This paper made a numerical simulation to the basic tectonic stress field of Chinese mainland and its neighboringregion using the visco-elasticity finite element model and the new published displacement rate result. M...This paper made a numerical simulation to the basic tectonic stress field of Chinese mainland and its neighboringregion using the visco-elasticity finite element model and the new published displacement rate result. Main contents include the simulation of maximum shear stress and its varying rate, the maximum shear strain and its varyingrate, the shear strain energy density and its varying rate. In view of the high inhomogeneous distribution characterof seismicity in space and time in Chinese mainland and its neighboring area, the normalized background energyvalue was given by means of normalized treatment to the earthquake energy release in the eastern and westernparts of Chinese mainland. And the comparison of the simulation result with the actual seismicity was made. Thefesults show that the simulation values can explain well the earthquake distribution character of Chinese mainlandand its neighboring area.展开更多
On the basis of a 3-dimension visco-elastic finite element model of lithosphere in North China, we numerically simulate the recent mutative figures of tectonic stress field. Annual change characteristics of stress fie...On the basis of a 3-dimension visco-elastic finite element model of lithosphere in North China, we numerically simulate the recent mutative figures of tectonic stress field. Annual change characteristics of stress field are: 1 ) Maximum principal tensile stress is about 3 -9 kPaa-1 and its azimuth lie in NNW-SSE. 2) Maximum principal compressive stress is about 1 - 6 kPaa-1 and its azimuth lie in NEE-SWW. 3 ) Maximum principal tensile stress is higher both in the west region and Liaoning Province. 4) Variation of tectonic stress field benefits fault movement in the west part and northeast part of North China. 5 )Annual accumulative rates of Coulomb fracture stress in Tanlu fault belt have segmentation patterns: Jiashan-Guangji segment is the high- est (6 kPaa - 1 ) , Anshan-Liaodongwan segment is the second (5 kPaa - l ) , and others are relatively lower ( 3 - 4 kPaa-1 ).展开更多
According to the earthquake focal mechanism solutions of 55 moderately strong earthquakes onthe northeastern side of Pamirs,the spatial and temporal distribution of earthquakes ith M_s≥6.0 since this century and the ...According to the earthquake focal mechanism solutions of 55 moderately strong earthquakes onthe northeastern side of Pamirs,the spatial and temporal distribution of earthquakes ith M_s≥6.0 since this century and the characteristics of hypocenter depth distribution of earthquakeswith M_s≥3.0 since 1980 in this region,the article discusses the relation between regional tee-tonic stress fields and strong earthquake activity.The result shows that the hypocenter disloca-tion is mostly strike-dip,partly dip-slip,and the direction of the principal compressional stressis nearly NS.The distributive characteristics of strong shock activity is obvious,with the gen-eral trend that the west is strong and the east is weak,which can be divided into three imephases,and each with relative principal active region The depth near Pamirs aren reaches200km,shallower obviously when externding to NE,less than or equal to 40km near the Kalpinblock,and the article discusses the result.展开更多
ccording to the fracture mechanics rupture model of earthquakes put forward by us, several equations to compute tectonic ambient shear stress value τ0 have been derived [equations (1), (2), (3), (5)].τ0 values for i...ccording to the fracture mechanics rupture model of earthquakes put forward by us, several equations to compute tectonic ambient shear stress value τ0 have been derived [equations (1), (2), (3), (5)].τ0 values for intermediate and small earthquakes occurred in Chinese mainland and Southern California have been calculated by use of these equations. The results demonstrate that the level and distribution of τ0 are closely related to the location where large earthquakes will occur, i.e. the region with higher level of τ0 will be prone to occur large earthquakes and the region with lower level will usually occur small earthquakes. According to the spatial distribution of τ0 , the seismic hazard regions or the potential earthquake source regions can in some degree be determined. According to the variation of τ0 with time, the large earthquake occurrence time can be roughly estimated. According to the distribution of τ0 in Southern California and variation with time, three high stress level regions are determined, one (Goldfield area) of them is the present seismic hazard region.展开更多
This paper examines major active faults and the present-day tectonic stress field in the East Tibetan Plateau by integrating available data from published literature and proposes a block kinematics model of the region...This paper examines major active faults and the present-day tectonic stress field in the East Tibetan Plateau by integrating available data from published literature and proposes a block kinematics model of the region. It shows that the East Tibetan Plateau is dominated by strike-slip and reverse faulting stress regimes and that the maximum horizontal stress is roughly consistent with the contemporary velocity field, except for the west Qinling range where it parallels the striking of the major strike-slip faults. Active tectonics in the East Tibetan Plateau is characterized by three faulting systems. The left-slip Kunlun-Qinling faulting system combines the east Kunlun fault zone, sinistral oblique reverse faults along the Minshan range and two major NEE-striking faults cutting the west Qinling range, which accommodates eastward motion, at 10--14 mm/a, of the Chuan-Qing block. The left-slip Xianshuihe faulting system accommodated clockwise rotation of the Chuan-Dian block. The Longmenshan thrust faulting system forms the eastern margin of the East Tibetan Plateau and has been propagated to the SW of the Sichuan basin. Crustal shortening across the Longmenshan range seems low (2-4 mm/a) and absorbed only a small part of the eastward motion of the Chuan-Qing block. Most of this eastward motion has been transmitted to South China, which is moving SEE-ward at 7-9 mm/a. It is suggested from geophysical data interpretation that the crust and lithosphere of the East Tibetan Plateau is considerably thickened and theologically layered. The upper crust seems to be decoupled from the lower crust through a decollement zone at a depth of 15-20 kin, which involved the Longmenshan fault belt and propagated eastward to the SW of the Sichuan basin. The Wenchuan earthquake was just formed at the bifurcated point of this decollement system. A rheological boundary should exist beneath the Longmenshan fault belt where the lower crust of the East Tibetan Plateau and the lithospheric mantle of the Yangze block are juxtaposed.展开更多
