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Seismic deformation
Rupture
The area where rocks move over each other during an earthquake. (See also: Epicenter and Hypocenter.)
S
San Andreas Fault
The name of one of the world’s most famous fault zones. It runs close to the coast in California. The San Andreas Fault system is more that 1,300km long and up to 16km deep.
The average rate of motion across the San Andreas Fault during the past 3 million years
has been 56mm/yr (about the same rate as fingernails grow). This rate means that in 15 million years
Los Angeles will have moved north and will lie in the Pacific Ocean, opposite San Francisco.
Scoria
A general term for all the coarse, rough, often foamlike rock material associated with an eruption. It may be in the form
of bombs thrown out of a volcano or may be carried on the surface of lava during an eruption. (See also: Tephra.)
 Scoria—Fragments of foamy lava.
 Seamount—Seamounts are volcanic islands that rise from the ocean bed. The volcanoes may or may not be active. Many seamounts are ringed by coral reefs. Many do not reach the surface at all.
Seamount
A volcano that rises from the seabed. Many Pacific islands are the tops of seamounts.
Seiche
The to-and-fro movement of an enclosed body of water as a
result of the water being affected by earthquake waves. Lakes and estuaries are all prone to this effect. The swimming pool at the University of Arizona in Tucson lost water from a seiche caused by the 1985 Mexico earthquake— 2,000km away.
Seismic deformation
Earthquake waves cause rocks to change shape, or deform, in two ways: short-term change as the waves pass through an area, and long-term change due to the movement of the fault on which the earthquake took place.
The long-term change can sometimes be spotted as a break in railroad tracks or the shifting of the course of a river.
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