than 1,000 GPS receivers in Japan. He discovered a rise of approximately 8 percent in the total electron content in the ionosphere above the area hit by the earthquake about 40 minutes before the temblor. This increase was greatest about the epicenter and diminished with distance away from it.

"Before finding this phenomenon, I did not think earthquakes could be predicted at all," Heki told OurAmazingPlanet. "Now I think large earthquakes are predictable."

Analysis of GPS records from the magnitude 8.8 Chile earthquake in 2010 revealed a similar pattern, Heki said. These anomalies also may have occurred with the Sumatra magnitude 9.2 earthquake in 2004 and the magnitude 8.3 Hokkaido earthquake in 1994, he added.

If true, further research could lead to a new type of early-warning system for giant earthquakes.

The anomaly is currently seen before earthquakes only with magnitudes of about 8.5 or larger, Heki cautioned. Still, if researchers can detect what specifically causes this ionospheric phenomenon, it also might be possible to detect precursory phenomena for smaller earthquakes, he said.

Heki did caution that the ionosphere is highly variable — for instance, solar storms can trigger large changes in total electron content there. Before researchers could develop an early-warning system for earthquakes based on ionospheric anomalies, they would have to rule out non-earthquake causes.

Heki detailed his findings online Sept. 15 in the journal Geophysical Research Letters.

This story was provided by OurAmazingPlanet, sister site to LiveScience.

A flurry of recent earthquakes has rumbled in the Pacific, but they are normal for the region and not related to each other, according to the U.S. Geological Survey (USGS).

A magnitude 7.3 earthquake struck deep underground near Fiji today (Sept. 15). A magnitude 6.2 quake also struck off the coast of the Japanese island of Honshu, where earlier this year a massive magnitude 9.0 quake devastated the country . New Zealand saw a 6.0 quake off its North Island today. Yesterday a 6.1 magnitude quake struck Alaska's Aleutian Islands, and last week a magnitude 6.4 quake struck near Vancouver Island, with shaking felt as far away as Seattle, Wash.

The quakes were all in the same seismic area, but other than that, they are unrelated, said geophysicist John Bellini of the USGS. The quakes all struck in the seismically and volcanically active Pacific Ring of Fire , but they were not triggered by each other.

"When things like that happen [one quake triggering another], it's usually immediately after," Bellini told OurAmazingPlanet.

For example, when a large earthquake hits in the Gulf of California, it's common for quakes to immediately follow in Yellowstone, Bellini said.

A magnitude 7.3 is typical for the region near Fiji, and the quake was much too deep 389 miles (626 kilometers) below the Earth's surface to trigger a tsunami, Bellini said.

• 7 Most Dangerous Places on Earth
• Image Gallery: This Millennium's Destructive Earthquakes
• The 10 Biggest Earthquakes in History

7 Most Dangerous Places on Earth

You can follow OurAmazingPlanet staff writer Brett Israel on Twitter: @btisrael. Follow OurAmazingPlanet for the latest in Earth science and exploration news on Twitter @OAPlanet and on Facebook.

Scientists in California got an early look at the tsunami generated by the massive earthquake in Japan as it rippled across the Pacific Ocean.

The March 11 Japan tsunami was picked up by high-frequency radar in California and Japan as it swept toward their coasts, according to U.S. and Japanese scientists. This is the first time a tsunami has been observed by radar, raising the possibility of new early warning systems.

"It could be really useful in areas such as southeast Asia where there are huge areas of shallow continental shelf," said John Largier, an oceanographer and study team member from the University of California, Davis. The continental shelf is the perimeter of a continent that is underwater and gradually descends to the ocean floor.

Largier and his colleagues have been using a high-frequency radar array at their lab to study ocean currents for the last 10 years. Together with collaborators from Hokkaido and Kyoto universities in Japan and San Francisco State University, the researchers used data from radar sites at Bodega Bay and Trinidad, Calif., and two sites in Hokkaido, Japan, to look for the tsunami offshore.

The radar detection is the latest in the string of new ways the Japan earthquake and tsunami were observed.Satellite images found that the tsunami was so powerful that it broke off huge icebergs thousands of miles away in the Antarctic. Scientists also found that the earthquake rattled the planet's upper atmosphere.

In the new study, scientists noticed that the radar picks up not the actual tsunami wave — which is small in height while out at sea — but changes in currents as the wave passes.

