Imperial Fault
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The Imperial Fault Zone is a system of
geological Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Eart ...
faults located in
Imperial County Imperial Count (german: Reichsgraf) was a title in the Holy Roman Empire. In the medieval era, it was used exclusively to designate the holder of an imperial county, that is, a fief held directly ( immediately) from the emperor, rather than from ...
in the
Southern California Southern California (commonly shortened to SoCal) is a geographic and Cultural area, cultural region that generally comprises the southern portion of the U.S. state of California. It includes the Los Angeles metropolitan area, the second most po ...
region, and adjacent
Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
state in Mexico. It cuts across the border between the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
and
Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
.


Geology

The Imperial Fault Zone is a right lateral-moving strike-slip fault, representing the northernmost transform fault associated with the
East Pacific Rise The East Pacific Rise is a mid-ocean rise (termed an oceanic rise and not a mid-ocean ridge due to its higher rate of spreading that results in less elevation increase and more regular terrain), a divergent tectonic plate boundary located along ...
. It is connected to the
San Andreas Fault The San Andreas Fault is a continental transform fault that extends roughly through California. It forms the tectonics, tectonic boundary between the Pacific Plate and the North American Plate, and its motion is Fault (geology)#Strike-slip fau ...
by the
Brawley Seismic Zone The Brawley Seismic Zone (BSZ), also known as the Brawley fault zone, is a predominantly extensional tectonic zone that connects the southern terminus of the San Andreas Fault with the Imperial Fault in Southern California. The BSZ is named for ...
. It terminates on its southern end at the
Cerro Prieto Cerro Prieto ( coc, Wee Ñaay, eng, "Black Hill") is a volcano located approximately 29 km (18 mi) SSE of Mexicali in the Mexican state of Baja California. The volcano lies astride a spreading center associated with the East Pacific R ...
spreading center. The Imperial Fault Zone is thought to accommodate slip from both the San Andreas and the San Jacinto fault zones. However, studies covering the last few hundred years show that the slip rate is insufficient to account for the total slip from the San Andreas system.Treiman, J.Jerome, compiler, 1999, Fault number 132, Imperial fault, in Quaternary fault and fold database of the United States: U.S. Geological Survey website, http://earthquakes.usgs.gov/hazards/qfaults The surface trace is well-located based on mapped surface offsets from historic events.


Earthquake history

The Imperial Fault Zone has a history of earthquakes of moderate magnitude, including several
doublet earthquake __NOTOC__ In seismology, doublet earthquakes – and more generally, multiplet earthquakes – were originally identified as multiple earthquakes with nearly identical waveforms originating from the same location. They are now characterized as sin ...
s. *
1915 Imperial Valley earthquakes The 1915 Imperial Valley earthquakes were two destructive shocks centered near El Centro, California on June 22. The earthquakes measured 6.25 and occurred nearly one hour apart at 19:59 and 20:57 PST. Both shocks were assigned VIII (''Severe'') ...
: Two
magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...
6.25 shocks occurred ~1 hour apart. Six people died and several were injured in the second quake at
Mexicali Mexicali (; ) is the capital city of the Mexican state of Baja California. The city, seat of the Mexicali Municipality, has a population of 689,775, according to the 2010 census, while the Calexico–Mexicali metropolitan area is home to 1,000, ...
, located just inside the Mexican border. Unstable banks of the New and Alamo Rivers caved in many places. *
1940 El Centro earthquake The 1940 El Centro earthquake (or 1940 Imperial Valley earthquake) occurred at 21:35 Pacific Standard Time on May 18 (05:35 UTC on May 19) in the Imperial Valley in southeastern Southern California near the international border of the United St ...
*
1979 Imperial Valley earthquake The 1979 Imperial Valley earthquake occurred at 16:16 Pacific Daylight Time (23:16 UTC) on 15 October just south of the Mexico–United States border. It affected Imperial Valley in Southern California and Mexicali Valley in northern Baja Calif ...
*
2010 Baja California earthquake The 2010 Baja California earthquake (also known as 2010 Easter earthquake, 2010 Sierra El Mayor earthquake, or 2010 El Mayor – Cucapah earthquake) occurred on April 4 (Easter Sunday) with a moment magnitude of 7.2 and a maximum Mercalli intens ...


See also

*
Cerro Prieto Fault The Cerro Prieto Fault is a transform fault located in far northern Baja California. It runs between the Cerro Prieto spreading center located southwest of Mexicali, and the Wagner Basin, another spreading center which lies under the Gulf of Cal ...
*
Gulf of California Rift Zone The Gulf of California Rift Zone (GCRZ) is the northernmost extension of the East Pacific Rise which extends some from the mouth of the Gulf of California to the southern terminus of the San Andreas Fault at the Salton Sink. The GCRZ is an incipi ...
*
Salton Trough The Salton Trough is an active tectonic pull-apart basin, or graben. It lies within the Imperial, Riverside, and San Diego counties of southeastern California, United States and extends south of the Mexico–United States border into the state of ...


References


Further reading

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External links


Southern California Earthquake Data Center website: Imperial Fault Zone
{{- Seismic faults of California Seismic faults of Mexico Strike-slip faults Geology of Imperial County, California Natural history of Baja California Natural history of the Colorado Desert El Centro metropolitan area Imperial Valley Salton Trough