The Shanxi Rift System or Fen–Wei Rift System is a zone of active extensional tectonics that forms the eastern margin of the Ordos Block in northern China. The zone extends for at least 900 km (560 mi) and runs south-southwest to north-northeast. The individual rift basins that make up the rift system have an overall en echelon geometry, consistent with a right lateral sense of strike-slip displacement across the zone. The basins contain a thick sedimentary sequence of Neogene age, which ranges from 2.0 to 3.8 km (1.2 to 2.4 mi) in thickness. The rift system is continuous with the Weihe Basin to the southwest, which became active during the Paleogene . Rupture of the major normal faults that bound the Weihe and Shanxi rift basins has caused many large and damaging historical earthquakes, including the 1303 Hongdong (>200,000 deaths), 1556 Shaanxi (830,000 deaths), 1626 Lingqiu (>5,200 deaths), 1695 Linfen (>52,600 deaths) and 1815 Pinglu (>13,000 deaths) events.
31-793: The Shanxi Rift System is named for the province of Shanxi as that defines the extent of the rift zone, apart from the Weihe Basin, which is in Shaanxi province. The combined Weihe and Shanxi rift systems are sometimes referred to as the Weihe-Shanxi Rift System. The alternative name, the Fen-Wei Rift System, derives from the Fen and the Wei Rivers which drain through most of the rift zone. The rift system runs for over 900 km (560 mi) between
62-610: A half-graben geometry and is bounded to the southeast by the Wutaishan Fault. It has a maximum sedimentary infill of about 1,800 m of Pliocene to recent age. Subsidence in the Datong Basin is controlled by the SW–NE trending, SE-dipping Kouquan Fault and the WSW–ENE trending, NNW-dipping Liulengshan Piedmont and Hengshan Piedmont faults. Other smaller basins form part of the northern sector of
93-614: A mainly half-graben geometry, thickening southwards into the large normal faults that form the boundary on its southern side with the mountains of the Qinling orogenic belt. The two main faults are the North Qinling Fault, which runs from the western end of the basin to just beyond Xi'an . To the east the main basin-bounding fault steps to the north in the form of the Huashan Fault, which continues eastward to near Lingbao , where it forms
124-550: A serious problem. Because of the rise of population and the development of economy, the industrial, domestic, and other kinds of pollution have been on the rise. Great quantities of sewage are indiscriminately discharged into the riverbed downstream of the No. 1 and 2 reservoirs. However, the government is trying to fix the problem. 35°15′47″N 110°23′28″E / 35.263°N 110.391°E / 35.263; 110.391 Coulomb stress transfer Coulomb stress transfer
155-480: A similar history with the Weihe Basin, containing a thick sequence of continental clastic sedimentary rocks, with the oldest part of the succession being of Eocene age. Despite their similarities the two basins appear to have remained separate until at least the late Pliocene, when they were connected by the Yellow River . This SW–NE trending basin is a strongly asymmetric half-graben with southeastward thickening into
186-630: Is 120 km (75 mi) long and 20 to 30 km (12 to 19 mi) wide, with a maximum fill of about 4 km (2.5 mi). It is continuous with the Weihe Basin to the west. Tectonically it is bound to the south by the Sanmenxia-Lingbao Fault, which links to the eastern segment of the Huashan Fault, and to the north by a fault along the southern edge of the Zhongtiao range, the South Zhongtiaoshan Fault. The Sanmenxia Basin shares
217-668: Is 148 km (92 mi)m in length and about 42 km (26 mi) in width, with a total area of 6,200 km (2,400 sq mi). It is bounded to the northwest by the Jiaocheng Fault and the southeast by the Taigu Fault. It is markedly asymmetric with a maximum thickness developed against the Jiaocheng Fault to the northwest of about 3.8 km (2.4 mi), with a sedimentary fill ranging in age from Pliocene to recent. The thickness in this basin reduces to less than 1 km (0.62 mi) on its southeastern edge. Also known as
248-682: 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. The Coulomb failure criterion requires that
279-678: Is the Fen River valley, it had led to the Yellow River . The second valley is the Su River, which was along the north edge of Zhongtiao Mountain; and it was forming another triangular basin. The Fen River valley offered different routes of communication in Wei River valley, that both routes were open to the either side of the Yellow River . Modern cities on or near the Fen from north to south are: Taiyuan , Linfen , Houma , Hejin . Fenyang , although named after
310-483: Is the biggest artificial reservoir in Shanxi province; it is also the scenic spot in the province. The length from south to north is 15 kilometers, the width is 5 kilometers, the total area is 32 square kilometers, and the capacity of reservoir is 720 million cubic meters. In 2000, the No. 2 Fen River Reservoir was built about 50 kilometers downstream the No. 1 Fen River Reservoir. The pollution of Fen River reservoir has become
