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1994 Northridge Earthquake
The 1994 Northridge earthquake affected Greater Los Angeles, California, on January 17, 1994, at 04:30:55 PST. The epicenter of the moment 6.7 () blind thrust earthquake was beneath the San Fernando Valley. Lasting approximately 8 seconds and achieving the largest peak ground acceleration of over 1.7 ''g'', it was the largest earthquake in the area since 1971. Shaking was felt as far away as San Diego, Turlock, Las Vegas, Richfield, Phoenix, and Ensenada. Fifty-seven people died and more than 9,000 were injured. In addition, property damage was estimated to be $13–50 billion, making it among the costliest natural disasters in U.S. history. Geology The epicenter region of the earthquake was located in the San Fernando Valley, about northwest of downtown Los Angeles. The United States Geological Survey (USGS) placed the hypocenter's geographical coordinates at and at a depth of . Measuring 6.7, it was the largest earthquake recorded in the Los Angeles area sin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
United States Geological Survey
The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on March 3, 1879, to study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The agency also makes maps of planets and moons, based on data from U.S. space probes. The sole scientific agency of the U.S. Department of the Interior, USGS is a fact-finding research organization with no regulatory responsibility. It is headquartered in Reston, Virginia, with major offices near Lakewood, Colorado; at the Denver Federal Center; and in NASA Research Park in California. In 2009, it employed about 8,670 people. The current motto of the USGS, in use since August 1997, is "science for a changing world". The agency's previous slogan, adopted on its hundredth anniversary, was "Earth Science in the Pub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phoenix, Arizona
Phoenix ( ) is the List of capitals in the United States, capital and List of cities and towns in Arizona#List of cities and towns, most populous city of the U.S. state of Arizona. With over 1.6 million residents at the 2020 census, it is the List of United States cities by population, fifth-most populous city in the United States and the List of capitals in the United States, most populous state capital in the country. Phoenix is the most populous city of the Phoenix metropolitan area, also known as the Valley of the Sun, which in turn is part of the Salt River Valley and Arizona Sun Corridor. The metro area is the Metropolitan statistical area, 10th-largest by population in the United States with approximately 4.95 million people , making it the most populous in the Southwestern United States. Phoenix, the seat of Maricopa County, Arizona, Maricopa County, is the largest city by population and area in Arizona, with an area of , and is also the List of United States cities by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Santa Clara River Valley
The Santa Clara River Valley is a rural, mainly agricultural valley in Ventura County, California Ventura County () is a County (United States), county located in Southern California, the southern part of the U.S. state of California. As of the 2020 United States census, 2020 census, the population was 843,843. The largest city is Oxnard, Ca ... that has been given the moniker Heritage Valley by the namesake tourism bureau. The valley includes the communities of Santa Paula, California, Santa Paula, Fillmore, California, Fillmore, Piru, California, Piru and the national historic landmark of Rancho Camulos. Named for the Santa Clara River (California), Santa Clara River, which winds through the valley before emptying into the Pacific Ocean between the cities of Ventura, California, Ventura and Oxnard, California, Oxnard, the tourist bureau describes it as "Southern California's last pristine agricultural valley nestled along the banks of the free-flowing Santa Clara River." Geo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Landslide
Landslides, also known as landslips, rockslips or rockslides, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, mudflows, shallow or deep-seated slope failures and debris flows. Landslides occur in a variety of environments, characterized by either steep or gentle slope gradients, from mountain ranges to coastal cliffs or even underwater, in which case they are called submarine landslides. Gravity is the primary driving force for a landslide to occur, but there are other factors affecting slope stability that produce specific conditions that make a slope prone to failure. In many cases, the landslide is triggered by a specific event (such as heavy rainfall, an earthquake, a slope cut to build a road, and many others), although this is not always identifiable. Landslides are frequently made worse by human development (such as urban sprawl) and resource exploitation (such as mining and deforestation). Land degradation freque ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oat Mountain (California)
Oat Mountain is a peak of the Santa Susana Mountains overlooking the San Fernando Valley (near Los Angeles, California) to the south and southeast. Oat Mountain is the highest peak in the Santa Susana Mountains of California. The Los Angeles district of Chatsworth is to the south of the mountain. There are many microwave relay antennas as well as Doppler weather equipment at Oat Mountain. SoCal Gas has several wells in the area as well. Climate The weather on Oat Mountain varies from season to season. In January, occasional rain showers and thunderstorms may pass over the mountain. Colder storms produce light snow on the peaks of the mountain, when the snow level drops below 4,000 feet. In spring, the weather may change. Some years it may be very dry, affecting the vegetation. In other years, spring could bring heavy storms with upwards of 4" of rain and some snow. The summer is dry, with occasional thunderstorms (brought in by sub-tropical moisture in the Pacific Ocean) from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tectonic Uplift
Tectonic uplift is the orogeny, geologic uplift of Earth#Surface, Earth's surface that is attributed to plate tectonics. While Isostasy, isostatic response is important, an increase in the mean elevation of a region can only occur in response to tectonic processes of Thrust tectonics, crustal thickening (such as Mountain formation, mountain building events), changes in the density distribution of the crust and underlying Mantle (geology), mantle, and flexural support due to the bending of rigid lithosphere. Tectonic uplift results in denudation (processes that wear away the earth's surface) by raising buried rocks closer to the surface. This process can redistribute large loads from an elevated region to a topographically lower area as well – thus promoting an isostatic response in the region of denudation (which can cause local bedrock uplift). The timing, magnitude, and rate of denudation can be estimated by geologists using pressure-temperature studies. Crustal thickening C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Santa Susana Mountains
