|
1812 Ventura Earthquake
The 1812 Ventura earthquake (also known as the Santa Barbara earthquake) occurred on the morning of December 21 at 11:00 Pacific Standard Time (PST). The 7.2 earthquake was assigned a with a maximum Modified Mercalli intensity of X (''Extreme''). The seismic shaking was followed by a tsunami that considerably damaged places in present-day Santa Barbara and Ventura Counties, California, which was at the time a territory of the Spanish Empire. One person was killed during the earthquake and another from an aftershock. The earthquake occurred while the region was recovering from another event on December 8. Geological setting The San Andreas is the "master fault" of California: it is the main plate boundary in the San Andreas Fault System, which includes several other major active faults. This zone of interaction between the Pacific and North American plates has resulted in hundreds of faults crisscrossing California. There are several strike-slip, reverse, and thrust fau ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alta California
Alta California (, ), also known as Nueva California () among other names, was a province of New Spain formally established in 1804. Along with the Baja California peninsula, it had previously comprised the province of , but was made a separate province in 1804 (named ). Following the Mexican War of Independence, it became a territory of First Mexican Empire, Mexico in April 1822 and was renamed in 1824. The territory included all of the present-day U.S. states of California, Nevada, and Utah, and parts of Arizona, Wyoming, and Colorado. The territory was with Baja California Territory, Baja California (as a single ) in Mexico's 1836 ''Siete Leyes'' (Seven Laws) constitutional reform, granting it more autonomy. That change was undone in 1846, but rendered moot by the outcome of the Mexican–American War in 1848, when most of the areas formerly comprising Alta California Mexican Cession, were ceded to the U.S. in Treaty of Guadalupe Hidalgo, the treaty which ended the war. In ... [...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] |
Dendrochronology
Dendrochronology (or tree-ring dating) is the scientific method of chronological dating, dating tree rings (also called growth rings) to the exact year they were formed in a tree. As well as dating them, this can give data for dendroclimatology, the study of climate and atmospheric conditions during different periods in history from the wood of old trees. Dendrochronology derives from the Ancient Greek (), meaning "tree", (), meaning "time", and (), "the study of". Dendrochronology is useful for determining the precise age of samples, especially those that are too recent for radiocarbon dating, which always produces a range rather than an exact date. However, for a precise date of the death of the tree a full sample to the edge is needed, which most trimmed timber will not provide. It also gives data on the timing of events and rates of change in the environment (most prominently climate) and also in wood found in archaeology or works of art and architecture, such as old pane ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
USGS - San Andreas Fault Zone
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 Public Se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coulomb Stress Transfer
Coulomb stress transfer is a Seismology, seismic-related geology, geological process of Stress (mechanics), stress changes to surrounding material caused by local discrete deformation events. Using mapped displacements of the Earth's surface during earthquakes, the computed Coulomb stress changes suggest that the stress relieved during an earthquake not only dissipates but can also move up and down Fault (geology), fault segments, concentrating and promoting subsequent tremors. Importantly, Coulomb stress changes have been applied to earthquake-forecasting models that have been used to assess potential Seismic hazard, hazards related to earthquake activity. Coulomb stress change The Mohr–Coulomb theory, Coulomb failure criterion requires that the Coulomb stress exceeds a value σf defined by the shear stress τB, normal stress σB, pore pressure p, and coefficient of friction μ of a failure plane, such that It is also often assumed that changes in pore fluid pressure induced b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1978 Santa Barbara Earthquake