The researchers found they could see the Japan tsunamionce it entered shallower coastal waters over the continental shelf. As the waves enter the shallower water, they slow down, increase in height and decrease in wavelength until finally hitting the coast.

The continental shelf off California is quite narrow, and approaches to the coast are already well-monitored by pressure gauges, Largier said. But he said radar detection could be useful, for example, on the East Coast or in Southeast Asia, where there are wide expanses of shallow seas.

The study was published in the August edition of the journal Remote Sensing.

• Image Gallery: This Millennium's Destructive Earthquakes
• 7 Ways the Earth Changes in the Blink of an Eye
• The 10 Biggest Earthquakes in History

The giant earthquake that struck Japan this year not only shook the Earth, but also rattled the highest layer of the atmosphere, scientists find.

This research could lead to a new type of early warning system for devastating tsunamis and earthquakes.

The magnitude 9 quake that struck off the coast of Tohoku in Japan in March unleashed a catastrophic tsunami, ushered in what might be the world's first complex megadisaster and set off microquakes and tremors around the globe.

Past research revealed the surface motions and tsunamis that earthquakes generate can also trigger waves in the atmosphere. These waves can reach all the way to the ionosphere, one of the highest layers of the atmosphere.

Now scientists report the Tohoku quake generated the largest such disturbances seen yet, creating ripples in electrically charged particles reaching nearly 220 miles (350 kilometers) above the Earth.

Investigators measured these disruptions, called seismotraveling ionospheric disturbances, using about 1,000 global positioning system (GPS) receivers in Japan and Taiwan. Disruptions of the electrically charged particles in the ionosphere would lead to anomalies in radio signals between the ground receivers and the GPS satellites, data that scientists can measure.

Scientists detected a disc-shaped rise in electron density in the ionosphere about seven minutes after the earthquake. Concentric waves of fluctuating electron density then flowed out in the ionosphere from this disk at speeds of about 450 to 500 mph (720 to 800 kph). All in all, this disruption was about three times greater than the next largest one ever seen, which came after the 2004 magnitude 9.3 Sumatra earthquake.

The ripples that flowed from the initial disc-shaped disturbance in the ionosphere appear to be linked to the tsunami, a connection that has the potential to save lives. "This signature in space that we can see with GPS could provide early warning that a tsunami is coming," researcher Jann-Yenq "Tiger" Liu, an atmospheric scientist at Taiwan's National Central University, told OurAmazingPlanet.

One important question in determining how much of a warning his phenomenon might provide is: "Is there any detectable precursor in the status of the ionosphere before this disturbance is actually observed?" said atmospheric physicist Gaopeng Lu at Duke University, who did not take part in this study. "In that way, we might be able to predict the occurrence of earthquakes."

Liu and his colleagues detailed their findings online June 28 in the Journal of Geophysical Research-Space Physics.

This story was provided by OurAmazingPlanet, sister site to LiveScience.

The massive March 11 Japan earthquake and its ensuing tsunami were so powerful that they broke off huge icebergs thousands of miles away in Antarctica, according to a new study.

The calving of icebergs (where a huge chunk of ice breaks off from a glacier or ice shelf) from the Sulzberger Ice Shelf in Antarctica was linked to the tsunami, which originated with the magnitude 9.0 earthquake off the coast of the Japanese island of Honshu, by satellite observations of the Antarctic coast immediately after the earthquake.

Icebergs have been reported to calve following earthquakes before, including after the magnitude 6.3 earthquake that struck Christchurch, New Zealand, on Feb 22. But the new finding marks the first direct observation of such a connection between tsunamis and iceberg calving.

After the Japan tsunami was triggered in the Pacific Ocean, Kelly Brunt, a cryosphere specialist at Goddard Space Flight Center in Greenbelt, Md., and colleagues immediately looked south — really far south. Using multiple satellite images, Brunt, Emile Okal of Northwestern University and Douglas MacAyeal of the University of Chicago were able to observe new icebergs floating off to sea shortly after the sea swell of the tsunami reached Antarctica.

"In the past, we've had calving events where we've looked for the source. It's a reverse scenario — we see a calving and we go looking for a source," Brunt said. "We knew right away this was one of the biggest events in recent history — we knew there would be enough swell. And this time we had a source."

