Preferred term

Aftershock

Description

An earthquake occurring as a consequence of a larger earthquake (referred to as the mainshock) at roughly the same location. Aftershocks are smaller than the mainshock and within 1-2 fault lengths distance from the mainshock fault. The sequence of such earthquakes following a larger one generally shows a regular decrease in the rate of occurrence, first discovered by Omori (1894), indicating a stress relaxation and redistribution process as the rocks accommodate to their new post-earthquake state. Aftershocks can continue over a period of weeks, months, or years, decreasing in frequency with time. In general, the larger the mainshock, the larger and more numerous the aftershocks, and the longer they will continue.
Earthquake that follows a largest earthquake (referred to as the mainshock) in a sequence of earthquakes occurring in the same area. Aftershocks are generally smaller than the mainshock, and may be observed over a period of weeks, months, or years depending of the mainshock magnitude.