The focal mechanisms of 62 moderate-small earthquakes since 1980 in the"Huoshan seismic window"region are calculated with the method developed recently by Snoke,combining the use of the first motion of P,SV ...The focal mechanisms of 62 moderate-small earthquakes since 1980 in the"Huoshan seismic window"region are calculated with the method developed recently by Snoke,combining the use of the first motion of P,SV and SH waves with their amplitude ratios.Based on these abundant focal mechanisms,the mean tectonic stress field in the"Huoshan seismic window"region is inverted with the average stress tensor method,and the result shows that the"Huoshan seismic window"region is horizontally compressed in the near EW direction and horizontally dilated in the near NS direction,which is in accord with statistical results of focal mechanism parameters.We estimate the difference(also referred to as consistency parameterθ)between the force axis direction of the focal mechanism solution and the mean stress tensor,then further analyze the variation characteristics ofθversus time,and the relationship with moderately strong earthquakes in the east China region.The result indicates thatθin the"Huoshan seismic window"region is in good correspondence with moderately strong earthquakes in the East China region.Whenθis lower than the mean value,corresponding moderately strong earthquakes may occur in the East China region.展开更多
By means of inversion of fault slip data, the parameters of 20 tectonic stress tensors in Southwest Yunnan region are determined. Compared with the average stress field of the region obtained from focal mechanism solu...By means of inversion of fault slip data, the parameters of 20 tectonic stress tensors in Southwest Yunnan region are determined. Compared with the average stress field of the region obtained from focal mechanism solutions, the following characteristics of modern tectonic stress field in this region are obtained. From the west of Zhenyuan-Yingpanshan fault to the south of Longling fault zone, the maximum compressional stress is in NNE direction and the stress regime is mainly of strike-slip type. In Longling fault zone and the area north to it, the direction of maximum compressional stress is near-NS or NNW, the stress regime is of strike-slip type.展开更多
The relationship between the earth stress field, earth surface displacement field and the gravity variation is deduced. Algorithms based on the boundary element method to compute the earth stress variation using the e...The relationship between the earth stress field, earth surface displacement field and the gravity variation is deduced. Algorithms based on the boundary element method to compute the earth stress variation using the earth surface displacement is discussed. The stress field variation in Jiashi region, Xinjiang, China is obtained from the GPS data observed in 1997 and 1998, respectively, and the relationship among the local stress field variation, seismic activities and fault tectonic activities is discussed.展开更多
It has been analyzed the influence of the tectonic ambient shear stress value on response spectrum based on the previous theory. Based on the prediction equation BJF94 presented by the famous American researchers, CLB...It has been analyzed the influence of the tectonic ambient shear stress value on response spectrum based on the previous theory. Based on the prediction equation BJF94 presented by the famous American researchers, CLB20, a new prediction formula is proposed by us, where it is introduced the influence of tectonic ambient shear stress value on response spectrum. BJF94 is the prediction equation, which mainly depends on strong ground motion data from western USA, while the prediction equation SEA99 is based on the strong ground motion data from exten-sional region all over the world. Comparing these two prediction equations in detail, it is found that after BJF94′s prediction value lg(Y) minus 0.16 logarithmic units, the value is very close to SEA99′s one. This case demonstrates that lg(Y) in extensional region is smaller; the differences of prediction equation are mainly owe to the differences of tectonic ambient shear stress value. If the factor of tectonic ambient shear stress value is included into the pre-diction equation, and the magnitude is used seismic moment magnitude to express, which is universal used around the world, and the distance is used the distance of fault project, which commonly used by many people, then re-gional differences of prediction equation will become much less, even vanish, and it can be constructed the uni-versal prediction equation proper to all over the world. The error in the earthquake-resistant design in China will be small if we directly use the results of response spectrum of USA (e.g. BJF94 or SEA99).展开更多
文摘This paper made a numerical simulation to the basic tectonic stress field of Chinese mainland and its neighboringregion using the visco-elasticity finite element model and the new published displacement rate result. Main contents include the simulation of maximum shear stress and its varying rate, the maximum shear strain and its varyingrate, the shear strain energy density and its varying rate. In view of the high inhomogeneous distribution characterof seismicity in space and time in Chinese mainland and its neighboring area, the normalized background energyvalue was given by means of normalized treatment to the earthquake energy release in the eastern and westernparts of Chinese mainland. And the comparison of the simulation result with the actual seismicity was made. Thefesults show that the simulation values can explain well the earthquake distribution character of Chinese mainlandand its neighboring area.
