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1867 Keelung Earthquake
The 1867 Keelung earthquake occurred off the northern coast of Taiwan on the morning of December 18 with a magnitude of 7.0. It produced strong shaking that seriously damaged the cities of Keelung and Taipei. A tsunami, thought to be the only confirmed destructive of its kind in Taiwan, drowned hundreds and had a run-up exceeding . The total death toll was estimated to be 580 while more than 100 were injured. It was followed by aftershocks that were felt on average ten times a day. Tectonic setting Taiwan is situated on a complex convergent boundary between the Eurasian Plate and the Philippine Sea Plate. Off the northeastern coast of the island, the Philippine Sea Plate Subduction, subducts northwards beneath the Ryukyu Islands (on the overriding Eurasian Plate) along the Ryukyu Trench. To the south of the island, oceanic crust of the Eurasian Plate subducts beneath eastwards the Philippine Sea Plate along the Manila Trench. Taiwan lies at the junction of the two subduction zon ... [...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 wikt:accelerogram, 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 magnitude scale, Richter and Moment magnitude scale, moment magnitude scales, it is not a measure of the total seismic scales#Magnitude and intensity, energy (magnitude, or size) of an earthquake, but rather of how hard the earth shake ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Continental Collision
In geology, continental collision is a phenomenon of plate tectonics that occurs at convergent boundaries. Continental collision is a variation on the fundamental process of subduction, whereby the subduction zone is destroyed, mountains produced, and two continents sutured together. Continental collision is only known to occur on Earth. Continental collision is not an instantaneous event, but may take several tens of millions of years before the faulting and folding caused by collisions stops. The collision between India and Asia has been going on for about 50 million years already and shows no signs of abating. Collision between East and West Gondwana to form the East African Orogen took about 100 million years from beginning (610 Ma) to end (510 Ma). The collision between Gondwana and Laurasia to form Pangea occurred in a relatively brief interval, about 50 million years long. Subduction zone: the collision site The process begins as two conti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epicenter
The epicenter, epicentre () or epicentrum in seismology is the point on the Earth's surface directly above a hypocenter or focus, the point where an earthquake or an underground explosion originates. Surface damage Before the instrumental period of earthquake observation, the epicenter was thought to be the location where the greatest damage occurred, but the subsurface fault rupture may be long and spread surface damage across the entire rupture zone. As an example, in the magnitude 7.9 Denali earthquake of 2002 in Alaska, the epicenter was at the western end of the rupture, but the greatest damage was about away at the eastern end. Focal depths of earthquakes occurring in continental crust mostly range from . Continental earthquakes below are rare whereas in subduction zone earthquakes can originate at depths deeper than . Epicentral distance During an earthquake, seismic waves propagate in all directions from the hypocenter. Seismic shadowing occurs on the opposite s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seismic Intensity Scales
Seismic intensity scales categorize the intensity or severity of ground shaking (quaking) at a given location, such as resulting from an earthquake. They are distinguished from seismic magnitude scales, which measure the magnitude or overall strength of an earthquake, which may, or perhaps may not, cause perceptible shaking. Intensity scales are based on the observed effects of the shaking, such as the degree to which people or animals were alarmed, and the extent and severity of damage to different kinds of structures or natural features. The maximal intensity observed, and the extent of the area where shaking was felt (see isoseismal map, below), can be used to estimate the location and magnitude of the source earthquake; this is especially useful for historical earthquakes where there is no instrumental record. Ground shaking Ground shaking can be caused in various ways (volcanic tremors, avalanches, large explosions, etc.), but shaking intense enough to cause damage is usuall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quaternary
The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ago to the present. The Quaternary Period is divided into two epochs: the Pleistocene (2.58 million years ago to 11.7 thousand years ago) and the Holocene (11.7 thousand years ago to today, although a third epoch, the Anthropocene, has been proposed but is not yet officially recognised by the ICS). The Quaternary Period is typically defined by the cyclic growth and decay of continental ice sheets related to the Milankovitch cycles and the associated climate and environmental changes that they caused. Research history In 1759 Giovanni Arduino proposed that the geological strata of northern Italy could be divided into four successive formations or "orders" ( it, quattro ordini). The term "quaternary" was introduced by Jules Desnoye ... [...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 a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jinshan District, New Taipei
