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1968 Borrego Mountain Earthquake
The 1968 Borrego Mountain earthquake occurred on April 8, at 18:28 PST, near the unincorporated community of Ocotillo Wells in San Diego County. The moment magnitude () 6.6 strike-slip earthquake struck with a focal depth of . Damage was relatively moderate, and the mainshock was assigned a maximum Modified Mercalli intensity (MMI) of VII (''Very strong''). Shaking was felt in Nevada, and Arizona. It was the largest earthquake to strike California since 1952, and its display of afterslip became the subject of scientific interest. Tectonic setting A simplified tectonic bounday map of the Salton Trough area. Red lines show major faults and arrows indicate fault motion. The San Andreas Fault (SAF) is the main plate boundary that defines the margin between the Pacific and North American Plates in California. It is believed to have formed during the Oligocene. The fault has a length of , of which, it is visible for from the Salton Sea to Point Arena. Divided into four distinc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pacific Standard Time
The Pacific Time Zone (PT) is a time zone encompassing parts of western Canada, the western United States, and western Mexico. Places in this zone observe standard time by subtracting eight hours from Coordinated Universal Time (UTC−08:00). During Daylight saving time in the Americas#Canada, Mexico and the United States, daylight saving time, a time offset of UTC−07:00 is used. In the United States and Canada, this time zone is generically called the Pacific Time Zone. Specifically, time in this zone is referred to as Pacific Standard Time (PST) when standard time is being observed (early November to mid-March), and Pacific Daylight Time (PDT) when daylight saving time (mid-March to early November) is being observed. In Mexico, the corresponding time zone is known as the ''Zona Noroeste'' (Northwest Zone) and observes the same daylight saving schedule as the U.S. and Canada. The largest city in the Pacific Time Zone is Los Angeles, Greater Los Angeles, whose metropolitan ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oligocene
The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the exact dates of the start and end of the epoch are slightly uncertain. The name Oligocene was coined in 1854 by the German paleontologist Heinrich Ernst Beyrich from his studies of marine beds in Belgium and Germany. The name comes from the Ancient Greek (''olígos'', "few") and (''kainós'', "new"), and refers to the sparsity of extant forms of molluscs. The Oligocene is preceded by the Eocene Epoch and is followed by the Miocene Epoch. The Oligocene is the third and final epoch of the Paleogene Period. The Oligocene is often considered an important time of transition, a link between the archaic world of the tropical Eocene and the more modern ecosystems of the Miocene. Major changes during the Oligocene included a global expansion o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Colton, California
Colton is a city in San Bernardino County, California, United States. Nicknamed "Hub City", Colton is located in the Inland Empire region of the state and is a suburb of San Bernardino, California, San Bernardino, approximately south of the city's Downtown San Bernardino, downtown. The population of Colton is 52,154 according to the 2010 census, up from 47,662 at the 2000 census. Colton is the site of Colton Crossing, which was one of the busiest at-grade rail transport, railroad crossings in the United States. The crossing was installed in 1882 by the California Southern Railroad to cross the Southern Pacific Railroad tracks while building northward from San Diego. As a result of railroad acquisitions and mergers, this became the point at which the Burlington Northern Santa Fe's "Southern Transcontinental Route" crossed the Union Pacific's "Sunset Route". As traffic on each line began to soar in the mid-1990s, fueled largely by the vast increase in imports passing through the p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
San Bernardino, California
San Bernardino (; Spanish for "Saint Bernardino") is a city and county seat of San Bernardino County, California, United States. Located in the Inland Empire region of Southern California, the city had a population of 222,101 in the 2020 census, making it the 18th-largest city in California. San Bernardino is the economic, cultural, and political hub of the San Bernardino Valley and the Inland Empire. The governments of El Salvador, Guatemala, and Mexico have established the metropolitan area’s only consulates in the downtown area of the city. Additionally, San Bernardino serves as an anchor city to the 3rd largest metropolitan area in California (after Los Angeles and San Francisco) and the 13th largest metropolitan area in the United States; the San Bernardino-Riverside MSA. Furthermore, the city’s University District serves as a college town, as home to California State University, San Bernardino. San Bernardino was named in 1810, when Spanish priest Francisco Du ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
San Jacinto Mountains
