The Wenchuan earthquake has altered the crustal motion characteristics in the eastern margin of the Tibetan Plateau and adjacent regions.Using discontinuous GPS survey data for 2008–2012, the velocity field for the E...The Wenchuan earthquake has altered the crustal motion characteristics in the eastern margin of the Tibetan Plateau and adjacent regions.Using discontinuous GPS survey data for 2008–2012, the velocity field for the Eurasia reference framework has been obtained, and the general trend of contemporary crustal motion after the occurrence of the Wenchuan earthquake has been studied.In addition, using the velocity field, the block movement velocity has been estimated by least-squares fitting.Furthermore, the properties and displacement rates of main faults have been obtained from the differences in velocity vectors of the blocks on both sides of the faults.The results reveal that there are no obvious changes in the general characteristics of crustal motion in this area after the Wenchuan earthquake.The earthquake mainly changed the rate of the movement of the Chuan-Qing block and caused variation in the movement direction of the South China block.The effect of the earthquake on faults is mainly reflected in variations in fault displacement velocity; there is no fundamental change in the properties of fault activity.The displacement rates of the Xianshuihe fault decreased by 3–4 mm/a, the Longmenshan fault increased by 9–10 mm/a, and the northern segment of the Anninghe fault increased by approximately 9 mm/a.Furthermore, the displacement rates of the Minjiang, Xueshan, Huya, Longquanshan, and Xinjin faults increased by 2–3 mm/a.This implies that the effects of the Wenchuan earthquake on crustal movement can mainly be observed in the Chuan-Qing, South China, and N-Chuan-Dian blocks and their internal faults, as well as the Xianshuihe and Longmenshan faults and the northern section of the Anninghe fault.The reason for this is that the Wenchuan earthquake disturbed the kinematic and dynamic balance in the region.展开更多
: To measure and monitor the crustal motion in China, a GPS network has been established with an average side length of 1 000 km and with more than 20 points on the margins of each major tectonic block and fault zone ...: To measure and monitor the crustal motion in China, a GPS network has been established with an average side length of 1 000 km and with more than 20 points on the margins of each major tectonic block and fault zone in China. Three campaigns were carried out in 1992,1994 and 1996, respectively by this network. Here we present, for the first time, the horizontal displacement rates of 22 GPS monitoring stations distributed over the whole China and global IGS stations surrounding China, based on these GPS repeated measurements. From these results by GPS, we have obtained the sketch of crustal motion in China.展开更多
Through GPS carrier phases observation in southwestern China during 1991-1997,the velocity field within eastern Qinghai-Xizang (Tibet) and its neighbour regions has been es-’tablished. The velocity of those sites in ...Through GPS carrier phases observation in southwestern China during 1991-1997,the velocity field within eastern Qinghai-Xizang (Tibet) and its neighbour regions has been es-’tablished. The velocity of those sites in and west of Chuan-Dian block is mostly 5-10 mm·a-1relative to the fiduciary station CHDU (Chengdu), and the motion in Chuan-Qing and展开更多
On the basis of distribution of active fault and regional rheological structure, a three-dimensional finite element model of Sichuan-Yunnan region, China, is constructed to simulate contemporary crustal motion and str...On the basis of distribution of active fault and regional rheological structure, a three-dimensional finite element model of Sichuan-Yunnan region, China, is constructed to simulate contemporary crustal motion and stress distribution and discuss the dynamic mechanism of crustal motion and deformation in the Sichuan-Yunnan region. Linear Maxwell visco-elastic model is applied, which includes the active fault zones, the elastic upper crust and viscous lower crust and upper mantle. Four different models with different boundary conditions and deep structure are calculated. Some conclusions are drawn through comparison. Firstly, the crustal rotation about the eastern syntaxis of the Himalaya in the Sicuan-Yunnan region may be controlled by the special dynamic boundary condition. The drag force of the lower-crust on the upper crust is not negligible. At the same time, the main active fault zones play an important role in the contemporary crustal motion and deformation in Sichuan-Yunnan region.展开更多