To sum up the dynamics of the event: An earthquake off the coast of Japan caused massive waves to explode out from its epicenter. Swells of water swarmed toward an ice shelf in Antarctica, 8,000 miles (13,600 kilometers) away, and about 18 hours after the earthquake occurred, those waves broke off several chunks of ice that together equaled about two times the surface area of Manhattan. According to historical records, this particular piece of ice hadn't budged in at least 46 years before the tsunami came along.

In what could be one of the more lasting observations from this whole event, the bay in front of the Sulzberger shelf was largely lacking sea ice at the time of the tsunami. Sea ice is thought to help dampen swells that might cause this kind of calving. At the time of the Sumatra tsunami in 2004, the potentially vulnerable Antarctic fronts were buffered by a lot of sea ice, Brunt said, and scientists observed no calving events that they could tie to that tsunami.

"There are theories that sea ice can protect from calving. There was no sea ice in this case," Brunt said. "It's a big chunk of ice that calved because of an earthquake 13,000 kilometers away. I think it's pretty cool."

The study was published today (Aug 8) in the online edition of the Journal of Glaciology.

• Image Gallery: This Millennium's Destructive Earthquakes
• 7 Ways the Earth Changes in the Blink of an Eye
• The 10 Biggest Earthquakes in History

The massive 9.0 magnitude earthquake that devastated Japan in March built up stress on other faults in the country, putting some areas, including Tokyo, at risk of aftershocks and even new main shocks over the next few years, scientists have found.

After studying data from Japan’s extensive seismic network, researchers from the Woods Hole Oceanographic Institution (WHOI), Kyoto University and the U.S. Geological Survey (USGS) have identified several areas at risk from the quake, Japan's largest ever, which already has triggered a large number of aftershocks.

Data from the Tohoku earthquake on March 11 has brought scientists a small  step closer to a better assessment of future seismic risk in specific regions, said Shinji Toda of Kyoto University, a lead author of the study.

"Even though we cannot forecast precisely, we can explain the mechanisms involved in such quakes to the public," he said. Still, he added, the findings do bring scientists "a little bit closer" to being able to forecast aftershocks.

The earthquake relieved stress along the part of the fault where it ruptured, decreasing the likelihood of such a temblor happening in the future, but only in some areas. On neighboring portions of the fault or on nearby, different faults, the possibility of an earthquake may have risen, the scientists found.

The quake, the fourth-largest earthquake ever recorded, was also one of the best-recorded quakes in history because of Japan's extensive seismic monitoring network. [Related: Why the Japan Tsunami Was so Big]

This made the quake a "special" one in terms of scientific investigation, Jian Lin of WHOI said in a statement. "We felt we might be able to find something we didn't see before" in previous quakes, he said.

The magnitude 9 quake appears to have influenced large portions of Honshu Island, Toda said. At particular risk, he said, are the Tokyo area, Mount Fuji and central Honshu, including Nagano.

The Kantu fragment, which is close to Tokyo, also experienced an increase in stress. Previous government estimates have put Tokyo at a 70 percent risk for a magnitude 7 earthquake over the next 30 years. The new data from the Tohoku quake increased those odds to "more than 70 percent," Toda said. "That is really high."

Using a model known as Coulomb stress triggering, Lin and his colleagues found measureable increases in stress along faults to the north at Sanriku-Hokobu, south at Off Boso and at the Outer Trench Slope faults east of the quake’s epicenter off the Japan coast near the city of Sendai. "Based on our other studies, these stress increases are large enough to increase the likelihood of triggering significant aftershocks or subsequent main shocks," the researchers wrote in their study.

"There remains a lot of real estate in Japan — on shore and off — that could host large, late aftershocks of the Tohoku quake," said Ross S. Stein of USGS.

This story was provided by OurAmazingPlanet, sister site to LiveScience.

Extraordinarily high-resolution new GPS data from the giant earthquake that struck Chile in 2010 are uncovering new clues about the largest quakes in the world, including the megaquake that devastated Japan last month.

These new readings have revealed, for instance, the actual epicenter and extent of the rupture of the magnitude 8.8 Chile quake, which is the sixth-largest ever recorded.

The world's largest temblors are called megathrust earthquakes. These quakes burst where one tectonic plate gets forced, or subducted, under another. All recorded quakes of magnitude 9 or higher, including the one that recently hit Japan, have been megathrust earthquakes.

