Calming Ragged Nerves from Inside the Tsunami Warning Center

Gerard Fryer got paged about 20 times early Thursday morning Hawaii time, signaling a large earthquake had occurred in Chile and there was a potential for a tsunami.

The 7.2-magnitude aftershock today, linked to the initial 8.8-magnitude quake that struck the area on Feb. 27, did more than shake the ground. It seemed to send some people into a state of panic, according to Fryer, a geophysicist with the Pacific Tsunami Warning Center (PTWC).

"Since then I've pretty much been calming people's ragged nerves," Fryer told LiveScience. "Private citizens in Chile were calling us because they are alarmed. They are really very nervous about the state of earthquakes. This was a very large aftershock."

While the National Emergency Office issued a tsunami alert for areas of Chile, the PTWC said there was "no real tsunami threat," issuing a tsunami information bulletin.

Tell that to the people who felt the aftershock.

"This was a really a big earthquake in anyone's book, and clearly it was felt throughout Chile and Argentina, because we were getting quite a few calls from there," Fryer said. "They ask if there is a tsunami and they actually called while we're still in the middle of working up the event and figuring out what is going on."

They even got calls from Hawaii.

"A lot of people sign up for earthquake pages from the U.S. Geological Survey, and so their cell phone wakes them up in the middle of the night and they check it and the next thing they do is call us. Our job is to tell them what they need to know," Fryer said.

Fryer's pages came from seismographs set up all over the world. A seismograph is a device for measuring the movement of the earth, and consists of a ground-motion detection sensor called a seismometer, coupled with a recording system.

The seismic waves that are recorded get sent to computers, which can look at each signal. "Whenever it sees a big signal it will raise a flag," Fryer said. When there are enough "red flags" in close proximity, that's a sign of a possible tsunami.

The Chilean aftershock was first picked up by a seismometer in South America, then North America and Antarctica, and then out into the wider Pacific Ocean, Fryer said.

"Then we look to see if a tsunami has been generated. We look at tide gauges along the shoreline," he added.

Indeed a tsunami had occurred, albeit a baby one. The gauges showed a 7.9-inch (20 centimeter) increase in tides above average at Valparaiso, Chile.

Though the tsunami threat is over, Fryer said, he feels "sorry for the people."

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