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Tectonic earthquakes occur anywhere on the earth where there is sufficient stored elastic strain energy to drive fracture propagation along a fault plane. The sides of a fault move past each other smoothly and aseismically only if there are no irregularities or asperities along the fault surface that increases the frictional resistance.
Earthquakes are common on the West Coast, with multiple plate boundaries like the San Andreas fault making geologic activity more likely. They are rarer on the East Coast, but they do happen .
Seismic waves produced by sunquakes occur in the photosphere and can travel at velocities of 35,000 kilometres per hour (22,000 mph) for distances up to 400,000 kilometres (250,000 mi) before fading away. [13] On July 9, 1996, a sunquake was produced by an X2.6 class solar flare and its corresponding coronal mass ejection.
Megathrust earthquakes occur at convergent plate boundaries, where one tectonic plate is forced underneath another. The earthquakes are caused by slip along the thrust fault that forms the contact between the two plates. These interplate earthquakes are the planet's most powerful, with moment magnitudes (M w) that can exceed 9.0.
About 55 earthquakes a day – 20,000 a year – are recorded by the National Earthquake Information Center. Most are tiny and barely noticed by people living where they happen. But some are ...
Most earthquakes occur at the boundaries between tectonic plates, such as the 'Ring of Fire' around the Pacific Ocean plate. Earthquakes within a tectonic plate, like those in the eastern U.S., do ...
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. The 2001 Nisqually and 1949 Olympia earthquakes were also intraslab events. [13]
A type of seismic zone is a Wadati–Benioff zone which corresponds with the down-going slab in a subduction zone. [2] The world's greatest seismic belt, known as the Circum-Pacific seismic belt, [3] is where a majority of the Earth's quakes occur.