Very little is known about the physics of giant earthquakes -- those of 8.5 or greater -- simply because there have been very few of them in recorded history. Now, however, global positioning system, or GPS, receiver stations can measure precisely what happens to the Earth's surface during quakes, allowing researchers to model them in unprecedented detail.

"We were very lucky in that we had installed several instruments right over where the rupture happened," said researcher Christophe Vigny, a geophysicist at the French National Center for Scientific Research in Paris. "We had the capacity to measure changes with an accuracy of a couple of millimeters."

Epicenter re-evaluated

An international team of scientists analyzing the data found that the actual epicenter of the Chile megathrust quake -- the point on the Earth's surface directly above the rupture of a fault -- was apparently about 25 miles (40 kilometers) southwest of initial estimates.

The team was also able to see that the rupture spread across about 310 miles (500 km) of the approximately 2,500-mile-long (4,000 km) zone where the oceanic Nazca Plate is subducting beneath the continental South American Plate.

"Having the exact length of the rupture allows you to assess what stress might remain on the segments that didn't rupture," Vigny told OurAmazingPlanet. "So, about 3,500 kilometers did not break."

The GPS data contain apparent kinks in motion the researchers attribute to variations in rupture direction and speed along the fault. They think this is related to the unusual size of the quake, which ruptured two regions that had been under stress since earlier quakes in the region in 1835 and 1928.

'Locked' faults

As to why this event became a megathrust quake, "we think we know how -- the rupture found the conditions to keep going, and there was a critical moment around 60 seconds when it could have stopped but 'decided' otherwise," Vigny said. "Now, 'why?' is another question. We don't know if this was bound to happen -- that we could have predicted it if we had known all the stress conditions prior to the earthquake -- or if there really is something unpredictable in it."

The scientists note that Japan has a network of hundreds of GPS stations that captured details of the devastating earthquake that hit the country in March. Those details, along with the Chile data, are giving them more insight into these enormous quakes.

"What we are learning from the GPS data from Chile and seem to be learning from the preliminary data from the 2011 Japanese quake is that megathrust quakes seem to occur in faults highly 'locked' beforehand -- that is, where the interface between two tectonic plates are completely locked in place and not moving because of friction," Vigny said. "A lot of energy is building up in these areas, and maybe if we see other systems that aren't completely locked, maybe that's a good sign that megathrust earthquakes might not happen there. But we don't really know for sure -- we have so few quakes that we have this kind of data from to judge."

Other locked faults that may cause megathrust earthquakes include the Nankai Trough south of Japan. "That should break any day soon," Vigny said. There may also be another such system in northern Chile, he added.

The scientists detailed their findings online April 28 in the journal Science.

This story was provided by OurAmazingPlanet, a sister site to LiveScience.

The first two hours of Japan's massive magnitude 9.0 earthquake has revealed surprising information about how such huge earthquakes rupture.

The earthquake ruptured several areas of a fault that in the past have ruptured alone, contrary to what many scientists would have predicted. If the earthquake had recruited still more nearby segments where massive aftershocks struck, the quake could have been even bigger, said Eric Kiser, a graduate student at Harvard University in Cambridge, Mass., who presented data on the first few hours of the rupture at the Seismological Society of America meeting held last week in Memphis, Tenn.

The March 11 earthquake is now the fourth largest ever recorded in the world. The quake struck off the coast of the Tohoku region of Japan, triggering a deadly tsunami that may have killed nearly 30,000 people. The rumbling didn't end with this massive rupture, and it hasn't stopped today. More than 60 aftershocks of magnitude 6.0 or greater have struck the region. [Related: Listen to Japan's Huge Earthquake]

The main rupture lasted more than 3.5 minutes, although most of the energy was released in the first 2 minutes, Kiser told OurAmazingPlanet. The rupture associated with the main shock was about 155 miles (250 kilometers) long and 109 miles (175 km) wide, Kiser said.

Then came the aftershocks.

Over the first few hours after the initial temblor, several aftershocks hit, many with a magnitude of 6.4 or greater. The largest aftershock to date was a magnitude 7.9 that struck less than an hour after the main shock.

All told, the quake ruptured five areas within the region that have previously ruptured as separate earthquakes, according to preliminary data. The fact that these areas linked together during the March 11 quake is probably why it was unexpectedly large, Kiser said.

The way the quake ruptured is contrary to the previously held idea of segmentation — that the fault is segmented into areas that are more likely to rupture individually, said Morgan Page, a seismologist with the U.S. Geological Survey who has been studying the Japan quake.

