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Epicenter
From Wikipedia, the free encyclopedia
The epicenter or epicentre (ancient Greek: επίκεντρον) is the point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or other underground explosion originates.
Seismic waves propagate spherically out from the hypocenter. After an earthquake has occurred, geologists can find out where the epicenter was located by triangulation of seismographic data from three or more different locations. Seismic shadowing occurs on the opposite side of the Earth from the earthquake epicenter because the liquid outer core absorbs the transverse or shear waves (S-waves), and refracts the longitudinal or compressional (P-waves).
The epicenter is usually the location of greatest damage. However, in some cases the epicenter is above the start of a much larger event. In these cases, damage may be spread across a larger area with the greatest damage possibly occurring some distance from the epicenter. For example, in the magnitude 7.9 2002 Denali Fault Earthquake in Alaska, the epicenter was at the western end of the rupture, but the greatest damage occurred about 330 km away at the eastern end of the rupture zone.