1. Fault activity: Faults in the earth's crust are the main places where earthquakes occur. When the accumulated stress of rocks on both sides of the fault exceeds the strength, sudden dislocation will occur, releasing huge energy and triggering earthquakes.

2. Crustal movement: According to the theory of plate tectonics, the crust is divided into several large and many small plates, which move with each other, collide with each other, squeeze or pull, resulting in crustal deformation and stress accumulation.