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In its most general sense, the word earthquake is used to describe any seismic event that generates seismic waves. Earthquakes can occur naturally or be induced by human activities, such as mining, fracking, and nuclear tests. The initial point of rupture is called the hypocenter or focus, while the ground level directly above it is the epicenter.
Plate tectonics (from Latin tectonicus, from Ancient Greek τεκτονικός (tektonikós) 'pertaining to building') [1] is the scientific theory that Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago.
An interplate earthquake occurs at the boundary between two tectonic plates. Earthquakes of this type account for more than 90 percent of the total seismic energy released around the world. [1] If one plate is trying to move past the other, they will be locked until sufficient stress builds up to cause the plates to slip relative to each other.
In the Himalayan region, where the Indian plate subducts under the Eurasian plate, the largest recorded earthquake was the 1950 Assam–Tibet earthquake, at magnitude 8.7. It is estimated that earthquakes with magnitude 9.0 or larger are expected to occur at an interval of every 800 years, with the highest boundary being a magnitude 10, though ...
The boundary between Okhotsk microplate and Pacific plate is a subduction zone, where the Pacific plate subducts beneath the Okhotsk Plate. Many strong megathrust earthquakes occurred here, some of them among the largest on world record, including the Kamchatka earthquakes of 1737 (estimated M9.0~9.3) and 1952 (M9.0).
The relative movement of the plates typically ranges from zero to 10 cm annually. Faults tend to be geologically active, experiencing earthquakes, volcanic activity, mountain-building, and oceanic trench formation. Tectonic plates are composed of the oceanic lithosphere and the thicker continental lithosphere, each topped by its own kind of crust.
These smaller plates are often not shown on major plate maps, as the majority of them do not comprise significant land area. For purposes of this list, a minor plate is any plate with an area less than 20 million km 2 (7.7 million sq mi) but greater than 1 million km 2 (0.39 million sq mi).
Intraslab earthquakes at depths 20–60 km (12–37 mi) are considered shallow earthquakes and can be destructive to cities. One of the deadliest earthquakes of the 20th century was the 1970 Ancash earthquake, measuring M w 7.9 and occurring off the coast of Peru.