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Seismic Hazard
A seismic hazard is the probability that an earthquake will occur in a given geographic area, within a given window of time, and with ground motion intensity exceeding a given threshold. With a hazard thus estimated, risk can be assessed and included in such areas as building codes for standard buildings, designing larger buildings and infrastructure projects, land use planning and determining insurance rates. The seismic hazard studies also may generate two standard measures of anticipated ground motion, both confusingly abbreviated MCE; the simpler probabilistic Maximum Considered Earthquake (or Event ), used in standard building codes, and the more detailed and deterministic Maximum Credible Earthquake incorporated in the design of larger buildings and civil infrastructure like dams or bridges. It is important to clarify which MCE is being discussed. Calculations for determining seismic hazard were first formulated by C. Allin Cornell in 1968 and, depending on their l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earthquake
An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from those that are so weak that they cannot be felt, to those violent enough to propel objects and people into the air, damage critical infrastructure, and wreak destruction across entire cities. The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time period. The seismicity at a particular location in the Earth is the average rate of seismic energy release per unit volume. The word ''tremor'' is also used for non-earthquake seismic rumbling. At the Earth's surface, earthquakes manifest themselves by shaking and displacing or disrupting the ground. When the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently to cause a tsunami. Earthquakes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peak Ground Acceleration
Peak ground acceleration (PGA) is equal to the maximum ground acceleration that occurred during earthquake shaking at a location. PGA is equal to the amplitude of the largest absolute acceleration recorded on an accelerogram at a site during a particular earthquake. Earthquake shaking generally occurs in all three directions. Therefore, PGA is often split into the horizontal and vertical components. Horizontal PGAs are generally larger than those in the vertical direction but this is not always true, especially close to large earthquakes. PGA is an important parameter (also known as an intensity measure) for earthquake engineering, The design basis earthquake ground motion (DBEGM) is often defined in terms of PGA. Unlike the Richter and moment magnitude scales, it is not a measure of the total energy (magnitude, or size) of an earthquake, but rather of how hard the earth shakes at a given geographic point. The Mercalli intensity scale uses personal reports and observations to mea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metre Per Second Squared
The metre per second squared is the unit of acceleration in the International System of Units (SI). As a derived unit, it is composed from the SI base units of length, the metre, and time, the second. Its symbol is written in several forms as m/s2, m·s−2 or ms−2, , or less commonly, as m/s/s. As acceleration, the unit is interpreted physically as change in velocity or speed per time interval, i.e. metre per second per second and is treated as a vector quantity. Example An object experiences a constant acceleration of one metre per second squared (1 m/s2) from a state of rest, then it achieves the speed of 5 m/s after 5 seconds and 10 m/s after 10 seconds. The average acceleration ''a'' can be calculated by dividing the speed ''v'' (m/s) by the time ''t'' (s), so the average acceleration in the first example would be calculated: a = \frac = \frac = 1\text = 1\text^2. Related units Newton's second law states that force equals mass multiplied by acceleration. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Probability Of Exceedance
The frequency of exceedance, sometimes called the annual rate of exceedance, is the frequency with which a random process exceeds some critical value. Typically, the critical value is far from the mean. It is usually defined in terms of the number of peaks of the random process that are outside the boundary. It has applications related to predicting extreme events, such as major earthquakes and floods. Definition The frequency of exceedance is the number of times a stochastic process exceeds some critical value, usually a critical value far from the process' mean, per unit time. Counting exceedance of the critical value can be accomplished either by counting peaks of the process that exceed the critical value or by counting upcrossings of the critical value, where an ''upcrossing'' is an event where the instantaneous value of the process crosses the critical value with positive slope. This article assumes the two methods of counting exceedance are equivalent and that the process ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
USGS
The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization's work spans the disciplines of biology, geography, geology, and hydrology. The USGS is a fact-finding research organization with no regulatory responsibility. The agency was founded on March 3, 1879. The USGS is a bureau of the United States Department of the Interior; it is that department's sole scientific agency. The USGS employs approximately 8,670 people and is headquartered in Reston, Virginia. The USGS also has major offices near Lakewood, Colorado, at the Denver Federal Center, and Menlo Park, California. The current motto of the USGS, in use since August 1997, is "science for a changing world". The agency's previous slogan, adopted on the occasion of its hundredth an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2014 Pga2pct50yrs (vector)
