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1923 Renda Earthquake
The 1923 Renda earthquake occurred on March 24 at 20:40 local time between the counties of Daofu and Luhuo in Sichuan, China. The estimated 7.0–7.3 earthquake was assigned a maximum modified Mercalli intensity scale rating of X (''Extreme''). Severe damage occurred in Sichuan, killing an estimated 4,800 people. Tectonic setting Western Sichuan is situated at the edge of the Tibetan Plateau in a vast zone of complex continental deformation caused by the collision of the Indian Plate with the Eurasian Plate. As the thrusting of the Indian Plate beneath the Eurasian Plate along the Himalayas continues, the continental crust within the Eurasian Plate is actively uplifted and thickened, forming the Tibetan Plateau. As there are no active thrust structures within the plateau, compression is accommodated by strike-slip motion along large structures including the Altyn Tagh Fault, Kunlun Fault, Haiyuan Fault and Xianshuihe fault system. Left-lateral strike-slip motion squeezes th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time In China
The time in China follows a single standard time offset of UTC+08:00 (eight hours ahead of Coordinated Universal Time), even though the country spans almost five geographical time zones. The official national standard time is called ''Beijing Time'' (BJT, ) domestically and ''China Standard Time'' (CST) internationally. Daylight saving time has not been observed since 1991. China Standard Time (UTC+8) is consistent across Mainland China, Hong Kong, Macau, Taiwan, Philippines, Singapore, Brunei, Mongolia, etc. History In the 1870s, the Shanghai Xujiahui Observatory was constructed by a French Catholic missionary. In 1880s officials in Shanghai French Concession started to provide a time announcement service using the Shanghai Mean Solar Time provided by the aforementioned observatory for ships into and out of Shanghai. By the end of 19th century, the time standard provided by the observatory had been switched to GMT+08:00. The practice has spread to other coastal ports, and in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extensional Tectonics
Extensional tectonics is concerned with the structures formed by, and the tectonic processes associated with, the stretching of a planetary body's crust or lithosphere. Deformation styles The types of structure and the geometries formed depend on the amount of stretching involved. Stretching is generally measured using the parameter ''β'', known as the ''beta factor'', where : \beta = \frac \,, ''t''0 is the initial crustal thickness and ''t''1 is the final crustal thickness. It is also the equivalent of the strain parameter ''stretch''. Low beta factor In areas of relatively low crustal stretching, the dominant structures are high to moderate angle normal faults, with associated half grabens and tilted fault blocks. High beta factor In areas of high crustal stretching, individual extensional faults may become rotated to too low a dip to remain active and a new set of faults may be generated. Large displacements may juxtapose syntectonic sediments against metamorphic roc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rockfall
A rockfall or rock-fallWhittow, John (1984). ''Dictionary of Physical Geography''. London: Penguin, 1984. . is a quantity/sheets of rock that has fallen freely from a cliff face. The term is also used for collapse of rock from roof or walls of mine or quarry workings. "A rockfall is a fragment of rock (a block) detached by sliding, toppling, or falling, that falls along a vertical or sub-vertical cliff, proceeds down slope by bouncing and flying along ballistic trajectories or by rolling on talus or debris slopes." Alternatively, a "rockfall is the natural downward motion of a detached block or series of blocks with a small volume involving free falling, bouncing, rolling, and sliding". The mode of failure differs from that of a rockslide. Causal mechanisms Favourable geology and climate are the principal causal mechanisms of rockfall, factors that include intact condition of the rock mass, discontinuities within the rockmass, weathering susceptibility, ground and surface water, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kangding
Kangding (), also called Tachienlu and Dartsedo (; ), is a county-level city and the seat of Garzê Tibetan Autonomous Prefecture in Sichuan province of Southwest China. Kangding is on the bank of the Dadu River and has been considered the historical border between the Kham region of Tibet and the Sichuan region. Kangding's urban center is called Lucheng, which has around 134,000 inhabitants. Names Historically, the urban center was known by Chinese as Dajianlu (written also as Tachienlu or Tatsienlu) from the Chinese transliteration of the Tibetan name Dartsedo or Darzêdo. History Kangding was on the historical border between Tibet and the rest of China, from Kangding to the west lies Tibetan civilization where as to the east Han cultural areas; It was the capital of the Kingdom of Chakla. During its history, Kangding has witnessed many conflicts between Tibetan and Han polities. Kangding was for many centuries an important trading city where Han brick tea was carried by por ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fissure
A fissure is a long, narrow crack opening along the surface of Earth. The term is derived from the Latin word , which means 'cleft' or 'crack'. Fissures emerge in Earth's crust, on ice sheets and glaciers, and on volcanoes. Ground fissure A , also called an , is a long, narrow crack or linear opening in the Earth's crust. Ground fissures can form naturally, such as from tectonic faulting and earthquakes, or as a consequence of human activity, such as oil mining and groundwater pumping. Once formed, ground fissures can be extended and eroded by torrential rain. They can be hazardous to people and livestock living on the affected surfaces and damaging to property and infrastructure, such as roads, underground pipes, canals, and dams. In circumstances where there is the extensive withdrawal of groundwater, the earth above the water table can subside causing fissures to form at the surface. This typically occurs at the floor of arid valleys having rock formations and compacte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Landslide
