San Jacinto Fault Zone
Encyclopedia
The San Jacinto Fault Zone is a major fault zone in Southern California
. It runs for 130 miles (209.2 km) through San Bernardino
, Riverside
, San Diego
and Imperial
Counties. It is considered to be the most seismically active fault zone in Southern California. The San Jacinto Fault Zone generally lies west of the larger, more infamous San Andreas Fault
while running parallel and to the east of the Elsinore Fault Zone
. Both the San Jacinto and Elsinore Fault Zones are classified as part of the San Andreas Fault System, relieving the majority of the stress between the Pacific Plate
and North American Plate
.
. The fault zone is characterized by a series of strike-slip faults that cross through the pre-Cretaceous
metasedimentary and Cretaceous Plutonic rock 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 crustal stress is relieved by horizontal, strike-slip motion.
Note: The GPS coordinates listed are approximate in many instances.
Southern California
Southern California is a megaregion, or megapolitan area, in the southern area of the U.S. state of California. Large urban areas include Greater Los Angeles and Greater San Diego. The urban area stretches along the coast from Ventura through the Southland and Inland Empire to San Diego...
. It runs for 130 miles (209.2 km) through San Bernardino
San Bernardino County, California
San Bernardino County is a county in the U.S. state of California. As of the 2010 census, the population was 2,035,210, up from 1,709,434 as of the 2000 census...
, Riverside
Riverside County, California
Riverside County is a county in the U.S. state of California. One of 58 California counties, it covers in the southern part of the state, and stretches from Orange County to the Colorado River, which forms the state border with Arizona. The county derives its name from the city of Riverside,...
, San Diego
San Diego County, California
San Diego County is a large county located in the southwestern corner of the US state of California. Hence, San Diego County is also located in the southwestern corner of the 48 contiguous United States. Its county seat and largest city is San Diego. Its population was about 2,813,835 in the 2000...
and Imperial
Imperial County, California
Imperial County is a county located in the Imperial Valley, in the far southeast of the U.S. state of California, bordering both Arizona and Mexico. It is part of the El Centro Metropolitan Area, which encompasses all of Imperial County. The population as of 2000 was 142,361. The county seat is the...
Counties. It is considered to be the most seismically active fault zone in Southern California. The San Jacinto Fault Zone generally lies west of the larger, more infamous San Andreas Fault
San Andreas Fault
The San Andreas Fault is a continental strike-slip fault that runs a length of roughly through California in the United States. The fault's motion is right-lateral strike-slip...
while running parallel and to the east of the Elsinore Fault Zone
Elsinore Fault Zone
The Elsinore Fault Zone is a large right-lateral strike-slip geological fault structure in Southern California. The fault is part of the trilateral split of the San Andreas fault system and is one of the largest, though quietest faults in Southern California....
. Both the San Jacinto and Elsinore Fault Zones are classified as part of the San Andreas Fault System, relieving the majority of the stress between the Pacific Plate
Pacific Plate
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres, it is the largest tectonic plate....
and North American Plate
North American Plate
The North American Plate is a tectonic plate covering most of North America, Greenland, Cuba, Bahamas, and parts of Siberia, Japan and Iceland. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia. The plate includes both continental and oceanic crust...
.
Fault Characteristics
The San Jacinto Fault Zone is not a continuous fault, but a series of faults focused along the same general axis. These related faults are dextral, exhibiting right lateral-moving horizontal motion (strike-slip). 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 RangesTransverse Ranges
The Transverse Ranges are a group of mountain ranges of southern California, in the Pacific Coast Ranges physiographic region that runs along the Pacific coast from Alaska to Mexico in North America. The Transverse Ranges begin at the southern end of the California Coast Ranges and lie between...
. The fault zone is characterized by a series of strike-slip faults that cross through the pre-Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
metasedimentary and Cretaceous Plutonic rock of the Peninsular Ranges
Peninsular Ranges
The Peninsular Ranges are a group of mountain ranges, in the Pacific Coast Ranges, which stretch from southern California in the United States to the southern tip of Mexico's Baja California peninsula; they are part of the North American Coast Ranges that run along the Pacific coast from Alaska...
as well as late Cenozoic
Cenozoic
The Cenozoic era is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 mya to the present. The era began in the wake of the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and...
sedimentary rocks of the Salton Trough
Salton Sink
The Salton Sink is a geographic sink in the Coachella and Imperial valleys of southeastern California. It is in the Colorado Desert subregion of the Sonoran Desert ecoregion...
. Throughout the fault zone there are minor compressional, tensional, and oblique zones, but most of the crustal stress is relieved by horizontal, strike-slip motion.
Fault Segments
The San Jacinto Fault consists of at least three major segments- The Claremont Segment begins at the intersection of the San Jacinto and San Andreas Faults and cuts southward through the San BernardinoSan BernardinoSan Bernardino, California is a large city in the Inland Empire Metropolitan Area of Southern California.San Bernardino may also refer to:-Landforms:*San Bernardino , a torrent that flows through the Italian province of Verbano-Cusio-Ossola...
