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The initial point of rupture is called the hypocenter or focus, while the ground level directly above it is the epicenter. Earthquakes are primarily caused by geological faults, but also by volcanic activity, landslides, and other seismic events. The frequency, type, and size of earthquakes in an area define its seismic activity, reflecting the ...
Millions of minor earthquakes occur every year worldwide, equating to hundreds every hour every day. [15] On the other hand, earthquakes of magnitude ≥8.0 occur about once a year, on average. [15] The largest recorded earthquake was the Great Chilean earthquake of May 22, 1960, which had a magnitude of 9.5 on the moment magnitude scale. [16]
Submarine earthquake, an earthquake that occurs underwater at the bottom of a body of water, especially an ocean. [ 17] Supershear earthquake, an earthquake in which the propagation of the rupture along the fault surface occurs at speeds in excess of the seismic shear wave (S-wave) velocity, causing an effect analogous to a sonic boom. [ 18]
Seismology ( / saɪzˈmɒlədʒi, saɪs -/; from Ancient Greek σεισμός ( seismós) meaning "earthquake" and -λογία ( -logía) meaning "study of") is the scientific study of earthquakes (or generally, quakes) and the generation and propagation of elastic waves through the Earth or other planetary bodies. It also includes studies of ...
Earthquakes trace the path of the downward-moving plate as it descends into asthenosphere, a trench forms, and as the subducted plate is heated it releases volatiles, mostly water from hydrous minerals, into the surrounding mantle. The addition of water lowers the melting point of the mantle material above the subducting slab, causing it to melt.
The primary purpose of a seismometer is to locate the initiating points of earthquake epicenters. The secondary purpose, of determining the 'size' or magnitude must be calculated after the precise location is known. [citation needed] The earliest seismographs were designed to give a sense of the direction of the first motions from an earthquake.
Earthquake environmental effects are the effects caused by an earthquake, including surface faulting, tsunamis, soil liquefactions, ground resonance, landslides and ground failure, either directly linked to the earthquake source or provoked by the ground shaking. [ 1] These are common features produced both in the near and far fields, routinely ...
A simple seismometer, sensitive to up-down motions of the Earth, is like a weight hanging from a spring, both suspended from a frame that moves along with any motion detected. The relative motion between the weight (called the mass) and the frame provides a measurement of the vertical ground motion. A rotating drum is attached to the frame and ...