The hypocenter (or focus) is the point beneath the ground surface where an earthquake rupture occurs. Above the hypocenter on the Earth's surface is the epicenter. (Image Source: Michael Pidwirny).
This article has been reviewed by the following Topic Editor: Peter Saundry
The hypocenter (or focus) of an earthquake is the point within the earth where an earthquake rupture occurs. Energy released by the rupture travels away from the hypocenter in the form of seismic waves that cause the Earth's rock interior, surface sediments, and surface to shake and deform through compression and expansion. The epicenter is the point directly above the hypocenter on the surface of the Earth.
U.S. Geological Survey (Lead Author);Michael Pidwirny (Contributing Author);Peter Saundry (Topic Editor) "Hypocenter". In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth March 12, 2011; Last revised Date December 28, 2011; Retrieved May 19, 2013 <http://www.eoearth.org/article/Hypocenter>