Earthquake

            An earthquake (also known as a quake, tremor or temblor) is the result of a sudden release of energy in theEarth crust that creates Seismic Waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time.Earthquakes are measured using observations from seismometers. 

             Tectonic Eartquake. These occur when rocks in the earth's crust break due to geological forces created by movement of Tectonic plates Another type,volcanic earthquakes, occur in conjunction with volcanic activity. Collapse earthquakes are small earthquakes in underground caverns and mines.Landslip a slide of a large mass of dirt and rock down a mountain or cliff landslide.

            Earthquakes are caused by faulting, a sudden lateral or vertical movement of rock along a rupture (break) surface. 

             The epicenter is the point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or underground explosion originates. The word derives from the New Latin noun epicentrum, the latinisation of the ancient Greek adjective ἐπίκεντρος (epikentros), "occupying a cardinal point, situated on a centre", from ἐπί (epi) "on, upon, at" and κέντρον (kentron) "centre".Focus refers to the depth at which an earthquake occurs. Earthquakes occurring at a depth of less than 70 km are classified as 'shallow-focus' earthquakes, while those with a focal-depth between 70 and 300 km are commonly termed 'mid-focus' or 'intermediate-depth' earthquakes.

             Foreshocks are earthquakes which precede larger earthquakes in the same location. Aftershocks are smaller earthquakes which occur in the same general area during the days to years following a larger event or "mainshock", defined as within 1-2 fault lengths away and during the period of time before the background seismicity level has resumed. 

            The Magnitude indicates the amount of energy released at the source (or epicentre) and is measured by the open-ended Richter Scale.The intensity of an earthquake at a particular locality indicates the violence of earth motion produced there by the earthquake.