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1983 Chagos Archipelago Earthquake
The 1983 Chagos Archipelago earthquake occurred on November 30 at 17:46 UTC (23:46 local time) in the region of the Chagos Archipelago, British Indian Ocean Territory. This earthquake had a moment magnitude and surface wave magnitude of 7.7. This earthquake occurred in the Indian Plate near the Central Indian Ridge. The Central Indian Ridge is unusually active in near-ridge earthquakes. The intense seismic activity in this region may indicate an early stage of converging plate boundary, which is responsible for the N-S extension near Chagos. There was a 40 cm tsunami reported in Victoria, Seychelles Seychelles (, ; ), officially the Republic of Seychelles (french: link=no, République des Seychelles; Creole: ''La Repiblik Sesel''), is an archipelagic state consisting of 115 islands in the Indian Ocean. Its capital and largest city, V .... References External links * {{Earthquakes in 1983 Earthquakes in Asia Chagos Archipelago Earthquake, 1983 Chagos Arch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chagos Archipelago
The Chagos Archipelago () or Chagos Islands (formerly the Bassas de Chagas, and later the Oil Islands) is a group of seven atolls comprising more than 60 islands in the Indian Ocean about 500 kilometres (310 mi) south of the Maldives archipelago. This chain of islands is the southernmost archipelago of the Chagos–Laccadive Ridge, a long submarine mountain range in the Indian Ocean. In its north are the Salomon Islands, Nelson's Island and Peros Banhos; towards its south-west are the Three Brothers, Eagle, Egmont and Danger Island(s); southeast of these is Diego Garcia, by far the largest island. All are low-lying atolls, save for a few extremely small instances, set around lagoons. The Chagos Islands had been home to the native Chagossians, a Bourbonnais Creole-speaking people, until the United Kingdom expelled them from the archipelago at the request of the United States between 1967 and 1973 to allow the United States to build a military base on Diego Garcia. Since 197 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
British Indian Ocean Territory
The British Indian Ocean Territory (BIOT) is an Overseas Territory of the United Kingdom situated in the Indian Ocean, halfway between Tanzania and Indonesia. The territory comprises the seven atolls of the Chagos Archipelago with over 1,000 individual islandsmany very smallamounting to a total land area of . The largest and most southerly island is Diego Garcia, , the site of a Joint Military Facility of the United Kingdom and the United States. The only inhabitants are British and United States military personnel, and associated contractors, who collectively number around 3,000 (2018 figures). The forced removal of Chagossians from the Chagos Archipelago occurred between 1968 and 1973. The Chagossians, then numbering about 2,000 people, were expelled by the UK government to Mauritius and Seychelles in order to construct the military base. Today, the exiled Chagossians are still trying to return, saying that the forced expulsion and dispossession was unlawful, but the ... [...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] |
Surface Wave Magnitude
The surface wave magnitude (M_s) scale is one of the magnitude scales used in seismology to describe the size of an earthquake. It is based on measurements of Rayleigh surface waves that travel along the uppermost layers of the Earth. This magnitude scale is related to the local magnitude scale proposed by Charles Francis Richter in 1935, with modifications from both Richter and Beno Gutenberg throughout the 1940s and 1950s. It is currently used in People's Republic of China as a national standard (GB 17740-1999) for categorising earthquakes. Recorded magnitudes of earthquakes through the mid 20th century, commonly attributed to Richter, could be either M_s or M_L. Definition The formula to calculate surface wave magnitude is: :M_s = \log_\left(\frac\right)_ + \sigma(\Delta)\,, where A is the maximum particle displacement in surface waves (vector sum of the two horizontal displacements) in μm, T is the corresponding period in s (usually 20 2 seconds), Δ is the epi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Seismological Centre
The International Seismological Centre (ISC) is a non-governmental, nonprofit organisation charged with the final collection, definitive analysis and publication of global seismicity. The ISC was formed in 1964 as an international organisation independent of national governments that would carry on the work of the International Seismological Summary in collecting and analyzing seismic data from around the world, and particularly to handle increased flow of data from the World-Wide Standard Seismograph Network (WWSSN), also established that year. The ISC considers its prime task to be the collection and re-analysis of all available earthquake seismic date in order to produce definitive data on earthquakes. The ISC's catalog is considered "the most complete and authoritative final depository of global earthquake parameter data." Purpose The main scientific goal of the Centre is the definitive compilation of earthquake information and the readings on which they are based. Collecti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Indian Plate
