A rare, powerful 5.8-magnitude earthquake shook the East Coast United States on August 23. Damage was light, but millions of people were surprised and unnerved by the event. The earthquake occurred near Mineral, Virginia, about 100 miles southwest of Washington, DC. It was a shallow earthquake, and shaking was recorded all along the Appalachians, from Georgia to New England. There have been several aftershocks and more are expected.
An earthquake is the result of a sudden release of energy in the Earth'scrustthat creates seismic waves. It is estimated that around 500,000 earthquakes occur each year, detectable with current instrumentation. About 100,000 of these can be felt. Earthquakes are caused mostly by rupture of geological faults, but also by other events such as volcanic activity, landslides, mine blasts, and nuclear tests. Earthquakes may last only a few seconds or may continue for up to several minutes. They can occur at any time of the day or night and at any time of the year.
Scientists have learned a lot about earthquakes, but there is still much that we don't know, like how to accurately forecast them.