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1971 San Fernando Earthquake
The 1971 San Fernando earthquake (also known as the 1971 Sylmar earthquake) occurred in the early morning of February 9 in the foothills of the San Gabriel Mountains in southern California. The unanticipated thrust earthquake had a magnitude of 6.5 on the scale and 6.6 on the scale, and a maximum Mercalli intensity of XI (''Extreme''). The event was one in a series that affected Los Angeles county in the late 20th century. Damage was locally severe in the northern San Fernando Valley and surface faulting was extensive to the south of the epicenter in the mountains, as well as urban settings along city streets and neighborhoods. Uplift and other effects affected private homes and businesses. The event affected a number of health-care facilities in Sylmar, San Fernando, and other densely populated areas north of central Los Angeles. The Olive View Medical Center and Veterans Hospital both experienced very heavy damage, and buildings collapsed at both sites, causing the majorit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sierra Madre Fault Zone
Situated at the boundary to the San Gabriel Valley and San Fernando Valley, the Sierra Madre Fault Zone (also known as the Sierra Madre-Cucamonga Fault) runs along the southern edge of the San Gabriel Mountains for a total of , where the northwesternmost comprises the San Fernando Fault (the section responsible for the 1971 San Fernando earthquake). A 1980s paleoseismic study that included a trench investigation and mapping revealed that a major earthquake had most likely not occurred to the east of the San Fernando rupture area for at least the last several thousand, and possibly the last 11,000 years. The 1971 event was the first in a series ( 1987 Whittier Narrows, 1991 Sierra Madre, 1994 Northridge) of damaging earthquakes which have occurred on reverse faults in the Los Angeles area. The events triggered discussions concerning the largest magnitude earthquake that could be generated by one of the faults, especially in the Transverse Ranges, but the focal point of earthqua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1933 Long Beach Earthquake
The 1933 Long Beach earthquake took place on March 10 at south of downtown Los Angeles. The epicenter was offshore, southeast of Long Beach, California, on the Newport–Inglewood Fault. The earthquake had a magnitude estimated at 6.4 , and a maximum Mercalli intensity of VIII (''Severe''). Damage to buildings was widespread throughout Southern California. It resulted in 115 to 120 fatalities and an estimated $40 million worth of property damage, equivalent to $ million in . The majority of the fatalities resulted from people running out of buildings exposing themselves to the falling debris. Damage Major damage occurred in the densely populated city of Long Beach on the south-facing coast of Los Angeles County. However, the damage was also found in the industrial area south of downtown Los Angeles. An estimated 75,000 mi3 area was impacted, being felt as far as San Joaquin Valley, Owens Valley, and Northern Baja California. The magnitude of the earthquake is consider ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
North American Plate
The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of , it is the Earth's second largest tectonic plate, behind the Pacific Plate (which borders the plate to the west). 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. The interior of the main continental landmass includes an extensive granitic core called a craton. Along most of the edges of this craton are fragments of crustal material called terranes, which are accreted to the craton by tectonic actions over a long span of time. It is thought that much of North America west of the Rocky Mountains is composed of such terranes. Boundaries The southern boundary with the Cocos Plate to the west and the Caribbean Plate to the east is a transform fault, represented by the Swan Islands Transform F ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleomagnetism
Paleomagnetism (or palaeomagnetismsee ), is the study of magnetic fields recorded in rocks, sediment, or archeological materials. Geophysicists who specialize in paleomagnetism are called ''paleomagnetists.'' Certain magnetic minerals in rocks can record the direction and intensity of Earth's magnetic field at the time they formed. This record provides information on the past behavior of the geomagnetic field and the past location of tectonic plates. The record of geomagnetic reversals preserved in volcanic and sedimentary rock sequences ( magnetostratigraphy) provides a time-scale that is used as a geochronologic tool. Evidence from paleomagnetism led to the revival of the continental drift hypothesis and its transformation into the modern theory of plate tectonics. Apparent polar wander paths provided the first clear geophysical evidence for continental drift, while marine magnetic anomalies did the same for seafloor spreading. Paleomagnetic data continues to extend t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
California Geological Survey
The California Geological Survey, previously known as the California Division of Mines and Geology, is the California state geologic agency. History Although it was not until 1880 that the California State Mining Bureau, predecessor to the California Geological Survey, was established, the "roots" of California's state geological survey date to an earlier time. As might be expected for a state that owed its existence to the gold rush of 1849, the California State Legislature recognized that geologists could provide valuable information. In 1851, one year after California was admitted to the United States, the Legislature named John B. Trask, a medical practitioner and active member of the California Academy of Sciences, as Honorary State Geologist. In 1853 the Legislature passed a joint resolution asking him for geological information about the state. He submitted a report ''On the Geology of the Sierra Nevada, or California Range''. About two months later, the Legislature create ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Strike And Dip