The Indian Plate (or India Plate) is a minor tectonic plate straddling the equator in the Eastern Hemisphere. Originally a part of the ancient continent of Gondwana, the Indian Plate broke away from the other fragments of Gondwana , began moving north and carried Insular India with it. It was once fused with the adjacent Australian Plate to form a single Indo-Australian Plate, and recent studies suggest that India and Australia have been separate plates for at least 3 million years and likely longer. The Indian Plate includes most of modern South Asia (the Indian subcontinent) and a portion of the basin under the Indian Ocean, including parts of South China and western Indonesia, and extending up to but not including Ladakh, Kohistan and Balochistan. Plate movements Until roughly , the Indian Plate formed part of the supercontinent Gondwana together with modern Africa, Australia, Antarctica, and South America. Gondwana broke up as these continents drifted apart at different ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Central Indian Ridge
The Central Indian Ridge (CIR) is a north–south-trending mid-ocean ridge in the western Indian Ocean. Geological setting The morphology of the CIR is characteristic of slow to intermediate ridges. The axial valley is 500–1000 m deep; 50–100 km-long ridge segments are separated by 30 km-long transform faults and 10 km-long non-transform discontinuities. Melt supply comes from axial volcanic ridges that are 15 km-long, 1–2 km wide, and reaches 100–200 m above the axial floor. With a spreading rate of 30 mm/yr near the Equator and 49 mm/yr near the Rodrigues Triple Junction (RTJ) at its southern end, the CIR is an intermediately fast spreading ridge characterised by moderate obliquity and few large offsets, the obvious exception being the almost 300 km-long Mary Celeste Fracture Zone at 18°S. Between 21°S and the Mary Celeste Fracture Zone (18°S) the CIR deviates westward. Along this section the larger offsets switc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tsunami
A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explosions (including detonations, landslides, glacier calvings, meteorite impacts and other disturbances) above or below water all have the potential to generate a tsunami. Unlike normal ocean waves, which are generated by wind, or tides, which are in turn generated by the gravitational pull of the Moon and the Sun, a tsunami is generated by the displacement of water from a large event. Tsunami waves do not resemble normal undersea currents or sea waves because their wavelength is far longer. Rather than appearing as a breaking wave, a tsunami may instead initially resemble a rapidly rising tide. For this reason, it is often referred to as a tidal wave, although this usage is not favoured by the scientific community because it might give ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Victoria, Seychelles
Victoria () is the capital and largest city of the Republic of Seychelles, situated on the north-eastern side of Mahé island, the archipelago's main island. The city was first established as the seat of the British colonial government. In 2010, the population of Greater Victoria (including the suburbs) was 26,450 (26.66%) out of the country's total population of 99,202. History The area that would become Victoria was originally settled in 1778 by French colonists after they claimed the island in 1756. The town was called ''L'Établissement'' until 1841 when it was renamed to Victoria by the British, after Queen Victoria. Economy Tourism is an important sector of the economy. The principal exports of Victoria are vanilla, coconuts, coconut oil, fish and guano. Education The Mont Fleuri campus of the University of Seychelles is in Victoria. Culture Attractions in the city include a clocktower modelled on Little Ben in London, the courthouse, the Botanical Gardens, th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seychelles
Seychelles (, ; ), officially the Republic of Seychelles (french: link=no, République des Seychelles; Creole: ''La Repiblik Sesel''), is an archipelagic state consisting of 115 islands in the Indian Ocean. Its capital and largest city, Victoria, is east of mainland Africa. Nearby island countries and territories include the Comoros, Madagascar, Mauritius, and the French overseas departments of Mayotte and Réunion to the south; and Maldives and the Chagos Archipelago (administered by the United Kingdom as the British Indian Ocean Territory) to the east. It is the least populated sovereign African country, with an estimated 2020 population of 98,462. Seychelles was uninhabited prior to being encountered by Europeans in the 16th century. It faced competing French and British interests until coming under full British control in the late 18th century. Since proclaiming independence from the United Kingdom in 1976, it has developed from a largely agricultural society to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earthquakes In Asia
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 ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1983 Earthquakes
The year 1983 saw both the official beginning of the Internet and the first mobile cellular telephone call. Events January * January 1 – The migration of the ARPANET to TCP/IP is officially completed (this is considered to be the beginning of the true Internet). * January 24 – Twenty-five members of the Red Brigades are sentenced to life imprisonment for the 1978 murder of Italian politician Aldo Moro. * January 25 ** High-ranking Nazi war criminal Klaus Barbie is arrested in Bolivia. ** IRAS is launched from Vandenberg AFB, to conduct the world's first all-sky infrared survey from space. February * February 2 – Giovanni Vigliotto goes on trial on charges of polygamy involving 105 women. * February 3 – Prime Minister of Australia Malcolm Fraser is granted a double dissolution of both houses of parliament, for elections on March 5, 1983. As Fraser is being granted the dissolution, Bill Hayden resigns as leader of the Australian Labor Party, and in the subseq ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
