Earthquakes are caused by the sudden release of energy in the Earth's crust that generates seismic waves, shaking the ground violently. The hypocenter is the location below the surface where the earthquake originates, and the epicenter is the point directly above it on the Earth's surface. An earthquake is defined as any sudden shaking of the ground caused by seismic waves traveling through the planet's rocks.

1. Definition
earthquake, any sudden shaking of the ground
caused by the passage of seismic waves through
Earth's rocks.
An earthquake is a sudden, violent shaking of the
ground caused by the sudden release of energy in
the Earth's lithosphere that creates seismic waves.
The location below the earth’s surface where the
earthquake starts is called the hypocenter, and the
location directly above it on the surface of the earth is
called the epicenter.