An Ms6.4 earthquake occurred in the Menyuan county of Qinghai Province on Jan 21, 2016. In order to recognize the development of horizontal deformation and distinguish precursory deformation anomalies, we obtained coo...An Ms6.4 earthquake occurred in the Menyuan county of Qinghai Province on Jan 21, 2016. In order to recognize the development of horizontal deformation and distinguish precursory deformation anomalies, we obtained coordinates time series, velocity and strain model around the seismic zones from processing of continuous observations from 2010 and 6 times of surveying Global Positioning System （GPS） data since 2009. The results show that, before the earthquake, the eastern segmentation of the Qilian tectonic zone where the Lenglongling Fault located is in strong crustal shortening and compressional strain state with dilatational rates of -15 to -25 ppb. The Lenglongling Fault has a strike-slip rate of 3.1 mm/a and a far-field differential orthogonal rate of 7 mm/a, while differential rate is only 1.2 mm/a near the fault, which reflects its locking feature with strain energy accumulation and high seismic risks. Dynamic evolution of deformation model shows that preevent dilatational rates around the seismic zones increases from 15 ppb/a to -20 ppb/a with its center moving to the source areas. Time series of N components of G337 station, which is 13.7 km away from the Lenglongling Fault, exhibit a 5 mm/a acceleration anomaly. Time series of base-station QHME （in Menyuan） displays a reverse acceleration from the end of Sep. to Dec., 2016 when it comes to a largest deviation, and the accumulative displacement is more than 4 mm and the value reverse till the earthquake. In our results, coseismic displacement of N, E, U components in QHME site are 3.0 mm, 3.0 mm, -5.4 mm, respectively. If we profile these values onto the Lenglongling Fault, we can achieve a 1.1 mm of strike slip and 4.1 mm updip slip relative to the hanging wall.展开更多
A method for computing crustal horizontal velocities and strain-rates using repeated GPS survey and other crustal deformation measurement was presented in detail. Based on the data taken from the Crustal Deformation M...A method for computing crustal horizontal velocities and strain-rates using repeated GPS survey and other crustal deformation measurement was presented in detail. Based on the data taken from the Crustal Deformation Monitoring-Networks with GPS in the whole country and North China, we derived the average horizontal velocities of the points of the networks and simulated the horizontal velocity and strain-rate fields in the corresponding areas. From these results, we can conclude: (1) GPS can effectively detect current crustal motion and deformation, and (2) the method presented in the paper is valid, and through its use, calculated results can provide more information about current crustal motion and deformation than direct observation data.展开更多
Based on the dynamic monitoring data of crustal deformation, the parameter evolution for the dynamics pattern and fractal dimension of crustal deformation field and the integral activity level of many faults etc. befo...Based on the dynamic monitoring data of crustal deformation, the parameter evolution for the dynamics pattern and fractal dimension of crustal deformation field and the integral activity level of many faults etc. before and after the Tangshan (1976) and Lijiang (1996) strong earthquakes and others are studied by using the method of pattern dynamics. It is exposed that two time space characters, the ordered dimension drop of the deformation field and the accelerated motion of multi fault before an earthquake, are probably caused by the deformation localization and fault softening after the seismogenic process enters the nonlinear stage. They could be an important seismic precursor if they occurred repeatedly before strong earthquakes.展开更多
基金supported by a geological survey project of the China Geological Survey (No.1212011140013, No.12120113009800)
文摘The Wenchuan earthquake has altered the crustal motion characteristics in the eastern margin of the Tibetan Plateau and adjacent regions.Using discontinuous GPS survey data for 2008–2012, the velocity field for the Eurasia reference framework has been obtained, and the general trend of contemporary crustal motion after the occurrence of the Wenchuan earthquake has been studied.In addition, using the velocity field, the block movement velocity has been estimated by least-squares fitting.Furthermore, the properties and displacement rates of main faults have been obtained from the differences in velocity vectors of the blocks on both sides of the faults.The results reveal that there are no obvious changes in the general characteristics of crustal motion in this area after the Wenchuan earthquake.The earthquake mainly changed the rate of the movement of the Chuan-Qing block and caused variation in the movement direction of the South China block.The effect of the earthquake on faults is mainly reflected in variations in fault displacement velocity; there is no fundamental change in the properties of fault activity.The displacement rates of the Xianshuihe fault decreased by 3–4 mm/a, the Longmenshan fault increased by 9–10 mm/a, and the northern segment of the Anninghe fault increased by approximately 9 mm/a.Furthermore, the displacement rates of the Minjiang, Xueshan, Huya, Longquanshan, and Xinjin faults increased by 2–3 mm/a.This implies that the effects of the Wenchuan earthquake on crustal movement can mainly be observed in the Chuan-Qing, South China, and N-Chuan-Dian blocks and their internal faults, as well as the Xianshuihe and Longmenshan faults and the northern section of the Anninghe fault.The reason for this is that the Wenchuan earthquake disturbed the kinematic and dynamic balance in the region.
