Which process is responsible for most earthquakes?

Most earthquakes are caused by the sudden release of stress along faults as tectonic plates move. Over time, rocks deform elastically until friction is overcome and the fault slips, sending seismic waves through the ground. This is why earthquakes are common near plate boundaries, especially in subduction zones, transform faults, and rift zones. The 1960 Valdivia earthquake in Chile, the largest instrumentally recorded at magnitude 9.5, was a dramatic example of plate-boundary rupture. Earthquake science relies on seismic networks to locate these events and measure their size.