What is an earthquake?
An earthquake is the sudden movement of the Earth caused by the abrupt release of accumulated strain along a fault in the interior. The released energy passes through the Earth as seismic waves (low-frequency sound waves), which cause the shaking. Seismic waves continue to travel through the Earth after the fault motion has stopped. Recordings of earthquakes, called seismograms, illustrate that such motion is recorded all over the Earth for hours, and even days, after an earthquake. Earthquakes are one of the most destructive natural phenomena and occur with very little warning.
Scholz, Christopher H. and Shedlock, Kaye M. (2017). Earthquake. In Access Science. McGraw-Hill Education. https://doi.org/10.1036/1097-8542.209800