"That's why the Japanese seismic hazard maps did not assume that an earthquake this large could hit this region — because in previous cases that area did not all rupture together in one big quake," Page told OurAmazingPlanet.

• Japan's Tsunami: How It Happened
• Photos: Japan Earthquake and Tsunami in Pictures
• Japan's Biggest Earthquakes

Email OurAmazingPlanet staff writer Brett Israel at bisrael@techmedianetwork.com. Follow him on Twitter @btisrael.

A number of devastating quakes have struck across the globe in recent years — from Japan to Chile to Haiti — sparking fears that our planet is due to experience even more catastrophic temblors in the near future.

Three research teams have now combed through 110 years' worth of global seismic records to see if we might be caught in a global trend of giant earthquakes.

Some say we are; others disagree.

Megaquake clusters

One pair of researchers found clusters of what they called "megaquakes," earthquakes of magnitude 9.0 or greater.

One cluster involved three such quakes between 1952 and 1964, including the magnitude 9.5 Chile quake of 1960, the largest earthquake ever recorded on Earth. Another, larger, cluster of magnitude 8.6 and higher temblors happened between 1950 to 1965, said Charles Bufe and David Perkins, seismologists with the U.S. Geological Survey in Golden, Colo. They speculate that the magnitude 8.4 Peru quake in 2001 could mark the beginning of a new global sequence of major quakes that we are currently experiencing.

"This isn't doomsday — I don't think large earthquakes will occur over a long period of time — but we're saying there seems to be a cluster right now with a higher than normal probability for large quakes," Bufe told OurAmazingPlanet. "I don't know how long this cluster might last — if we don't get another large earthquake in maybe the next 10 or 12 years, I would say we're probably out of the cluster."

Bufe suggested that by sending seismic waves traveling around and around the planet's surface, very large earthquakes might weaken fault zones that are already very close to failure. "I think there's a more than 50 percent chance we'll see another magnitude 9 quake sometime in the next decade or so," he said.

Just chance?

On the other hand, this apparent recent spike in large quakes could just reflect random fluctuations in global patterns of seismic activity. A statistical study from U.S. Geological Survey researcher Andrew Michael at Menlo Park, Calif., suggests this seeming cluster pattern disappeared once local aftershocks of the large earthquakes are taken into account.

"The most important lesson is that random doesn't mean uniformly distributed in time — instead, random processes create apparent clustering and it is important to carefully consider whether apparent clusters, or times of less activity, go beyond what is expected from a simple random process," Michael told OurAmazingPlanet. "So far, my results show that the apparent clustering is consistent with a random process."

If the apparent clustering of these quakes is a matter of chance, then seismologists can't say whether or not another huge temblor is likely to erupt anytime soon.

"The recent spate of great earthquakes can be explained as a random fluctuation without predictive power for the future," Michael said. He added that global predictions of earthquakes and the damage they inflict should use the longest possible historical record for an area "rather than focusing on the recent past."

Long-term record

Seismologist Richard Aster at the New Mexico Institute of Mining and Technology and his colleagues looked at historical catalogs of earthquakes along with more recent findings to create a long-term record of the cumulative size of earthquakes around the world.

They suggest there were relatively low rates of big earthquakes during the periods 1907 to 1950 and 1967 to 2004. However, they found the rate of large earthquakes increased substantially during the period 1950 to 1967 and appears to be on the rise again since 2004, since the devastating magnitude 9.1 to 9.3 earthquake that struck Indonesia and generated a massive tsunami late that year.

Still, this finding "is not statistically differentiable from randomness," Aster told OurAmazingPlanet.

Progress into understanding whether there are ages of major quakes or not may be slow "because we just don't get that many great earthquakes to produce a better sampling of this natural process," Aster said.

"We only get a few magnitude 9-plus earthquakes per century, for example — fortunately for earthquake risks around the world, these events are rare," Aster said. "There are only 14 earthquakes in the past 111 years greater than magnitude 8.5."

Michael agreed. "The main limitation is that we don't have enough data," he said. "We can't say that clustering doesn't exist. We can only say that the data doesn't let us reject the hypothesis that the data is random. If there was more data, then the results could change — but that will take decades to occur."

The scientists detailed their findings on April 14 at the Seismological Society of America meeting in Memphis, Tenn.

This story was provided by OurAmazingPlanet, a sister site to LiveScience.