See aftershock in Webster's New World College Dictionary
noun
a minor earthquake, usually one of a series, that follows a larger earthquake and originates at or near the same place
See aftershock in American Heritage Dictionary 4
(ăfˈtər-shŏkˌ)
noun
A quake of lesser magnitude, usually one of a series, following a large earthquake in the same area.
A further reaction following the shock of a deeply disturbing occurrence or revelation: “The industry continued to reel from aftershocks of a disastrous [year]”(David Lake).