What is an aftershock?

After a major earthquake, the crust around the ruptured fault adjusts to a new stress balance, producing a sequence of smaller tremors called aftershocks. They are most common near the original rupture zone and gradually become less frequent and less powerful over time. Aftershocks can still cause serious damage to weakened buildings, slopes, and roads. Large earthquakes often produce many aftershocks, sometimes including a few that are strong enough to be damaging on their own.