San Jacinto Fault Zone

The San Jacinto Fault Zone is a major fault zone in Southern California. It runs for 130 miles (210 km) [ [http://www.data.scec.org/fault_index/sanjacin.html San Jacinto Fault Zone ] ] through San Bernardino, Riverside, San Diego and Imperial Counties. It is considered to be the most seismically active fault zone in Southern California. [ [http://pubs.usgs.gov/of/2004/1455/ Preliminary Geologic Map of the Hemet 7.5' Quadrangle, Riverside County, California ] ]

Fault Characteristics

The San Jacinto Fault Zone is not a continuous fault, as many would expect. It is actually a series dextral strike-slip faults. The San Jacinto Fault Zone accommodates a portion of the deformation caused by the opposing movements between the North American Plate and Pacific Plate. The San Jacinto Fault Zone branches westward from the San Andreas Fault in the Transverse Ranges. The fault zone is characterized by a series of strike-slip faults that cross through the pre-Cretaceous metasedimentary and Cretaceous plutonic rocks of the Peninsular Ranges as well as late Cenozoic sedimentary rocks of the Salton Trough. Throughout the fault zone there are minor compressional, tensional, and oblique zones, but most of the plate motion is taken up by a series of dextral strike-slip faults. [Dibblee, 1954] [Sharp, 1967] [Sanders, 1989]

Nearby Communities

* Lytle Creek
* San Bernardino [ [http://www.pe.com/localnews/sanbernardino/stories/PE_News_Local_B_bseismic05.2b333fc.html Seismic retrofit, new building are ideas for San Bernardino's City Hall | San Bernardino | PE.com | Southern California News | News for Inland Southern California ] ]
* Colton [ [http://www.sci.sdsu.edu/salton/San%20AndreasFaultSyst.html The San Andreas Fault System ] ]
* Loma Linda
* Moreno Valley [http://www.ci.moreno-valley.ca.us/city_hall/general-plan/06gpfinal/ieir/5_6-geo-soils.pdf]
* San Jacinto
* Hemet
* East Hemet
* Valle Vista
* Idyllwild-Pine Cove
* Anza
* Borrego Springs
* Ocotillo Wells

Notable earthquakes

The San Jacinto Fault Zone has had some notable earthquakes in historic times: [ [http://pasadena.wr.usgs.gov/info/cahist_eqs.html California Earthquake History, 1769-Present ] ] [ [http://www.cisn.org/special/evt.05.06.12/ CISN: 6/12/2005 Anza Earthquake ] ]

Note: The GPS coordinates listed are approximate in many instances.
* 1890 - Magnitude 6.5 that occurred in the "San Jacinto or Elsinore Fault region". Typing in the GPS coordinates on a map clearly shows that the earthquake occurred on the former fault. [http://maps.google.com/maps?ll=33.400000,%20-116.3000000?&spn=0.3,0.3&t=h&q=33.400000,%20-116.3000000 GPS Coordinates]
* 1892 - Another magnitude 6.5 occurred in the same region as the 1890 earthquake. Like the 1890 earthquake, GPS coordinates show that the San Jacinto Fault was the catalyst, as well. [http://maps.google.com/maps?ll=33.200000,%20-116.200000?&spn=0.3,0.3&t=h&q=33.200000,%20-116.200000 GPS Coordinates]
* 1899 San Jacinto Earthquake - Magnitude 6.4 earthquake destroys San Jacinto and Hemet. [http://maps.google.com/maps?ll=33.666667,%20-116.833333?&spn=0.3,0.3&t=h&q=33.666667,%20-116.833333 GPS Coordinates]
* 1918 San Jacinto Earthquake - Magnitude 6.9 earthquake strikes the same area that was damaged by an earthquake 19 years earlier, with an epicenter roughly 10 mi NW of the previous earthquake. [http://maps.google.com/maps?ll=33.750000,%20-116.883333‎?&spn=0.3,0.3&t=h&q=33.750000,%20-116.883333 GPS Coordinates]
* 1923 North San Jacinto Fault Earthquake - Magnitude 6.3 earthquake damaged the San Bernardino and Redlands area. Last time the fault, which runs under the I-215/I-10 interchange, ruptured in this area. [http://maps.google.com/maps?ll=34.000000,%20-117.300000?&spn=0.3,0.3&t=h&q=34.000000,%20-117.300000 GPS Coordinates]
* 1937 Terwilliger Valley Earthquake - Magnitude 6.0 [http://maps.google.com/maps?ll=33.400000,%20-116.266667?&spn=0.3,0.3&t=h&q=33.400000,%20-116.266667 GPS Coordinates]
* 1942 Fish Creek Mountains Earthquake - Magnitude 6.3 [http://maps.google.com/maps?ll=33.050000,%20-116.083333?&spn=0.3,0.3&t=h&q=33.050000,%20-116.083333 GPS Coordinates]
* 1954 Arroyo Salada Earthquake - Magnitude 6.2 [http://maps.google.com/maps?ll=33.283333,%20-116.1833333?&spn=0.3,0.3&t=h&q=33.283333,%20-116.1833333 GPS Coordinates]
* 1968 Borrego Mountain Earthquake - Magnitude 6.5 [http://maps.google.com/maps?ll=33.183333,%20-116.133333?&spn=0.3,0.3&t=h&q=33.183333,%20-116.133333 GPS Coordinates]
* 1987 Superstition Hills Earthquake - Magnitude 6.6 (Note: some consider it to have occurred on a fault completely unrelated to the San Jacinto Fault Zone) [http://maps.google.com/maps?ll=33.016667.-115.850000?&spn=0.3,0.3&t=h&q=33.016667,-115.850000 GPS Coordinates]

References