基金supported by research grant from Institute of Crustal Dynamics,China Earthquake Administration(No.ZDJ2009-06)special research grant from Institute of Crustal Dynamics,China Earthquake Administration(No.ZDJ2007-01)
文摘On the basis of a 3-dimension visco-elastic finite element model of lithosphere in North China, we numerically simulate the recent mutative figures of tectonic stress field. Annual change characteristics of stress field are: 1 ) Maximum principal tensile stress is about 3 -9 kPaa-1 and its azimuth lie in NNW-SSE. 2) Maximum principal compressive stress is about 1 - 6 kPaa-1 and its azimuth lie in NEE-SWW. 3 ) Maximum principal tensile stress is higher both in the west region and Liaoning Province. 4) Variation of tectonic stress field benefits fault movement in the west part and northeast part of North China. 5 )Annual accumulative rates of Coulomb fracture stress in Tanlu fault belt have segmentation patterns: Jiashan-Guangji segment is the high- est (6 kPaa - 1 ) , Anshan-Liaodongwan segment is the second (5 kPaa - l ) , and others are relatively lower ( 3 - 4 kPaa-1 ).
基金This research was sponsored by the National Key Basic Research Program under grant No. G1998040705 and National Key Scientific Program (96-913-07-04). China.
文摘According to the earthquake focal mechanism solutions of 55 moderately strong earthquakes onthe northeastern side of Pamirs,the spatial and temporal distribution of earthquakes ith M_s≥6.0 since this century and the characteristics of hypocenter depth distribution of earthquakeswith M_s≥3.0 since 1980 in this region,the article discusses the relation between regional tee-tonic stress fields and strong earthquake activity.The result shows that the hypocenter disloca-tion is mostly strike-dip,partly dip-slip,and the direction of the principal compressional stressis nearly NS.The distributive characteristics of strong shock activity is obvious,with the gen-eral trend that the west is strong and the east is weak,which can be divided into three imephases,and each with relative principal active region The depth near Pamirs aren reaches200km,shallower obviously when externding to NE,less than or equal to 40km near the Kalpinblock,and the article discusses the result.
文摘ccording to the fracture mechanics rupture model of earthquakes put forward by us, several equations to compute tectonic ambient shear stress value τ0 have been derived [equations (1), (2), (3), (5)].τ0 values for intermediate and small earthquakes occurred in Chinese mainland and Southern California have been calculated by use of these equations. The results demonstrate that the level and distribution of τ0 are closely related to the location where large earthquakes will occur, i.e. the region with higher level of τ0 will be prone to occur large earthquakes and the region with lower level will usually occur small earthquakes. According to the spatial distribution of τ0 , the seismic hazard regions or the potential earthquake source regions can in some degree be determined. According to the variation of τ0 with time, the large earthquake occurrence time can be roughly estimated. According to the distribution of τ0 in Southern California and variation with time, three high stress level regions are determined, one (Goldfield area) of them is the present seismic hazard region.
