Friction between tectonic plates, which further lock them, leads to earthquakes.
Step-by-step explanation:
Tectonic plates move slowly, but at times there is friction between them. This friction locks them, and that leads to difficulty in movement. Whereas, other tectonic plates keep on moving, which leads to high pressure at the locked section.
This lock section tries to resist pressure, and the movement of plates is passed to each other. This rapid movement leads to a tectonic earthquake. The energy released during the change of plates causes the Earth's crust to shake, and that's how we feel shaking.