The Santa Susana Mountains are a transverse range of mountains in Southern California, north of the city of Los Angeles, in the United States. The range runs east-west, separating the San Fernando and Simi valleys on its south from the Santa Clara River Valley to the north and the Santa Clarita Valley to the northeast. The Oxnard Plain is to the west of the Santa Susana Mountains. Description Geography The Newhall Pass separates the Santa Susana Mountains from the San Gabriel Mountains to the east. Newhall Pass is the major north-south connection between the San Fernando and Santa Clarita valleys, and Interstate 5 and a railroad line share Newhall Pass. The Santa Susana Pass (containing SR 118) connects the Simi and San Fernando valleys, and separates the Santa Susana Mountains from the Simi Hills to the south. Santa Susana Pass State Historic Park is located in the Simi Hills, just south of the Santa Susana Pass, at the northwestern edge of the San Fernando Valley. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anticline
In structural geology, an anticline is a type of Fold (geology), fold that is an arch-like shape and has its oldest Bed (geology), beds at its core, whereas a syncline is the inverse of an anticline. A typical anticline is convex curve, convex up in which the hinge or crest is the location where the curvature is greatest, and the limbs are the sides of the fold that Strike and dip, dip away from the hinge. Anticlines can be recognized and differentiated from antiforms by a sequence of rock layers that become progressively older toward the center of the fold. Therefore, if age relationships between various Stratum, rock strata are unknown, the term antiform should be used. The progressing age of the rock strata towards the core and uplifted center, are the trademark indications for evidence of anticlines on a geological map. These formations occur because anticlinal ridges typically develop above thrust faults during crustal deformations. The uplifted core of the fold cau ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mainshock
In seismology, the mainshock is the largest earthquake in a sequence, sometimes preceded by one or more foreshocks, and almost always followed by many aftershocks. Foreshock A foreshock is an earthquake that occurs before a larger seismic event (the mainshock) and is related to it in both time and space. The designation of an earthquake as ''foreshock'', ''mainshock'' or aftershock is only possible after the full sequence of events has happened. Aftershock In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in the same area of the main shock, caused as the displaced crust adjusts to the effects of the main shock. Large earthquakes can have hundreds to thousands of instrumentally detectable aftershocks, which steadily decrease in magnitude and frequency according to known laws. In some earthquakes the main rupture happens in two or more steps, resulting in multiple main shocks. These are known as doublet earthquakes Doublet is a word de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aftershock
In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in Epicenter, the same area of the Mainshock, main shock, caused as the displaced Crust (geology), crust adjusts to the effects of the main shock. Large earthquakes can have hundreds to thousands of instrumentally detectable aftershocks, which steadily decrease in magnitude and frequency according to #Aftershock size and frequency with time, a consistent pattern. In some earthquakes the main rupture happens in two or more steps, resulting in multiple main shocks. These are known as doublet earthquakes, and in general can be distinguished from aftershocks in having similar magnitudes and nearly identical seismic waveforms. Distribution of aftershocks Most aftershocks are located over the full area of fault rupture and either occur along the fault plane itself or along other faults within the volume affected by the strain associated with the main shock. Typically, aftershocks are found up to a d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fault Stepover
Strike-slip tectonics or wrench tectonics is a type of tectonics that is dominated by lateral (horizontal) movements within the Crust (geology), Earth's crust (and lithosphere). Where a zone of strike-slip tectonics forms the boundary between two Plate tectonics, tectonic plates, this is known as a transform fault, transform or conservative plate boundary. Areas of strike-slip tectonics are characterised by particular deformation styles including: ''stepovers'', ''Riedel shears'', ''flower structures'' and ''strike-slip duplexes''. Where the displacement along a zone of strike-slip deviates from parallelism with the zone itself, the style becomes either transpressional or transtensional depending on the sense of deviation. Strike-slip tectonics is characteristic of several geological environments, including oceanic and continental transform faults, zones of oblique collision and the deforming foreland of zones of continental collision. Deformation styles Stepovers When strike-sl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earthquake Rupture
In seismology, an earthquake rupture is the extent of slip that occurs during an earthquake in the Earth's crust. Earthquakes occur for many reasons that include: landslides, movement of magma in a volcano, the formation of a new fault, or, most commonly of all, a slip on an existing fault. Nucleation A tectonic earthquake begins by an initial rupture at a point on the fault surface, a process known as nucleation. The scale of the nucleation zone is uncertain, with some evidence, such as the rupture dimensions of the smallest earthquakes, suggesting that it is smaller than 100 m while other evidence, such as a slow component revealed by low-frequency spectra of some earthquakes, suggest that it is larger. The possibility that the nucleation involves some sort of preparation process is supported by the observation that about 40% of earthquakes are preceded by foreshocks. However, some large earthquakes, such as the M8.6 1950 India – China earthquake., have no foreshocks and it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
