How can one earthquake cause another?

Answer 1

Earthquakes can pressure highly stressed fault lines and trigger subsequent seismic events. If correct, so-called stress triggering theory could help scientists pinpoint areas where earthquakes are imminent.

The earthquakes immediately following one earthquake are called aftershocks. Tectonic plates are moving all the time. The aftershocks can occur because the initial earthquake may have moved things into another position. Then the plates will make additional small adjustments (the aftershocks) to release new pressures that the initial earthquake caused between tectonic plates when they moved.

The fault line between the plates may become less stable and then later an entirely new earthquake may occur at the same or at a close by site. It is the instability of the tectonic plates left after one earthquake that can cause others.

Answer 2

An earthquake cannot directly cause another earthquake. However, the stress changes induced by a large earthquake can trigger smaller earthquakes in adjacent faults by redistributing stress along the Earth's crust. This process is known as "induced seismicity."