The 1978 Santa Barbara earthquake (also known as the Goleta earthquake), occurred on August 13, 1978, 3:54 p.m. ( PDT) with its epicenter beneath the Santa Barbara Channel. The magnitude of the earthquake was estimated at 5.1 according to the Southern California Seismic Network; however, it may have been as high as 5.6 . There were no deaths from the event; however, 65 people sustained mild to moderate injuries. Tectonic setting Santa Barbara is part of California, which is known for its very high level of seismic activity, the second highest in all of the United States only behind Alaska. The Santa Barbara area is affected by numerous faults, inland within the mountainous ridges on the Santa Ynez Range down to the coastal plains and beneath the Santa Barbara Channel. The Santa Barbara Channel lies within the Transverse Ranges block where the transform boundary between the North American and Pacific plates takes on a transpressional character associated with the "Big Ben ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1925 Santa Barbara Earthquake
The 1925 Santa Barbara earthquake hit the area of Santa Barbara, California on June 29, with a moment magnitude between 6.5 and 6.8 and a maximum Mercalli Intensity of IX (''Violent''). It resulted in 13 deaths and destroyed the historic center of the city, with damage estimated at $8 million (about $111 million in 2017). Earthquake Although no foreshocks were reported felt before the mainshock, a pressure gauge recording card at the local waterworks showed disturbances beginning at 3:27 a.m., which were likely caused by foreshocks. At 6:44 a.m. the mainshock occurred which lasted 19 seconds. The epicenter of the earthquake was located in the sea off the coast of Santa Barbara, in the Santa Barbara Channel. The fault on which it occurred appears to have been an extension of the Mesa fault or the Santa Ynez system. The earthquake was felt from Paso Robles ( San Luis Obispo County) to the north to Santa Ana ( Orange County) to the south and to Mojave (Ker ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wrightwood, California
Wrightwood is a census-designated place in San Bernardino County, California. It sits at an elevation of . The population was 4,720 at the 2020 census, up from 4,525 at the 2010 census. Wrightwood is located northeast of Los Angeles. It is on the Pacific Crest Trail. History Located in a pine-covered valley in the San Gabriel Mountains, the Wrightwood area was first developed as cattle ranches in the 19th century by Nathan and Truman Swarthout. Later, the main ranch, owned by Sumner Wright, was broken up into residential and commercial lots, and by the 1920s a community had taken root. Early ski enthusiasts discovered the north-facing slopes of the San Gabriels above the Swarthout Valley. Until 1937, the ski area, originally known as Big Pines, was part of a Los Angeles County park. After World War II, Big Pines opened their 1946–47 ski season with a new chairlift and the Sepp Benedikter Ski School (according to their ad in the February 1947 issue of ''Western Skiing'' ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Garlock Fault
The Garlock Fault is a left-lateral strike-slip fault running northeast–southwest along the north margins of the Mojave Desert of Southern California, for much of its length along the southern base of the Tehachapi Mountains. Geography Stretching for , it is the second-longest fault in California, and one of the most prominent geological features in the southern part of the state. It marks the northern boundary of the area known as the Mojave Block, as well as the southern ends of the Sierra Nevada and the valleys of the westernmost Basin and Range province. The Garlock Fault runs from a junction with the San Andreas Fault in the Antelope Valley, eastward to a junction with the Death Valley Fault Zone in the eastern Mojave Desert. It is named after the historic mining town of Garlock, founded in 1894 by Eugene Garlock and now a ghost town. Relatively few communities lie directly along the Garlock, as it is primarily situated in the desert, with Frazier Park, Tehachapi, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Santa Monica Mountains
The Santa Monica Mountains are a coastal mountain range in Southern California, next to the Pacific Ocean. It is part of the Transverse Ranges. The Santa Monica Mountains National Recreation Area encompasses this mountain range. Because of its proximity to densely populated regions, it is one of the most visited natural areas in California. 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] |
Thrust Fault
A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. If the angle of the fault plane is lower (often less than 15 degrees from the horizontal) and the displacement of the overlying block is large (often in the kilometer range) the fault is called an ''overthrust'' or ''overthrust fault''. Erosion can remove part of the overlying block, creating a ''fenster'' (or ''window'') – when the underlying block is exposed only in a relatively small area. When erosion removes most of the overlying block, leaving island-like remnants resting on the lower block, the remnants are called ''klippen'' (singular '' klippe''). Blind thrust faults If the fault plane terminates before it reaches the Earth's surface, it is called a ''blind thrust'' fault. Because of the lack of surface evidence, blind thrust fa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