341-706: Is the longest in Shanxi. It is also the second-longest tributary of the Yellow River . Within Taiyuan , the Fen runs from north to south; the prefecture includes one-seventh of the river's course. The Fen is usually identified with the Ji River said by Sima Qian and others to have flowed beside the home of the Yellow Emperor . The Discourses of the States states that the Ji was the home of
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#1733085456942372-515: The 1990s, the municipal government of Taiyuan built artificial and removable structures across the river at different locations to create reservoirs of water for landscaping purposes. The surface area of these reservoirs amounts to 1.7 million square meters and, along with newly created vegetation of 1.3 million square meters on the banks, forms the 6-kilometer long Fen River Park . The vegetation consist of 183 species trees, shrubs and other green plants. The No. 1 Fen River reservoir, built in 1960,
403-582: The Anatolian fault system had witnessed ten earthquakes of M6.6 or greater. The evolution of the Coulomb stress changes along the North Anatolian fault as a result of these earthquakes showed that 11 of the 13 ruptures occurred in areas of increased Coulomb stress caused by a previous rupture. This method has been also used to predict seismicity around active volcanoes submitted to significant variation of stress in
434-468: The Coulomb stress exceeds a value σ f defined by the shear stress τ B , normal stress σ B , 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 effects are incorporated into an effective coefficient of friction μ’, such that This simplification allows for
465-584: The Paleogene the basin initiated as a result of NW–SE directed extension. After a brief period of NE–SW directed extension in the Pleistocene, the current tectonic setting, NNW–SSE directed extension began. GPS data are unable to constrain current displacement rates. The Sanmenxia Basin trends WSW–ENE and lies between the Qinling orogenic belt to the south and the Zhongtiao Mountains to the north. The basin
496-616: The Qinling orogenic belt in the south to the Yinshan-Yanshan orogenic belt in the north, varying in width from 40 to 120 km (25 to 75 mi). It has an overall S-shaped geometry, trending WSW–ENE to SW-NE at its southern and northern ends and trending SSW–NNE in the main part of the rift system. The main individual rift basins that make up the rift system, from south to north, are the Weihe, Sanmenxia, Yuncheng, Linfen, Taiyuan, Xinding and Datong basins. The west–east trending Weihe Basin has
527-713: The Xinzhou–Dingxian Basin, this SW–NE trending half-graben has its main faulted boundary on its southeastern margin as the Xizhoushan Fault against the Xizhouan range. The sedimentary fill of this basin reaches a maximum of about 1.8 km (1.1 mi). In some descriptions of the Shanxi Rift System, this basin name has been used to cover three sub-basins, the Dingxiang, Yuanping and Daixian. The Daixian sub-basin has
558-511: The Yellow Emperor's clan before he fought the clan of Yandi (the "Flame Emperor"). Its name is identical with the surname of the royal family under the Zhou . Pulleyblank argues, however, that the supposed "Ji River" could be a later invention as "there seems to be no record of a Ji River outside the myth" of the Yellow Emperor. The lower Fen was part of the core area of ancient China and held
589-588: The Yuncheng Basin, from which it is separated by the E'mei highlands. It has the opposite polarity, that is the boundary fault that controls the half-graben, the Louyunshan Fault, in this case lies on the northwest side of the basin, against the Luoyunshan range. The maximum thickness of the upper Miocene to recent sedimentary fill is in the range 1.8 to 2.2 km (1.1 to 1.4 mi). This SW–NE trending basin
620-799: The calculation of Coulomb stress changes on a fault plane to be independent of the regional stress field but instead depends on the fault geometry, sense of slip, and coefficient of friction. The significance of the Coulomb stress changes was discovered when mapped displacements of neighbouring fault movements were used to calculate Coulomb stress changes along faults. Results revealed that the stress relieved on faults during earthquakes did not simply dissipate, but also moved up and down fault segments. Moreover, mapped lobes of increased and decreased Coulomb stress around local faults exhibited increased and decreased rates of seismicity respectively shortly after neighboring earthquakes, but eventually return to their background rate over time. Stress triggering describes
