This article is about the natural seismic phenomenon.For other uses,see Earthquake (disambiguation).
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves.Earthquakes are recorded with a seismometer,also known as a seismograph.The moment magnitude of an earthquake is conventionally reported,or the related and mostly obsolete Richter magnitude,with magnitude 3 or lower earthquakes being mostly imperceptible and magnitude 7 causing serious damage over large areas.Intensity of shaking is measured on the modified Mercalli scale.
At the Earth's surface,earthquakes manifest themselves by a shaking and sometimes displacement of the ground.When a large earthquake epicenter is located offshore,the seabed sometimes suffers sufficient displacement to cause a tsunami.The shaking in earthquakes can also trigger landslides and occasionally volcanic activity.
