|
Supershear Earthquake
In seismology, a supershear earthquake is an earthquake in which the propagation of the rupture along the fault surface occurs at speeds in excess of the seismic shear wave (S-wave) velocity. This causes an effect analogous to a sonic boom. Rupture propagation velocity During seismic events along a fault surface the displacement initiates at the focus and then propagates outwards. Typically for large earthquakes the focus lies towards one end of the slip surface and much of the propagation is unidirectional (e.g. the 2008 Sichuan and 2004 Indian Ocean earthquakes). Theoretical studies have in the past suggested that the upper bound for propagation velocity is that of Rayleigh waves, approximately 0.92 of the shear wave velocity. However, evidence of propagation at velocities between S-wave and compressional wave (P-wave) values have been reported for several earthquakesArchuleta,R.J. 1984A faulting model for the 1979 Imperial Valley earthquake J. Geophys. Res., 89, 4559–4585. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seismology
Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies. It also includes studies of earthquake environmental effects such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, glacial, fluvial, oceanic, atmospheric, and artificial processes such as explosions. A related field that uses geology to infer information regarding past earthquakes is paleoseismology. A recording of Earth motion as a function of time is called a seismogram. A seismologist is a scientist who does research in seismology. History Scholarly interest in earthquakes can be traced back to antiquity. Early speculations on the natural causes of earthquakes were included in the writings of Thales of Miletus (c. 585 BCE), Anaximenes of Miletus (c. 550 BCE), Aristotle (c. 340 BCE), and Zha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moment Magnitude Scale
The moment magnitude scale (MMS; denoted explicitly with or Mw, and generally implied with use of a single M for magnitude) is a measure of an earthquake's magnitude ("size" or strength) based on its seismic moment. It was defined in a 1979 paper by Thomas C. Hanks and Hiroo Kanamori. Similar to the local magnitude scale, local magnitude/Richter scale () defined by Charles Francis Richter in 1935, it uses a logarithmic scale; small earthquakes have approximately the same magnitudes on both scales. Despite the difference, news media often says "Richter scale" when referring to the moment magnitude scale. Moment magnitude () is considered the authoritative magnitude scale for ranking earthquakes by size. It is more directly related to the energy of an earthquake than other scales, and does not saturate—that is, it does not underestimate magnitudes as other scales do in certain conditions. It has become the standard scale used by seismological authorities like the U.S. Geological ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2014 Aegean Sea Earthquake
An earthquake occurred in the northern Aegean Sea between Greece and Turkey on May 24, 2014. It had a moment magnitude of 6.9 and a maximum Mercalli intensity scale, Mercalli intensity of VIII (''Severe''). Serious damage was reported on the Turkish island of Imbros and the cities of Edirne and Çanakkale, as well as on the Greek island of Lemnos. The earthquake was felt in Bulgaria and southern Romania. Several aftershocks followed the main shock, the strongest measuring 5.3 ML. This aftershock struck the Gulf of Saros at 12:31 local time. Tectonic setting The northern part of the Aegean Sea shows a transition from the strike-slip tectonics associated with the North Anatolian Fault (NAF) to the extensional tectonics that characterise the area north of the Hellenic arc. The location of this earthquake is on the westward continuation of the NAF on the boundary between the Anatolian Plate and the Eurasian Plate. Other earthquakes on this part of the NAF include an M6.6 event in 19 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Queen Charlotte Fault
The Queen Charlotte Fault is an active transform fault that marks the boundary of the North American plate and the Pacific plate. It is Canada's right-lateral strike-slip equivalent to the San Andreas Fault to the south in California. The Queen Charlotte Fault forms a triple junction south with the Cascadia subduction zone and the Explorer Ridge (the Queen Charlotte Triple Junction). The Queen Charlotte Fault (QCF) forms a transpressional plate boundary, and is as active as other major transform fault systems (i.e. San Andreas, Alpine) in terms of slip rates and seismogenic potential. It sustains the highest known deformation rates among continental or continent-ocean transform systems globally, accommodating greater than 50mm/yr dextral offset. The entire approximately 900 km offshore length has ruptured in seven greater than magnitude 7 events during the last century, making the cumulative historical seismic moment release higher than any other modern transform plate bound ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2013 Craig, Alaska Earthquake
The 2013 Craig, Alaska earthquake (also known as the Queen Charlotte Fault earthquake) struck on January 5, at 12:58 am ( UTC–7) near the city of Craig and Hydaburg, on Prince of Wales Island. The 7.5 earthquake came nearly three months after an 7.8 quake struck Haida Gwaii on October 28, in 2012. The quake prompted a regional tsunami warning to British Columbia and Alaska, but it was later cancelled. Due to the remote location of the quake, there were no reports of casualties or damages. Tectonic setting The Queen Charlotte Fault is a major right-lateral (dextral) strike-slip and transform fault running off the coast of British Columbia and into Southern Alaska, through the Saint Elias Range for more than 700 miles. Its southernmost section joins a spreading ridge of the Gorda Plate and the Cascadia subduction zone while the northern termination section joins the a thrust fault where the Yakutat terrane plows into the North American Plate. It has been the source of seve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2012 Indian Ocean Earthquakes
