Aftershocks

earthquakes · geology · Earth

Ground settling down. After a big earthquake, the rock underground is cracked and shifted. An aftershock happens when that broken rock adjusts and moves slightly to find a new resting place, causing another quake.

Hundreds or thousands. A single large earthquake can trigger hundreds or even thousands of smaller aftershocks. Scientists can measure and count all of them with special instruments.

Getting smaller over time. Aftershocks follow a pattern where they start strong but get weaker and happen less often as days and weeks pass. Eventually, they stop completely.

Two main quakes. Sometimes an earthquake doesn't happen all at once. Instead, the ground ruptures in two steps, creating two powerful earthquakes called a doublet earthquake, which scientists tell apart from regular aftershocks.