Mainshock

In seismology, the mainshock is the biggest earthquake in a group of shaking events. Sometimes, smaller quakes called foreshocks happen before it. After the mainshock, many smaller quakes called aftershocks usually follow.

Mainshocks matter because they can damage buildings, roads, and other structures. By studying these events, scientists learn more about how the Earth's crust moves. This helps communities build safer places and get ready for future earthquakes.

Foreshock

Main article: Foreshock

A foreshock is a smaller earthquake that happens before a bigger earthquake, called the mainshock. It happens in the same place and time as the mainshock. We can only know it was a foreshock after all the earthquakes in the group have happened.

Aftershock

Main article: Aftershock

In seismology, an aftershock is a smaller earthquake that happens after a larger one. It occurs in the same area because the Earth's crust is still adjusting. Big earthquakes often have many aftershocks. These aftershocks usually get smaller and happen less often over time. Sometimes, a big earthquake can break in steps, causing more than one large shake. These are called doublet earthquakes.