Strike and dip is a measurement convention used to describe the orientation, or attitude, of a planar geologic feature. A feature's strike is the azimuth of an imagined horizontal line across the plane, and its dip is the angle of inclination measured downward from horizontal. They are used together to measure and document a structure's characteristics for study or for use on a geologic map. A feature's orientation can also be represented by dip and dip direction, using the azimuth of the dip rather than the strike value. Linear features are similarly measured with trend and plunge, where "trend" is analogous to dip direction and "plunge" is the dip angle. Strike and dip are measured using a compass and a clinometer. A compass is used to measure the feature's strike by holding the compass horizontally against the feature. A clinometer measures the features dip by recording the inclination perpendicular to the strike. These can be done separately, or together using a tool such ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Little San Bernardino Mountains
The Little San Bernardino Mountains are a short mountain range of the Transverse Ranges, located in southern California in the United States. They extend for approximately southeast from the San Bernardino Mountains through San Bernardino and Riverside Counties to near the northeast edge of the Salton Sink and Salton Sea. The community of Palm Springs looks north and northeast across the Coachella Valley to the range. Geography The range transitions the separation from the Coachella Valley in the Colorado Desert on the south to the Mojave Desert on the north. The peaks vary in height from approximately . The range highpoint is Quail Mountain (California), elevation . Other peaks in the range include Mount Inspiration and Eureka Peak. Habitats Much of the central and eastern parts of the range are within Joshua Tree National Park. Big Morongo Canyon Preserve is located in the western end of the Little San Bernardino Mountains. The oasis here contains one of the ten larg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Channel Islands (California)
The Channel Islands () are an eight-island archipelago located within the Southern California Bight in the Pacific Ocean, off the coast of California. The four Northern Channel Islands are part of the Transverse Ranges geologic province, and the four Southern Channel Islands are part of the Peninsular Ranges province. Five of the islands are within the Channel Islands National Park, and the waters surrounding these islands make up Channel Islands National Marine Sanctuary. The Nature Conservancy was instrumental in establishing the Channel Islands National Marine Sanctuary. The islands were inhabited as early as 13,000 years ago, the earliest paleontological evidence of humans in North America. They are the easternmost islands in the Pacific Island group. The Chumash and Tongva Native Americans who lived later on the islands may be the descendants of the original inhabitants, but they were then displaced by Spaniards who used the islands for fishing and agriculture. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Santa Monica Mountains
The Santa Monica Mountains is a coastal mountain range in Southern California, next to the Pacific Ocean. It is part of the Transverse Ranges. Because of its proximity to densely populated regions, it is one of the most visited natural areas in California. The Santa Monica Mountains National Recreation Area encompasses this mountain range. Geography The range extends approximately east-west from the Hollywood Hills in Los Angeles to Point Mugu in Ventura County. The western mountains, separating the Conejo Valley from Malibu, suddenly end at Mugu Peak as the rugged, nearly impassible shoreline gives way to tidal lagoons and coastal sand dunes of the alluvial Oxnard Plain. The mountain range contributed to the isolation of this vast coastal plain before regular transportation routes reached western Ventura County. The eastern mountains form a barrier between the San Fernando Valley and the Los Angeles Basin, separating "the Valley" on the north and west-central Los Angeles ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Santa Ynez Mountains
The Santa Ynez Mountains are a portion of the Transverse Ranges, part of the Pacific Coast Ranges of the west coast of North America. It is the westernmost range in the Transverse Ranges. The range is a large fault block of Cenozoic age created by the movements of the Santa Ynez Fault. A very narrow range, the Santa Ynez Mountains rise quickly on its north side and drops off equally dramatically along the range's south face along the Gaviota Coast. The Santa Ynez Mountains begin as a series of volcanic hills near Point Arguello, and gradually transitions eastward into a single, well-defined ridge extending from Gaviota Peak to Matilija Creek. The range is approximately contiguous with the Topatopa Mountains beyond to the east, which terminates abruptly at Sespe Creek. The climate of the range is Mediterranean with most of the precipitation falling between November and March. Most of the range lies in the California chaparral and woodlands ecoregion. At the crest and on the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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