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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 California. The earthquake had a relatively shallow hypocenter and caused property damage in the United States estimated at US$30 million. The irrigation systems in the Imperial Valley were badly affected, but no deaths occurred. It was the largest earthquake to occur in the contiguous United States since the 1971 San Fernando earthquake eight years earlier. The earthquake was 6.5 on the scale, with a maximum perceived intensity of IX (''Violent'') on the Mercalli intensity scale. However, most of the intensity measurements were consistent with an overall maximum intensity of VII (''Very strong''), and only the damage to a single structure, the Imperial County Services building in El Centro, was judged to be of intensity IX. Several comprehe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fault (geology)
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic forces, with the largest forming the boundaries between the plates, such as the megathrust faults of subduction zones or transform faults. Energy release associated with rapid movement on active faults is the cause of most earthquakes. Faults may also displace slowly, by aseismic creep. A ''fault plane'' is the plane that represents the fracture surface of a fault. A ''fault trace'' or ''fault line'' is a place where the fault can be seen or mapped on the surface. A fault trace is also the line commonly plotted on geologic maps to represent a fault. A ''fault zone'' is a cluster of parallel faults. However, the term is also used for the zone of crushed rock along a single fault. Prolonged motion along closely spaced faults can blur the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pacific Plate
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate. The plate first came into existence 190 million years ago, at the triple junction between the Farallon, Phoenix, and Izanagi Plates. The Pacific Plate subsequently grew to where it underlies most of the Pacific Ocean basin. This reduced the Farallon Plate to a few remnants along the west coast of North America and the Phoenix Plate to a small remnant near the Drake Passage, and destroyed the Izanagi Plate by subduction under Asia. The Pacific Plate contains an interior hot spot forming the Hawaiian Islands. Boundaries The north-eastern side is a divergent boundary with the Explorer Plate, the Juan de Fuca Plate and the Gorda Plate forming respectively the Explorer Ridge, the Juan de Fuca Ridge and the Gorda Ridge. In the middle of the eastern side is a transform boundary with the North American Plate along the San Andreas Fault, and a boundary with the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1892 Laguna Salada Earthquake
The 1892 Laguna Salada earthquake occurred at . It had an estimated moment magnitude scale, moment magnitude of 7.1–7.2 and a maximum perceived intensity of VIII (''Severe''). The shock was centered near the Mexico–United States border and takes its name from a large dry lake bed in Baja California, Mexico. There were no reported casualties, but the event affected the then largely-uninhabited areas of northern Mexico and Southern California. Tectonic setting The Salton Trough is part of the complex plate boundary between the Pacific Plate and the North American Plate where it undergoes a transition from the transform fault, continental transform of the San Andreas Fault system to the series of short Mid-ocean ridge, spreading centers of the East Pacific Rise linked by oceanic transforms in the Gulf of California. The southern part of the trough is divided into two by the Sierra Cucapa and Sierra Mayor ranges forming the Mexicali Municipality, Baja California, Mexicali Valley ... [...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] |
Salton Sea
The Salton Sea is a shallow, landlocked, highly saline body of water in Riverside and Imperial counties at the southern end of the U.S. state of California. It lies on the San Andreas Fault within the Salton Trough that stretches to the Gulf of California in Mexico. Over millions of years, the Colorado River has flowed into the Imperial Valley and deposited alluvium (soil), creating fertile farmland, building up the terrain, and constantly moving its main course and river delta. For thousands of years, the river has alternately flowed into the valley, or diverted around it, creating either a saline lake called Lake Cahuilla, or a dry desert basin, respectively. When the Colorado River flows into the valley, the lake level depends on river flows and the balance between inflow and evaporative loss. When the river diverts around the valley, the lake dries completely, as it did around 1580. Hundreds of archaeological sites have been found in this region, indicating possibly long-ter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 the nearby town of Brawley in Imperial County, California, and the seismicity there is characterized by earthquake swarms. Geology The Brawley Seismic Zone represents the northernmost extension of the spreading center axis associated with the East Pacific Rise which runs up the axis of the Gulf of California and is in the process of rifting the Baja California Peninsula away from the mainland of Mexico, with significant subsidence taking place at southern California's Salton Sea and at Laguna Salada in Baja California. Other major locations along the axis include the Cerro Prieto spreading center located south of Mexicali, and Wagner Basin (a submarine depression in the Gulf of California). The Salton Buttes on the south shore of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Imperial Fault Zone
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/haz ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laguna Salada Fault
The Laguna Salada Fault is a geological fault between the United States and Mexico. About long, it straddles the Imperial County-California–Baja California border. Earthquakes 1892 According to some seismologists the 1892 Laguna Salada earthquake ranks among the largest earthquakes in California and Baja California in historic times. It occurred on 23 February 1892, and was centered near Laguna Salada in Baja California. 2010 The Laguna Salada Fault is thought to be the origin of the 2010 Baja California earthquake. Prior to this, the fault had not produced a major earthquake for over 100 years, since 1892. Faults The Laguna Salada Fault is a probable southern continuation of the Elsinore Fault Zone in Southern California. These faults are considered to be secondary cohorts of the San Andreas Fault, and as such share some of the strike-slip motion between the North American Plate The North American Plate is a tectonic plate covering most of North America, ... [...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] |
Gulf Of California
The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja California Peninsula from the Mexico, Mexican mainland. It is bordered by the states of Baja California, Baja California Sur, Sonora, and Sinaloa with a coastline of approximately . Rivers that flow into the Gulf of California include the Colorado River, Colorado, Fuerte River, Fuerte, Mayo River (Mexico), Mayo, Sinaloa River, Sinaloa, Sonora River, Sonora, and the Yaqui River, Yaqui. The surface of the gulf is about . Maximum depths exceed because of the complex geology, linked to plate tectonics. The gulf is thought to be one of the most diverse seas on Earth and is home to more than 5,000 species of micro-invertebrates. Parts of the Gulf of California are a UNESCO World Heritage Site. Geography History The marine expeditions of Fortún ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 the floor of the Pacific Ocean. It separates the Pacific Plate to the west from (north to south) the North American Plate, the Rivera Plate, the Cocos Plate, the Nazca Plate, and the Antarctic Plate. It runs south from the Gulf of California in the Salton Sea basin in Southern California to a point near 55° S, 130° W, where it joins the Pacific-Antarctic Ridge trending west-southwest towards Antarctica, near New Zealand (though in some uses the PAR is regarded as the southern section of the EPR). Much of the rise lies about 3200 km (2000 mi) off the South American coast and rises about 1,800–2,700 m (6,000–9,000 ft) above the surrounding seafloor. Overview The oceanic crust is moving away from the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mid-ocean Ridge
A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about and rises about above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a divergent plate boundary. The rate of seafloor spreading determines the morphology of the crest of the mid-ocean ridge and its width in an ocean basin. The production of new seafloor and oceanic lithosphere results from mantle upwelling in response to plate separation. The melt rises as magma at the linear weakness between the separating plates, and emerges as lava, creating new oceanic crust and lithosphere upon cooling. The first discovered mid-ocean ridge was the Mid-Atlantic Ridge, which is a spreading center that bisects the North and South Atlantic basins; hence the origin of the name 'mid-ocean ridge'. Most oceanic spreading centers are not in the middle of their hosting ocean basis but regardless, are traditionally called mid-ocean rid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
