Earthquakes are the result of plate tectonics, or shifting plates in the crust of Earth, and quakes occur when the frictional stress of gliding plate boundaries builds and causes failure at a fault line. In an earthquake, elastic strain energy is released and waves radiate, shaking the ground. Scientists can predict where major temblors might occur in a general sense, but research does not yet allow forecasts for specific locations or accurate predictions of timing. Major earthquakes, some generating tsunamis, have leveled entire cities and affected whole countries. Relatively minor earthquakes can also be induced, or caused by human activity, including extraction of minerals from Earth and the collapse of large buildings.
Oklahoma is not known for its earthquakes, but in recent years episodes of ground shaking have surged, with the U.S. Geological Survey releasing a rare warning last May saying the risk of a damaging earthquake in Oklahoma had significantly increased.
The planet is crawling with tiny spies: Hidden undersea microphones, instrument-clad satellites and infrared cameras are listening, watching and smelling all the action on planet Earth, from a migrating whale to a meteor crash.