Basin. Between 1.5 and 1.0 Ma this section has experienced ~25 km of slip, implying a long-term slip rate of 16–25 mm/yr . - The Clark Section continues southward from the San Bernardino Basin and travels along the flank of the San Jacinto MountainsSan Jacinto MountainsThe San Jacinto Mountains are a mountain range east of Los Angeles in southern California in the United States. The mountains are named for Saint Hyacinth . The Pacific Crest Trail runs along the spine of the range.The range extends for approximately from the San Bernardino Mountains southeast to...
. 24–25 km of right-lateral slip has been documented , with initiation of slip at 1.5 ± 0.2 Ma, implying 13–18 mm/yr . Rockwell et al. suggest that Late PleistocenePleistoceneThe Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
slip rates have been lower . - The Coyote Creek Section consists of both the Clark and Coyote Creek Faults. The Coyote Creek Fault has an estimated HoloceneHoloceneThe Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
slip rate of 3–5 mm/yr , and a much larger average slip rate of 11 ± 3 mm/yr since 600 ± 100 ka .
Nearby Communities
- Lytle CreekLytle Creek, CaliforniaLytle Creek is a census-designated place in San Bernardino County. It is about northwest of downtown San Bernardino and 10 miles from the cities of Fontana and Rialto. This small remote community is located in a large southeast-trending canyon on the eastern portion of the San GabrielMountains...
- San BernardinoSan Bernardino, CaliforniaSan Bernardino is a city located in the Riverside-San Bernardino metropolitan area , and serves as the county seat of San Bernardino County, California, United States...
- ColtonColton, CaliforniaColton is a city in San Bernardino County, California, United States. The city is located in the Inland Empire region of the state and is approximately 57 miles east of Los Angeles. The population of Colton is 52,154 according to the 2010 census, up from 47,662 at the 2000 census.Colton is the...
- Loma LindaLoma Linda, CaliforniaLoma Linda is a city in San Bernardino County, California, United States, that was incorporated in 1970. The population was 23,261 at the 2010 census, up from 18,681 at the 2000 census...
- Moreno ValleyMoreno Valley, CaliforniaMoreno Valley is a city located in Riverside County, California.A relatively young city, its rapid growth in the 1980s and the first decade of the 21st century made it second-largest city in Riverside County by population, and one of the Inland Empire's population centers. As of the 2010 census,...
- San JacintoSan Jacinto, CaliforniaSan Jacinto is a city in Riverside County, California, U.S.A. It was named after Saint Hyacinth and is located at the north end of the San Jacinto Valley, with Hemet to its south. The mountains associated with the valley are the San Jacinto Mountains. The population was 44,199 at the 2010...
- HemetHemet, CaliforniaHemet is a city in the San Jacinto Valley in Riverside County, California, United States. It covers a total area of , about half of the valley, which it shares with the neighboring city of San Jacinto. The population was 78,657 at the 2010 census....
- East HemetEast Hemet, CaliforniaEast Hemet is a census-designated place in Riverside County, California, United States, located east of Hemet. East Hemet is in an unincorporated area outside the city limits of Hemet...
- Valle VistaValle Vista, CaliforniaValle Vista is a census-designated place in Riverside County, California, United States. The population was 14,578 at the 2010 census, up from 8,356 at the 2000 census.-Geography:Valle Vista is located at ....
- Idyllwild-Pine CoveIdyllwild-Pine Cove, CaliforniaIdyllwild, Pine Cove, and Fern Valley are three adjacent communities, of which Idyllwild is the largest, located in the San Jacinto Mountains in Riverside County, California, United States. "Mile-high Idyllwild" is a popular southern California mountain resort about one mile in altitude...
- AnzaAnza, CaliforniaAnza is a census-designated place located in southern Riverside County, California, in the Anza Valley, a semi-arid region at a mean elevation of above sea level. It is located south of Idyllwild, and approximately southwest of Palm Springs, southeast of Los Angeles, California and...
- Borrego SpringsBorrego Springs, CaliforniaBorrego Springs is a census-designated place in San Diego County, California. The population was 3,429 at the 2010 census, up from 2,535 at the 2000 census. Many residents are seasonal while others remain year round...
- Ocotillo WellsOcotillo Wells, CaliforniaOcotillo Wells is an unincorporated community in San Diego County, California. It is west of the Imperial County line on State Route 78 at an elevation of . The name became official in 1962 when it was adopted for federal use by the Board of Geographic Names. A federally-recognized variant name,...
Notable earthquakes
The San Jacinto Fault Zone has had some notable earthquakes in historic times: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. 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. GPS Coordinates
- 1899 San Jacinto Earthquake - Magnitude 6.4 earthquake destroys San Jacinto and Hemet. 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. 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. GPS Coordinates
- 1937 Terwilliger Valley Earthquake - Magnitude 6.0 GPS Coordinates
- 1942 Fish Creek Mountains Earthquake - Magnitude 6.3 GPS Coordinates
- 1954 Arroyo Salada Earthquake - Magnitude 6.2 GPS Coordinates
- 1968 Borrego Mountain Earthquake - Magnitude 6.5 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) GPS Coordinates
- 2010 Borrego Springs - Magnitude 5.4. This quake was believed by seismologists to have been possibly triggered by the strong earthquake which occurred on Easter of the same year near Calexico2010 Baja California earthquakeThe 2010 Baja California earthquake was an earthquake of 7.2 magnitude on the moment magnitude scale. It started south of Guadalupe Victoria, Baja California, Mexico, at a depth of . It occurred at 3:40:41 p.m...
.