epicentrum

Epicentrum is the point on the Earth’s surface that lies directly above the hypocenter (or focus) of an earthquake. The hypocenter is the location within the crust where the earthquake originates, while the epicenter is the surface projection of that point. The epicenter is a reference location used in reporting and analyzing seismic events, but it does not by itself indicate the maximum shaking area, which is influenced by depth, rupture extent, geology, and fault orientation.

Etymology and usage: the term comes from Greek roots meaning “upon center.” In English, the standard term is epicenter or epicentre, while epicentrum appears in several other languages as a direct loan or cognate for the same concept.

Determination: scientists locate epicenters by deploying seismic stations that record the arrival times of seismic waves, particularly P-waves and S-waves. The difference in their travel times increases with distance from the source. Using these arrival times at multiple stations, the epicenter is triangulated, and the depth of the hypocenter is estimated to determine the earthquake’s full coordinates.

Relation to impact: shaking intensity at a given location depends on many factors beyond distance to the epicenter, including subsurface geology, depth, rupture direction, and local amplification. As a result, the epicenter can be distant from the area experiencing the strongest ground motion.

In seismology, the epicenter remains a fundamental reference point for locating earthquakes, analyzing rupture processes, and communicating event information to the public and authorities.