651-462: The capital of the state of Jin near Houma . The river nurtured the 2500-year-old Sanjin Civilization and has since been called the "Mother River of People" in Shanxi . In Taiyuan , the Fen River valley area has fertile water resource; for this reason, the Fen area has become the economic center of Shanxi province. There are two valleys of the south region of further south. One of the valleys
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#1733085456942682-631: The center of Shanxi Province , China . It originates in the Guancen Mountains of Ningwu County in northeast Shanxi, flows southeast into the basin of Taiyuan , and then south through the central valley of Shanxi before turning west to join the Yellow River west of Hejin . The Fen and the Wei Rivers are the two largest tributaries of the Yellow River. The river is 694 kilometers (431 mi) long and drains an area of 39,417 km (15,219 sq mi), 25.3% of Shanxi's area. The Fen River
713-527: The large normal fault along the northwestern side of the Zhongtiao range, the North Zhongtiaoshan Fault. It contains a maximum thickness of over 5 km (3.1 mi) of sedimentary rocks, which extend back in age to the Late Miocene. The sequence thins northwards to a few hundred metres, with pre-Cenozoic basement rock locally exposed in the E'mei highlands. The Linfen Basin lies to the north of
744-518: The magma chamber. Although no official Coulomb stress transfer prediction model is being used by government agencies, geologic surveys often analyze earthquake threats using Coulomb stress theory. As an example, the last of the previous thirteen earthquakes along Turkey's North Anatolian Fault , near the town of Duzce, was successfully predicted by local geologists before the rupture occurred. This allowed for engineers to evacuate unstable structures and limit significant damage. Scientists estimate that
775-419: The responsive rupturing of faults from increases in Coulomb stress caused by exogenous deformation events. Although neighboring displacements often yield small magnitude stress changes, areas of disturbed Coulomb stress states have been successfully used to explain the spatial distribution of stress triggered aftershock seismicity . On June 28, 1992, a M7.3 earthquake that struck near Landers, California
806-982: The rift system south and east of the Datong Basin. These include the Yangyuan Basin (controlled by the Liulengshan Fault), the Hunyuan Basin (controlled by the Hengshan Fault), the Yu-Guang Basin (controlled by the South Yu-Guang Basin Fault) and the Lingqiu Basin (controlled by the Taibaiweishan Fault), all of which have a half-graben geometry. The rift system is one of the most seismically active areas in northern China. There have been many major (M>6) earthquakes with epicentres in or close to
837-403: The rift system, with 16 such events since 1300. The sequence of large earthquakes has been explained as mainly a result of modification of the stress field by each earthquake. Modelling of stress changes starting with the 1303 Hongdong earthquake, have estimated that three-quarters of M≥6.5 events in the rift system occurred in areas of stress increase. Fen River The Fen River drains
868-423: The river, is actually some 20-plus km to the west of it. As with any river that flows through a city, the Fen River added extra charm to the city of Taiyuan . The construction of dams upstream, however, reduced the once-abundant flow of the river to a mere trickle, and the river bed went dry. From 1949, Chinese government built the reservoirs such as Fen River, Wenyu River, Hui River, and several other reservoirs on
899-552: The southern boundary to the Sanmenxia Basin. The maximum thickness of Cenozoic sedimentary fill in the basin is estimated to be in the range 4 to 6 km (2.5 to 3.7 mi). The oldest unit is thought to be of Late Eocene age, dating the onset of rifting in this basin to the Eocene. The sequence consists of continental clastic sedimentary rocks , deposited in alluvial , fluvial and lacustrine sedimentary environments . During
930-450: The tributaries of the Fen River, which ensured Taiyuan city and other cities’ industrial water, and enlarged Taiyuan basin and Linfen basin's irrigation. Before the 1950s, Fen River valley's flood areas is 13.34 ten thousand hectares, saline-alkali soil is 6.67 ten thousand hectares. Today, due to the influence of the water conservancy facilities, the water logging is almost inexistence, huge areas of saline-alkali soil are reformed. In
961-717: Was followed (about three hours later) by the M6.5 Big Bear foreshock earthquake 40 km away. Calculated Coulomb stress changes from both of these earthquakes showed a westward lobe of 2.1–2.9 bars of increased Coulomb stress to have resulted from the displacement associated with both earthquakes. Of the roughly 20,000 aftershocks that occurred 25 days after June 28 within a 5 km radius, more than 75% occurred in areas where Coulomb stress had increased and less than 25% occurred in areas where Coulomb stress had dropped. Another successful case study of earthquake prediction occurred along Turkey's North Anatolian fault system. From 1939 to 1999,