Earthquake terminology and general definition

Summary

An earthquake (also called a quake, tremor, or temblor) is the shaking of Earth’s surface caused by a sudden release of energy in the lithosphere that generates seismic waves. In the most general sense, the term can describe any seismic event that produces seismic waves, whether it occurs naturally or is triggered by human activities such as mining, fracking, or nuclear testing. Earthquakes range from very weak events that may not be felt to severe events that can throw people and objects into the air, damage critical infrastructure, and devastate entire cities. The initial point where rupture begins is called the hypocenter (or focus), while the epicenter is the point on the ground directly above the hypocenter. Earthquakes are primarily caused by rupture and movement along geological faults, but they can also be associated with other processes such as volcanism and landslides. Related concepts include seismic activity (the frequency, type, and size of earthquakes in an area over time) and seismicity (the average rate of seismic energy released per unit volume at a location in Earth.

Key Points

• 1

  An earthquake is surface shaking produced by a sudden energy release that generates seismic waves.

• 2

  The hypocenter (focus) is the rupture start point; the epicenter is directly above it on the surface.

• 3

  Earthquakes are mostly caused by fault rupture, but can also be linked to volcanism, landslides, and human-induced activities.