Jinshan District () is a rural district on the coast in northern New Taipei, Taiwan. The district draws many visitors each year because of its hot springs and its proximity to Chin Pao San and the Ju Ming Museum. The district is home to the Dharma Drum Buddhist College, an institution of higher learning founded by Dharma Drum Mountain monastics devoted to the principles of Zen Buddhism. Name Origin This area was originally a Ketagalan people, Ketagalan settlement, called "Ki-ppare" (Basay language, Basay: Quimourije), meaning "bumper harvest". This was later adapted as ''Kimpauli'' (金包里; ), the choice of characters perhaps influenced by the discovery of golden dust in the Sulfur creeks. In 1920 during Taiwan under Japanese rule, Japanese rule, the area was renamed Kanayama Village (金山庄), Kīrun District (基隆郡), Taihoku Prefecture. Qingshui Wetland Adjacent to Jinshan town at the north-west is a lowland wetland formed by alluvial deposits from Sulphur Creek ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Normal Fault
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] |
American Geophysical Union
The American Geophysical Union (AGU) is a 501(c)(3) nonprofit organization of Earth, atmospheric, ocean, hydrologic, space, and planetary scientists and enthusiasts that according to their website includes 130,000 people (not members). AGU's activities are focused on the organization and dissemination of scientific information in the interdisciplinary and international fields within the Earth and space sciences. The geophysical sciences involve four fundamental areas: atmospheric and ocean sciences; solid-Earth sciences; hydrologic sciences; and space sciences. The organization's headquarters is located on Florida Avenue in Washington, D.C. History The AGU was established in December 1919 by the National Research Council (NRC) to represent the United States in the International Union of Geodesy and Geophysics (IUGG), and its first chairman was William Bowie of the United States Coast and Geodetic Survey (USCGS). For more than 50 years, it operated as an unincorporated affili ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tatun Volcano Group
Tatun Volcanoes (), a group of volcanoes located in northern Taiwan, is located 15 km north of Taipei, and lies to the west of Keelung. It just adjoins the northern coast of the Taiwan island. The volcano group was a result of episodic volcanism between 2.8 and 0.2 Ma. As of 2005, some geothermal activity was occurring and gas fumaroles were active among these volcanoes. Observations on Tatun Volcano Group suggest that magma chambers probably still exist under the land surface of northern Taiwan. History The north of the island is where evidence of volcanic activity is most obvious. In the early 20th century, the North Range of hills, also called ''Daitonzan'' from Japanese or ''Twa-tun'' from Hokkien, was recognized as having an abundance of sulfur deposits. There were three craters in the North Range between Tamsui and Kimpauli (approx. modern-day Jinshan). The North hill crater, over in diameter and about deep, was the most extensive and was sometimes filled with water ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Submarine Landslide
Submarine landslides are marine landslides that transport sediment across the continental shelf and into the deep ocean. A submarine landslide is initiated when the downwards driving stress (gravity and other factors) exceeds the resisting stress of the seafloor slope material, causing movements along one or more concave to planar rupture surfaces. Submarine landslides take place in a variety of different settings, including planes as low as 1°, and can cause significant damage to both life and property. Recent advances have been made in understanding the nature and processes of submarine landslides through the use of sidescan sonar and other seafloor mapping technology.Hampton, M & Locat, J (1996) Submarine landslides. Reviews of Geophysics, 34, 33–59.Locat, J & Lee, HJ (2002) Submarine landslides: Advances and challenges. Canadian Geotechnical Journal, 39, 193.Mason, D, Habitz, C, Wynn, R, Pederson, G & Lovholt, F (2006) Submarine landslides: processes, triggers and hazar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Richter Magnitude Scale
The Richter scale —also called the Richter magnitude scale, Richter's magnitude scale, and the Gutenberg–Richter scale—is a measure of the strength of earthquakes, developed by Charles Francis Richter and presented in his landmark 1935 paper, where he called it the "magnitude scale". This was later revised and renamed the local magnitude scale, denoted as ML or . Because of various shortcomings of the original scale, most seismological authorities now use other similar scales such as the moment magnitude scale () to report earthquake magnitudes, but much of the news media still erroneously refers to these as "Richter" magnitudes. All magnitude scales retain the logarithmic character of the original and are scaled to have roughly comparable numeric values (typically in the middle of the scale). Due to the variance in earthquakes, it is essential to understand the Richter scale uses logarithms simply to make the measurements manageable (i.e., a magnitude 3 quake factors ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