基金the auspice of National Key Basic Project(973)(granted number 2008CB425702)National Science and Technology Project(granted Number SinoProbe-08)China Geological Survey project(granted number1212010670104)
文摘This paper examines major active faults and the present-day tectonic stress field in the East Tibetan Plateau by integrating available data from published literature and proposes a block kinematics model of the region. It shows that the East Tibetan Plateau is dominated by strike-slip and reverse faulting stress regimes and that the maximum horizontal stress is roughly consistent with the contemporary velocity field, except for the west Qinling range where it parallels the striking of the major strike-slip faults. Active tectonics in the East Tibetan Plateau is characterized by three faulting systems. The left-slip Kunlun-Qinling faulting system combines the east Kunlun fault zone, sinistral oblique reverse faults along the Minshan range and two major NEE-striking faults cutting the west Qinling range, which accommodates eastward motion, at 10--14 mm/a, of the Chuan-Qing block. The left-slip Xianshuihe faulting system accommodated clockwise rotation of the Chuan-Dian block. The Longmenshan thrust faulting system forms the eastern margin of the East Tibetan Plateau and has been propagated to the SW of the Sichuan basin. Crustal shortening across the Longmenshan range seems low (2-4 mm/a) and absorbed only a small part of the eastward motion of the Chuan-Qing block. Most of this eastward motion has been transmitted to South China, which is moving SEE-ward at 7-9 mm/a. It is suggested from geophysical data interpretation that the crust and lithosphere of the East Tibetan Plateau is considerably thickened and theologically layered. The upper crust seems to be decoupled from the lower crust through a decollement zone at a depth of 15-20 kin, which involved the Longmenshan fault belt and propagated eastward to the SW of the Sichuan basin. The Wenchuan earthquake was just formed at the bifurcated point of this decollement system. A rheological boundary should exist beneath the Longmenshan fault belt where the lower crust of the East Tibetan Plateau and the lithospheric mantle of the Yangze block are juxtaposed.
基金funded by the Youth Program of Earthquake Scientific Research Fund of Anhui Province(20120704)Contract Subject of Earthquake Administration of Anhui Province(201210)
文摘The focal mechanisms of 62 moderate-small earthquakes since 1980 in the"Huoshan seismic window"region are calculated with the method developed recently by Snoke,combining the use of the first motion of P,SV and SH waves with their amplitude ratios.Based on these abundant focal mechanisms,the mean tectonic stress field in the"Huoshan seismic window"region is inverted with the average stress tensor method,and the result shows that the"Huoshan seismic window"region is horizontally compressed in the near EW direction and horizontally dilated in the near NS direction,which is in accord with statistical results of focal mechanism parameters.We estimate the difference(also referred to as consistency parameterθ)between the force axis direction of the focal mechanism solution and the mean stress tensor,then further analyze the variation characteristics ofθversus time,and the relationship with moderately strong earthquakes in the east China region.The result indicates thatθin the"Huoshan seismic window"region is in good correspondence with moderately strong earthquakes in the East China region.Whenθis lower than the mean value,corresponding moderately strong earthquakes may occur in the East China region.
基金Chinese Joint Seismological Science Foundation (9507424).Contribution No. 2001A001, Institute of Crustal Dynamics, China Seism
文摘By means of inversion of fault slip data, the parameters of 20 tectonic stress tensors in Southwest Yunnan region are determined. Compared with the average stress field of the region obtained from focal mechanism solutions, the following characteristics of modern tectonic stress field in this region are obtained. From the west of Zhenyuan-Yingpanshan fault to the south of Longling fault zone, the maximum compressional stress is in NNE direction and the stress regime is mainly of strike-slip type. In Longling fault zone and the area north to it, the direction of maximum compressional stress is near-NS or NNW, the stress regime is of strike-slip type.
基金State Natural Science Foundation of China !(49774214)the State Key Project !(96-913-07).
文摘The relationship between the earth stress field, earth surface displacement field and the gravity variation is deduced. Algorithms based on the boundary element method to compute the earth stress variation using the earth surface displacement is discussed. The stress field variation in Jiashi region, Xinjiang, China is obtained from the GPS data observed in 1997 and 1998, respectively, and the relationship among the local stress field variation, seismic activities and fault tectonic activities is discussed.
基金National Natural Science Foundation of China (49874010)
文摘It has been analyzed the influence of the tectonic ambient shear stress value on response spectrum based on the previous theory. Based on the prediction equation BJF94 presented by the famous American researchers, CLB20, a new prediction formula is proposed by us, where it is introduced the influence of tectonic ambient shear stress value on response spectrum. BJF94 is the prediction equation, which mainly depends on strong ground motion data from western USA, while the prediction equation SEA99 is based on the strong ground motion data from exten-sional region all over the world. Comparing these two prediction equations in detail, it is found that after BJF94′s prediction value lg(Y) minus 0.16 logarithmic units, the value is very close to SEA99′s one. This case demonstrates that lg(Y) in extensional region is smaller; the differences of prediction equation are mainly owe to the differences of tectonic ambient shear stress value. If the factor of tectonic ambient shear stress value is included into the pre-diction equation, and the magnitude is used seismic moment magnitude to express, which is universal used around the world, and the distance is used the distance of fault project, which commonly used by many people, then re-gional differences of prediction equation will become much less, even vanish, and it can be constructed the uni-versal prediction equation proper to all over the world. The error in the earthquake-resistant design in China will be small if we directly use the results of response spectrum of USA (e.g. BJF94 or SEA99).