Fourteen or 14 may refer to: * 14 (number), the natural number following 13 and preceding 15 * one of the years 14 BC, AD 14, 1914, 2014 Music * 14th (band), a British electronic music duo * ''14'' (David Garrett album), 2013 *''14'', an unreleased album by Charli XCX * "14" (song), 2007, from ''Courage'' by Paula Cole Other uses * ''Fourteen'' (film), a 2019 American film directed by Dan Sallitt * ''Fourteen'' (play), a 1919 play by Alice Gerstenberg * ''Fourteen'' (manga), a 1990 manga series by Kazuo Umezu * ''14'' (novel), a 2013 science fiction novel by Peter Clines * ''The 14'', a 1973 British drama film directed by David Hemmings * Fourteen, West Virginia, United States, an unincorporated community * Lot Fourteen, redevelopment site in Adelaide, South Australia, previously occupied by the Royal Adelaide Hospital * "The Fourteen", a nickname for NASA Astronaut Group 3 * Fourteen Words, a phrase used by white supremacists and Nazis See also * 1/4 (other) * F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
United States Bureau Of Reclamation
The Bureau of Reclamation, and formerly the United States Reclamation Service, is a federal agency under the U.S. Department of the Interior, which oversees water resource management, specifically as it applies to the oversight and operation of the diversion, delivery, and storage projects that it has built throughout the western United States for irrigation, water supply, and attendant hydroelectric power generation. Currently the Bureau of Reclamation is the largest wholesaler of water in the country, bringing water to more than 31 million people, and providing one in five Western farmers with irrigation water for 10 million acres of farmland, which produce 60% of the nation's vegetables and 25% of its fruits and nuts. The Bureau of Reclamation is also the second largest producer of hydroelectric power in the western United States. On June 17, 1902, in accordance with the Reclamation Act, Secretary of the Interior Ethan Allen Hitchcock established the U.S. Reclamatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anchorage, Alaska
Anchorage () is the largest city in the U.S. state of Alaska by population. With a population of 291,247 in 2020, it contains nearly 40% of the state's population. The Anchorage metropolitan area, which includes Anchorage and the neighboring Matanuska-Susitna Borough, had a population of 398,328 in 2020, accounting for more than half the state's population. At of land area, the city is the fourth-largest by area in the United States and larger than the smallest state, Rhode Island, which has . Anchorage is in Southcentral Alaska, at the terminus of the Cook Inlet, on a peninsula formed by the Knik Arm to the north and the Turnagain Arm to the south. In September 1975, the City of Anchorage merged with the Greater Anchorage Area Borough, creating the Municipality of Anchorage. The municipal city limits span , encompassing the urban core, a joint military base, several outlying communities, and almost all of Chugach State Park. Because of this, less than 10% of the Munic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Good Friday Earthquake
The 1964 Alaskan earthquake, also known as the Great Alaskan earthquake and Good Friday earthquake, occurred at 5:36 PM AKST on Good Friday, March 27.US Geological Survey report on the earthquake Across south-central , ground fissures, collapsing structures, and s resulting from the earthquake caused about 131 deaths. Lasting four minutes and thirty-eight seconds, the magnitude 9.2 |
Landslides
Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated slope failures, mudflows, 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 a heavy rainfall, an earthquake, a slope cut to build a road, and many others), although this is not always identifiable. Causes Landslides occur when the slope (or a portion of it) undergoes some processes that change its condition from stable to unstable. This is essentially due to a decrease in the shear strength o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Soil Liquefaction
Soil liquefaction occurs when a cohesionless saturated or partially saturated soil substantially loses Shear strength (soil), strength and stiffness in response to an applied Shear stress, stress such as shaking during an earthquake or other sudden change in stress condition, in which material that is ordinarily a solid behaves like a liquid. In soil mechanics, the term "liquefied" was first used by Allen Hazen in reference to the 1918 failure of the Calaveras Dam in California. He described the mechanism of flow liquefaction of the embankment dam as: The phenomenon is most often observed in saturated, loose (low density or uncompacted), sandy soils. This is because a loose sand has a tendency to Compressibility, compress when a force, load is applied. Dense sands, by contrast, tend to expand in volume or 'Reynolds' dilatancy, dilate'. If the soil is saturated by water, a condition that often exists when the soil is below the water table or sea level, then water fills the ga ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Characteristic Earthquake
Earthquake prediction is a branch of the science of seismology concerned with the specification of the time, location, and magnitude of future earthquakes within stated limits, and particularly "the determination of parameters for the ''next'' strong earthquake to occur in a region". Earthquake prediction is sometimes distinguished from ''earthquake forecasting'', which can be defined as the probabilistic assessment of ''general'' earthquake hazard, including the frequency and magnitude of damaging earthquakes in a given area over years or decades. Not all scientists distinguish "prediction" and "forecast", but the distinction is useful. Prediction can be further distinguished from earthquake warning systems, which upon detection of an earthquake, provide a real-time warning of seconds to neighboring regions that might be affected. In the 1970s, scientists were optimistic that a practical method for predicting earthquakes would soon be found, but by the 1990s continuing failu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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