The epicenter is the location on the Earth's surface that is directly above the hypocenter (or focus) of an earthquake. The epicenter normally represents the first place where the seismic waves released from the underground earthquake rupture encounter the ground surface.
U.S. Geological Survey (Lead Author);Michael Pidwirny (Contributing Author);Peter Saundry (Topic Editor) "Epicenter". 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 18, 2013 <http://www.eoearth.org/article/Epicenter>