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What is earth quake and why its occurs An earthquake (also known as a quake, tremor or temblor) is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time. Earthquakes are measured using observations from seismometers. The moment magnitude is the most common scale on which earthquakes larger than approximately 5 are reported for the entire globe. tectonic plates on Earth. Tectonic plates are pieces of the Earth's crust and uppermost mantle, together referred to as thelithosphere. Understanding how and where hydrothermal vents and other high-energy phenomena occur on the seafloor requires a closer look at the Earth's structure and the forces at work deep within the planet. The Earth's inner coreis a solid sphere composed mostly of iron. It is about 2,400 kilometers (1,500 mi) in diameter and is believed to be as hot as 6650 C (12000 F). This heat is probably generated by the radioactive decay of uranium and other elements. The inner core is bordered by aliquid outer core that is 4700 C (8500F). Surrounding the outer core is the mantle,which is composed of hot, molten rock called magma. The churning of the magma, caused by the heat rising from the core, generates pressure on the Earth's surface layer, or crust. The crust is very thin compared to the other layers, ranging in thickness from only about 3.2 kilometers (2 mi) in some areas of the ocean floor to some 121 kilometers (75 mi) deep under mountains. The crust is composed of plates on which the continents and oceans rest. Like giant rafts, these plates move slowly on the magma beneath them. The plates may move apart, collide, and slide past each other, resulting in such high-energy phenomena as hydrothermal vents, volcanoes, and earthquakes.
How Plates Move on the Earth Powered by forces originating in Earths radioactive, solid iron inner core, these tectonic plates move ponderously about at varying speeds and in different directions atop a layer of much hotter, softer, more malleable rock called the athenosphere. Because of the high temperatures and immense pressures found here, the uppermost part of the athenosphere is deformed and flows almost plastically just beneath the Earths surface. This characteristic of the athenosphere to flow allows the plates to inch along on their endless journeys around the surface of the earth, moving no faster than human fingernails grow.
One idea that might explain the ability of the athenosphere to flow is the idea of convection currents. When mantle rocks near the radioactive core are heated, they become less dense than the cooler, upper mantle rocks. These warmer rocks rise while the cooler rocks sink, creating slow, vertical currents within the mantle (these convection currents move mantle rocks only a few centimeters a year). This movement of warmer and cooler mantle rocks, in turn, creates pockets of circulation within the mantle called convection cells. The circulation of these convection cells could very well be the driving force behind the movement of tectonic plates over the athenosphere.
Movement of plates in the world
China geography and locationChina is Located in Southeast Asia along the coastline of the Pacific Ocean, China is the world's third largest country, after Russia and Canada. With an area of 9.6 million square kilometers and a coastline of 18,000 kilometers, its shape on the map is like a rooster. It reaches Mohe in Heilongjiang Province as its northern end, Zengmu Ansha (or James Shoal) to the south, Pamirs to the west, and expands to the eastern border at the conjunction of the Heilongjiang (Amur) River and the Wusuli (Ussuri) River, spanning about 50 degrees of latitude and 62 degrees of longitude. China is bordered by 14 countries -- Korea, Vietnam, Laos, Burma, India, Bhutan, Nepal, Pakistan, Afghanistan, Tajikistan, Kyrgyzstan, Kazakstan, Mongolia, and Russia. Marine-side neighbors include eight countries -- North Korea, Korea, Japan, Philippines, Brunei, Indonesia, Malaysia and Vietnam. China stretches some 5,026 kilometers (3,123 mi) across the East Asian landmass bordering the East China Sea, Korea Bay, Yellow Sea, and South China Sea, between North Korea and Vietnam in a changing configuration of broad plains, expansive deserts, and loftymountain ranges, including vast areas of inhospitable terrain. The eastern half of the country, its seacoast fringed with offshore islands, is a region of fertile lowlands, foothills and mountains, deserts, steppes, and subtropical areas. The western half of China is a region of sunken basins, rolling plateaus, and towering massifs, including a portion of the highest tableland on earth.
