An aftershock's an earthquake that occurs after a previous earthquake (the main shock). An aftershock's in the same region of the main shock but's always of smaller magnitude strength. If an aftershock's larger than the main shock, the aftershock's redesignated as the main shock and the original main shock's redesignated as a foreshock. Aftershocks are smaller earthquakes formed as the crust around the displaced fault plane adjusts to the effects of the main shock. Distribution of aftershocks M… (More on Aftershock)