The San Jacinto Mountains (''Avii Hanupach''Munro, P., et al. ''A Mojave Dictionary''. Los Angeles: UCLA. 1992. in Mojave) are a mountain range in Riverside County, located east of Los Angeles in southern California in the United States. The mountains are named for one of the first Black Friars, Saint Hyacinth (San Jacinto in Spanish), who is a popular patron in Latin America. Geography The range extends for approximately from the San Bernardino Mountains southeast to the Santa Rosa Mountains. The San Jacinto Mountains are the northernmost of the Peninsular Ranges, which run from Southern California to the southern tip of the Baja California Peninsula. The highest peak in the range is San Jacinto Peak (3,302 m; 10,834 ft), and the range is also a Great Basin Divide landform for the Salton Watershed to the east. The Coachella Valley stretches along the eastern side of the range, including the cities of Palm Springs and Rancho Mirage. San Gorgonio Pass separates th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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. Fault characteristics The Elsinore fault zone, not including Whittier, Chino, and Laguna Salada faults, is long with a slip-rate of 4.0 millimeters/year (0.15 in/yr). It is estimated that this zone is capable of producing a quake of 6.5–7.5 MW. The projected interval between major rupture events is 250 years. The last major rupture event on the main Elsinore fault was in 1910 with a 6 MW earthquake centered just northwest of the city of Lake Elsinore. Fault segments and geography The fault runs from the mountainous Peninsular Ranges region between El Centro and San Diego, northwest to the Chino Hills range and Chino Hills. On the southern end of the fault zone is the southeastern extension of the Elsi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
San Jacinto Fault Zone
The San Jacinto Fault Zone (SJFZ) is a major strike-slip fault zone that runs through San Bernardino, Riverside, San Diego, and Imperial Counties in Southern California. The SJFZ is a component of the larger San Andreas transform system and is considered to be the most seismically active fault zone in the area. Together they relieve the majority of the stress between the Pacific and North American tectonic plates. The SJFZ itself consists of many individual fault segments, some of which have only been individualized as recently as the 1980s, but activity along the line of faults has been documented since the 1890s. One segment of the SJFZ, the Anza seismic gap, has not experienced any major activity since instrumental records have been kept. Each segment was evaluated for its seismic risk and was assigned a probability for the occurrence of a large rupture for the thirty-year period starting in 1995. While several of the large earthquakes along the SJFZ have not resulted in sig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rose Canyon Fault
The Rose Canyon Fault is a right-lateral strike-slip fault running in a north-south direction through San Diego County, California.Hart, E.W., Bryant, W.A., Wills, C.J., Treiman, J.A., and Kahle, J.E."Summary Report: Fault Evaluation Program, 1987–1988, Southwestern Basin and Range Region and Supplemental Areas." Department of Conservation, Division of Mines and Geology Open-File Report, 1989. Retrieved March 2, 2010. Extent The Rose Canyon Fault is about in length. It starts in the Mission Valley area and heads past Mt. Soledad and La Jolla into the Pacific Ocean where it joins other faults such as the Oceanside Fault.Monroe, Robert"Finding Faults" 2002. Retrieved March 2, 2010. Current state Not much is known about the Rose Canyon fault, though its slip-rate is thought to be 1.1 mm/year. The Rose Canyon Fault has sustained at least one late Holocene rupture, with the date of the earthquake estimated to be after AD 1450 and most likely prior to construction of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Imperial Fault
The Imperial Fault Zone is a system of geological faults located in Imperial County in the Southern California region, and adjacent Baja California state in Mexico. It cuts across the border between the United States and Mexico. Geology The Imperial Fault Zone is a right lateral-moving strike-slip fault, representing the northernmost transform fault associated with the East Pacific Rise. It is connected to the San Andreas Fault by the Brawley Seismic Zone. It terminates on its southern end at the Cerro Prieto 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/haza ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pull-apart Basin
In geology, a basin is a region where subsidence generates accommodation space for the deposition of sediments. A pull-apart basin is a structural basin where two overlapping (en echelon) strike-slip faults or a fault bend creates an area of crustal extension undergoing tension, which causes the basin to sink down. Frequently, the basins are rhombic or sigmoidal in shape. Dimensionally, basins are limited to the distance between the faults and the length of overlap.Frisch, Wolfgang, Martin Meschede, and Ronald C. Blakey. ''Plate tectonics: Continental drift and mountain building''. Springer, 2010. Pull-apart basins are also referred to as overlapping-tension-zones (OTZ). Mechanics and fault configuration The inhomogeneity and structural complexity of continental crust causes faults to deviate from a straight course and frequently causes bends or step-overs in fault paths. Bends and step-overs of adjacent faults become favorable locations for extensional and compressional str ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transtension
Transtension is the state in which a rock mass or area of the Earth's crust experiences both ''extensive'' and ''transtensive'' shear. As such, transtensional regions are characterised by both extensional structures ( normal faults, grabens) and wrench structures (strike-slip faults). In general, many tectonic regimes that were previously defined as simple strike-slip shear zones are actually transtensional. It is unlikely that a deforming body will experience 'pure' extension or 'pure' strike-slip. Transtensional shear zones are characterized by the co-existence of different structures, related to both strike-slip shear and extension. End member structures include pure strike-slip faults and purely extensional ("normal") dip-slip faults. Faults which have components of both (termed 'oblique' slip faults) are abundant. Releasing bend ''Releasing bends'' are transtensional structures that form where the orientation of a strike-slip fault becomes oblique to the regional slip vector ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
