In addition to the 1906 rupture of the San Andreas fault in northern California, the San Andreas fault in south-central California also experienced a similar size earthquake in 1857, rupturing the San Andreas fault from Parkfield to just northwest of San Bernardino. Plate Boundary Ruptures Along Western North America Earthquakes in the Bay Area reflect the relative motion of the Pacific and North America plates. Notice how the location of earthquakes are concentrated along the plate boundaries of the Earth. The following file records earthquake activity around the world for the past week. Of those, nearly 100,000 can be felt, and 100 cause damage. You may be surprised to learn that 500,000 detectable earthquakes occur globally each year. California is also one of the few places in the world where faults “creep”, that is, the fault slip is slow and continuous and occurs aseismically, which is to say that this slip does not occur as the result of an earthquake. Earthquakes are also associated with active volcanism and the flow of magma at depth. The word “earthquake” is used to describe both sudden slip on a fault and the resulting ground shaking. Most earthquakes occur in the upper 10-12 miles (15-20 km) of the Earth’s crust as the result of failure on faults caused by the strains induced by plate motions.
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