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earthquake facts
Home to about 75% of the world's volcanoes and 90% of its earthquakes, the circum-Pacific Ring of Fire is the most seismically and volcanically active zone in the world. Measuring roughly 25,000-miles, the Ring of Fire is a chain of volcanoes and seismically active sites along the areas where the Pacific Plate meets surrounding tectonic plates.
earthquake faults
A fault is a fracture or zone of fractures between two blocks of
rock. Faults allow the blocks to move relative to each other. This
movement may occur rapidly, in the form of an earthquake - or may
occur slowly, in the form of creep. Faults may range in length
from a few millimeters to thousands of kilometers. Earth
scientists use the angle of the fault with respect to the surface
(known as the dip) and the direction of slip along the fault to
classify faults.
Below documents three main types.
normal fault
A dip-slip fault in which the block above the fault moves downward relative to the block below. This type of faulting occurs in response to extension and are usually found along divergent plate boundaries. It is often observed in the Western United States Basin and Range Province and along oceanic ridge systems.
USGSreverse fault
A dip-slip fault in which the upper block, above the fault plane, moves up and over the lower block. This type of faulting is common in areas of compression, such as regions where one plate is being subducted under another as in Japan. When the dip angle is shallow, a reverse fault is often described as a thrust fault.
USGSstrike-slip fault
Vertical (or nearly vertical) fractures where the blocks have mostly moved horizontally. The fault motion of a strike-slip fault is caused by shearing forces. If the block on the far side of the fault moves to the left, it is a left-lateral fault. If the block on the far side moves to the right, the fault is called right-lateral.
NSF