San Andreas Fault

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San Andreas Fault
Location	California, United States
Country	United States
Region	California
Cities	San Francisco, Los Angeles, San Diego
Characteristics
Length	1,200 km (750 mi)
Displacement	20–35 mm/yr (0.79–1.38 in/yr)
Tectonics
Plate	Pacific Plate, North American Plate
Status	Active
Type	Transform fault
Age	30 million years

The San Andreas Fault is a major geological fault in California, United States. It forms the boundary between the Pacific Plate and the North American Plate. The fault extends roughly 1,200 kilometers (750 miles) through California. It is known for producing significant earthquakes and is a key feature in the study of plate tectonics.

Geological Characteristics

The San Andreas Fault is a transform fault, which means it is a type of fault where two tectonic plates slide past one another. The fault is divided into three main segments: the Northern, Central, and Southern segments. Each segment has different characteristics and earthquake potential.

Northern Segment

The Northern segment runs from the town of Hollister to the San Francisco Peninsula. This segment was responsible for the 1906 San Francisco earthquake, one of the most devastating earthquakes in U.S. history.

Central Segment

The Central segment extends from Hollister to Parkfield. This segment is known for its "creeping" behavior, where the plates move slowly and steadily, reducing the likelihood of large earthquakes.

Southern Segment

The Southern segment runs from Parkfield to the Salton Sea. This segment is considered the most likely to produce a major earthquake in the near future.

Historical Earthquakes

The San Andreas Fault has been the source of several significant earthquakes:

• 1857 Fort Tejon earthquake
• 1906 San Francisco earthquake
• 1989 Loma Prieta earthquake

Seismic Activity

The fault is monitored by various organizations, including the United States Geological Survey (USGS). The fault's movement is measured using GPS and other geophysical instruments. Scientists study the fault to better understand earthquake risks and to develop early warning systems.

Impact on California

The San Andreas Fault has a significant impact on the geography and infrastructure of California. It influences the state's landscape, water resources, and urban planning. The fault is a major consideration in the construction of buildings, bridges, and other structures to ensure they can withstand potential earthquakes.

See Also

• Earthquake
• Plate tectonics
• Pacific Plate
• North American Plate
• 1906 San Francisco earthquake
• 1989 Loma Prieta earthquake
• United States Geological Survey