Introduction of earthquakes in china hina is principally a part of the Eurasian plate, but the margins of the Indian and Philippine Sea plates are involved in the Himalayas and in the Coastal Range of Taiwan, respectively. Within the
Eurasian plate, the Cathaysian paleoplate is separated from the Angaraian paleoplate by the Junggar-Hegen suture, which contains Paleozoic ophiolites and rare blueschists. The three microplates of the Cathaysian paleoplate consist of Precambrian cratons and/or Phanerozoic accretionary fold belts. These coalesced Precambrian cratons record at least six stages of intense orogeny before cratonization. The Paleozoic to Cenozoic accretionary fold belts of China can be correlated with similar events now found in west Pacific-, Andean-, and Atlantictype active continental margins. Ophiolites occupying many of these tectonic zones provide evidence for the age and igneous history of oceanic crust formed during the Paleozoic to Cenozoic. The presence of blueschist in some of these Chinese sutures reveals evidence of large-scale subduction and tectonic exhumation during consolidation of the Eurasian plate. Cenozoic collision of the Eurasian and Indian plates produced deformation and uplift of the Himalayas, strongly influencing the tectonics of western China. In contrast, MesozoicTertiaryevolution of eastern China is typical basin-range geology, similar to that of the western United States, which included development of deep sedimentary basins along with calc-alkaline plutonic and volcanic activity associated with crustal thinning and high heat flow. The complicated tectonic evolution of China is greatly illuminated by the presence of ophiolites and blueschists in Proterozoic to Tertiary convergent boundaries. These petrotectonic assemblages provide evidence of an extremely mobile history of plate movement in China.
Movement of plates in china region
Collision of India with the Asian mainland during the earliest Eocene (~50 Ma) has resulted in the growth of the world's largest orogenic belt, the Himalayas, and the associated Tibetan plateau. The seimotectonic tectonic evolution of China is characterized by the merger of several microcontinents throughout the entire Phanerozoic.
The collision and associated convergence and extension has created 64 major tectonic zones in China, which can be subdivided into a smaller number of tectonic "regions"
Seismic plates of china region
Thus, China is located in one of the most active seismic regions of the world that has been plagued by numerous destructive earthquakes during its long history. The most significant of the historical earthquakes, in terms of lives lost, was that which occurred in 1556. However, since 1900 China has experienced several more destructive earthquakes. The most destructive earthquakes of the 20th Century were those of 1927 in Tsinghai, of 1932 in Gansu, of 1933 in Sichuan, of 1969 in Bohai Sea, of 1970 in Tonghai (Yunnan), of 1974 in Zhaotong (Yunnan), of 1975 in Haicheng, and of 1976 in Tangshan (Hebei Province) . The more recent earthquake of May 12, 2008 in Sichuan Province was the latest of the more destructive earthquakes that have struck China in the new millennium. The following is a brief account of the 1556 event and of some of the more destructive earthquakes since 1900
Epicenters of historical earthquakes in China 900 A.D to 2000
China's Seismic ZonesCollision of India with the Asian mainland during the earliest Eocene (~50 Ma) has resulted in the growth of the world's largest orogenic belt, the Himalayas, and the associated Tibetan plateau. The seimotectonic tectonic evolution of China is characterized by the merger of several microcontinents throughout the entire Phanerozoic (e.g. Zhang et al., 1984; Hendrix and Davis, 2001).The collision and associated convergence and extension has created 64 major tectonic zones in China, which can be subdivided into a smaller number of tectonic "regions" (Zhang et al.,1984; Yin and Nie,1996. The eartquake (with a magnitude reported in the literature as ranging from 7.5 to 8.0), struck at 3:42 a.m. in the early morning hours of July 28, the worst time when the city was asleep. What made matters worse, was the fact that this city is located in the center of an area with major crustal faults on four sides and most structures had been built on unstable, alluvial soils. Only a few of its structures were earthquake-resistant. The earthquake, with its epicenter right on Tangshan, broke a five-mile section of a 25-mile long fault that passes through the city. Along the west side of this fault the land moved five feet northward in relation to the land on the east side. The east block tipped downward at the northern end of the break and upward toward the south end.
List of earthquake in china
Date September 27, 1290 September 25, 1303
Event 1290 Chihli earthquake 1303 Shanxi earthquake
Epicenter 41.5N 119.3ENingcheng County No data Shanxi, China 34.50N 109.30E Shaanxi, China