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 grade (slope), 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 She ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Avalanche
An avalanche is a rapid flow of snow down a slope, such as a hill or mountain. Avalanches can be set off spontaneously, by such factors as increased precipitation or snowpack weakening, or by external means such as humans, animals, and earthquakes. Primarily composed of flowing snow and air, large avalanches have the capability to capture and move ice, rocks, and trees. Avalanches occur in two general forms, or combinations thereof: slab avalanches made of tightly packed snow, triggered by a collapse of an underlying weak snow layer, and loose snow avalanches made of looser snow. After being set off, avalanches usually accelerate rapidly and grow in mass and volume as they capture more snow. If an avalanche moves fast enough, some of the snow may mix with the air, forming a powder snow avalanche. Though they appear to share similarities, avalanches are distinct from slush flows, mudslides, rock slides, and serac collapses. They are also different from large scale movement ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Defensive Wall
A defensive wall is a fortification usually used to protect a city, town or other settlement from potential aggressors. The walls can range from simple palisades or earthworks to extensive military fortifications with towers, bastions and gates for access to the city. From ancient to modern times, they were used to enclose settlements. Generally, these are referred to as city walls or town walls, although there were also walls, such as the Great Wall of China, Walls of Benin, Hadrian's Wall, Anastasian Wall, and the Atlantic Wall, which extended far beyond the borders of a city and were used to enclose regions or mark territorial boundaries. In mountainous terrain, defensive walls such as ''letzis'' were used in combination with castles to seal valleys from potential attack. Beyond their defensive utility, many walls also had important symbolic functions representing the status and independence of the communities they embraced. Existing ancient walls are almost always masonry ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coulomb Stress Transfer
Coulomb stress transfer is a seismic-related geological process of stress changes to surrounding material caused by local discrete deformation events. Using mapped displacements of the Earth's surface during earthquakes, the computed Coulomb stress changes suggest that the stress relieved during an earthquake not only dissipates but can also move up and down fault segments, concentrating and promoting subsequent tremors. Importantly, Coulomb stress changes have been applied to earthquake-forecasting models that have been used to assess potential hazards related to earthquake activity. Coulomb stress change The Coulomb failure criterion requires that the Coulomb stress exceeds a value σf defined by the shear stress τB, normal stress σB, pore pressure p, and coefficient of friction μ of a failure plane, such that It is also often assumed that changes in pore fluid pressure induced by changes in stress are proportional to the normal stress change across the fault plane. These ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1981 Dawu Earthquake
The 1981 Dawu earthquake occurred on , in Sichuan, China. Registering a surface wave magnitude of 6.8, the earthquake killed about 150 people and injured roughly 300 more. It caused comprehensive damage within close range of its epicenter. Background China has an extensive history of catastrophic earthquakes that ranges back to 1290. The first verified earthquake took place in Chih-li, killing roughly 100,000 people. The next great earthquake was probably the 1556 Shaanxi earthquake, the most devastating earthquake of all time. Roughly 830,000 were killed by the event. Other earthquakes in 1917, 1918, 1920, 1923, 1925, 1927, 1931, 1932, 1933, 1948, 1950, 1966, 1969, 1970, 1974, 1975, 1976 each killed at least one thousand people. Since 1981, earthquake fatalities have diminished greatly, though have not been stopped. As recently as 2008, an earthquake in Sichuan killed nearly 90,000 people. Characteristics The epicenter was pinpointed to Dawu County in Sichuan. Its offici ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1973 Luhuo Earthquake
The 1973 Luhuo earthquake struck near the town of Zhaggo in the Garzê Tibetan Autonomous Prefecture of Sichuan Province, China on February 6 with a magnitude of 7.6 . The earthquake had a maximum intensity of X (''Extreme'') on the Mercalli intensity scale, resulting in 2,199 deaths and a further 2,743 injuries in Sichuan. Serious and widespread destruction to villages was reported in Luhuo County as a result of the earthquake. Tectonic setting Western Sichuan is situated at the edge of the Tibetan Plateau in a vast zone of complex continental deformation caused by the collision of the Indian Plate with the Eurasian Plate. As the thrusting of the Indian Plate beneath the Eurasian Plate along the Himalayas continues, the continental crust within the Eurasian Plate is actively uplifted and thickened, forming the Tibetan Plateau. As there are no active thrust structures within the plateau, compression is accommodated by strike-slip motion along large structures including the Altyn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meizoseismal Area
The meizoseismal area in an earthquake is the area of maximum damage. For example, in the Charleston, South Carolina, earthquake of 1886, the meizoseismal area was an area about twenty by thirty miles stretching northeast between Charleston and Jedburg and incorporating Summerville. The estimated epicenter was near Middleton Place Middleton Place is a plantation in Dorchester County, along the banks of the Ashley River west of the Ashley and about northwest of downtown Charleston, in the U.S. state of South Carolina. Built in several phases during the 18th and 19th cent .... References Seismology {{seismology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
