An earthquake is the result of a sudden release of stored energy in the Earth's crust that creates seismic waves.
Earthquakes are accordingly measured with a seismometer, commonly known as a seismograph.
The magnitude of an earthquake is conventionally reported using the Richter scale or a related Moment scale (with magnitude 3 or lower earthquakes being hard to notice and magnitude 7 causing serious damage over large areas).
At the Earth's surface, earthquakes may manifest themselves by a shaking or displacement of the ground.