The 2012 Indian Ocean earthquakes were magnitude 8.6 and 8.2 undersea earthquakes that struck near the Indonesian province of Aceh on 11 April at 15:38 local time. Initially, authorities feared that the initial earthquake would cause a tsunami and warnings were issued across the Indian Ocean; however, these warnings were subsequently cancelled. These were unusually strong intraplate earthquakes and the largest strike-slip earthquake ever recorded. Tectonic setting The 2012 earthquake's epicenter was located within the Indo-Australian Plate, which is divided into two sub- or proto-plates: the Indian, and Australian. At their boundary, the Indian and Australian Plates converge at per year in a NNW–SSE direction. This convergence is accommodated by a broad zone of diffuse deformation. As part of that intraplate deformation, north–south trending fracture zones have been reactivated from the Ninety East Ridge as far east as 97°E. The Indo–Australian Plate was formed afte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xianshuihe Fault System
The Xianshuihe fault system is a major active sinistral (left-lateral) strike-slip fault zone in southwestern China, at the eastern edge of the Tibetan Plateau. It has been responsible for many major earthquakes, and is one of the most seismically active fault zones in this part of China. Tectonic setting The Xianshuihe fault system lies within the complex zone of continental collision between the Indian Plate and the Eurasian Plate. It forms one of a set of sinistral fault zones that help accommodate the eastward spreading of the Tibetan Plateau. The fault zone defines the northern and eastern edges of the Sichuan-Yunnan block, and the southeastern boundary of the Bayan Har block. Geometry The Xianshuihe fault system comprises several distinct segments, with an overall length of about 350 km. The main segments are the Ganzi (or Ganzi-Yushu), the Xianshuihe, the Anninghe-Zemuhe, and the Xiaojiang faults. Seismicity Movements on this fault system have been responsible for man ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2010 Yushu Earthquake
The 2010 Yushu earthquake struck on April 14 and registered a magnitude of 6.9 Mw (USGS, EMSC) or 7.1 MsAbout 400 dead, 10,000 injured in 7.1-magnitude quake in China's Qinghai , xinhuanet.com. Retrieved 14 April 2010. ( CEA, CENC). It had a maximum felt intensity of IX (''Violent'') on the . It originated in [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Denali Fault
The Denali Fault is a major intracontinental dextral (right lateral) strike-slip fault in western North America, extending from northwestern British Columbia, Canada to the central region of the U.S. state of Alaska. Location The Denali Fault is located in Alaska's Denali National Park and to the east. This National Park includes part of a massive mountain range more than 600 miles long. Along the Denali Fault, lateral and vertical offset movement is taking place. The steep north face of Denali, known as the Wickersham Wall, rises 15,000 feet from its base, and is a result of this relatively recent movement. Effects Alaska's network of faults is a result of tectonic activity; the Pacific Plate is actively subducting (sliding under) the North American Plate, and the Denali Fault is located on the boundary between the two plates. The fault's rate of displacement varies from 1 mm to 35 mm per year. It was the main fault along which the 2002 Denali earthquake occu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2002 Denali Earthquake
The 2002 Denali earthquake occurred at 22:12:41 UTC (1:12 PM Local Time) November 3 with an epicenter 66 km ESE of Denali National Park, Alaska, United States. This 7.9 Mw earthquake was the largest recorded in the United States in 37 years (after the 1965 Rat Islands earthquake). The shock was the strongest ever recorded in the interior of Alaska. Due to the remote location, there were no fatalities and only one injury. Due to the shallow depth, it was felt at least as far away as Seattle and it generated seiches on bodies of water as far away as Texas and New Orleans, Louisiana. About 20 houseboats were damaged by a seiche on a lake in Washington State. Tectonic setting The Denali-Totschunda fault is a major dextral (right lateral) strike-slip system, similar in scale to the San Andreas fault system. In Alaska, moving from east to west, the plate interactions change from a transform boundary between Pacific and North American plates to a collision zone with a microplat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2001 Kunlun Earthquake
The 2001 Kunlun earthquake also known as the 2001 Kokoxili earthquake, occurred on 14 November 2001 at 09:26 UTC (17:26 local time), with an epicenter near Kokoxili, close to the border between Qinghai and Xinjiang in a remote mountainous region. With a magnitude of 7.8 Mw (8.0 ), it was the most powerful earthquake in China for 5 decades. No casualties were reported, presumably due to the very low population density and the lack of high-rise buildings. This earthquake was associated with the longest surface rupture ever recorded on land, ~450 km. Tectonic setting The Kunlun fault is one of the major sinistral strike-slip structures that accommodate the eastward motion of the Tibetan Plateau relative to the Eurasian Plate. This motion is caused by the lateral spreading of the zone of thickened crust associated with the collision between the Indian and Eurasian Plates. Earthquake The earthquake rupture began on a relatively small strike-slip fault segment at the west ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