文摘: To measure and monitor the crustal motion in China, a GPS network has been established with an average side length of 1 000 km and with more than 20 points on the margins of each major tectonic block and fault zone in China. Three campaigns were carried out in 1992,1994 and 1996, respectively by this network. Here we present, for the first time, the horizontal displacement rates of 22 GPS monitoring stations distributed over the whole China and global IGS stations surrounding China, based on these GPS repeated measurements. From these results by GPS, we have obtained the sketch of crustal motion in China.
文摘Through GPS carrier phases observation in southwestern China during 1991-1997,the velocity field within eastern Qinghai-Xizang (Tibet) and its neighbour regions has been es-’tablished. The velocity of those sites in and west of Chuan-Dian block is mostly 5-10 mm·a-1relative to the fiduciary station CHDU (Chengdu), and the motion in Chuan-Qing and
基金Ministry of Science and Technology (2004CB418406, 2005DKA64000)the Basic Science Research Plan of the Institute of Earthquake Science, China Earthquake Administration (02076902-03).
文摘On the basis of distribution of active fault and regional rheological structure, a three-dimensional finite element model of Sichuan-Yunnan region, China, is constructed to simulate contemporary crustal motion and stress distribution and discuss the dynamic mechanism of crustal motion and deformation in the Sichuan-Yunnan region. Linear Maxwell visco-elastic model is applied, which includes the active fault zones, the elastic upper crust and viscous lower crust and upper mantle. Four different models with different boundary conditions and deep structure are calculated. Some conclusions are drawn through comparison. Firstly, the crustal rotation about the eastern syntaxis of the Himalaya in the Sicuan-Yunnan region may be controlled by the special dynamic boundary condition. The drag force of the lower-crust on the upper crust is not negligible. At the same time, the main active fault zones play an important role in the contemporary crustal motion and deformation in Sichuan-Yunnan region.
基金support by National Natural Science Foundation of China(51479163,41174083)
文摘An Ms6.4 earthquake occurred in the Menyuan county of Qinghai Province on Jan 21, 2016. In order to recognize the development of horizontal deformation and distinguish precursory deformation anomalies, we obtained coordinates time series, velocity and strain model around the seismic zones from processing of continuous observations from 2010 and 6 times of surveying Global Positioning System （GPS） data since 2009. The results show that, before the earthquake, the eastern segmentation of the Qilian tectonic zone where the Lenglongling Fault located is in strong crustal shortening and compressional strain state with dilatational rates of -15 to -25 ppb. The Lenglongling Fault has a strike-slip rate of 3.1 mm/a and a far-field differential orthogonal rate of 7 mm/a, while differential rate is only 1.2 mm/a near the fault, which reflects its locking feature with strain energy accumulation and high seismic risks. Dynamic evolution of deformation model shows that preevent dilatational rates around the seismic zones increases from 15 ppb/a to -20 ppb/a with its center moving to the source areas. Time series of N components of G337 station, which is 13.7 km away from the Lenglongling Fault, exhibit a 5 mm/a acceleration anomaly. Time series of base-station QHME （in Menyuan） displays a reverse acceleration from the end of Sep. to Dec., 2016 when it comes to a largest deviation, and the accumulative displacement is more than 4 mm and the value reverse till the earthquake. In our results, coseismic displacement of N, E, U components in QHME site are 3.0 mm, 3.0 mm, -5.4 mm, respectively. If we profile these values onto the Lenglongling Fault, we can achieve a 1.1 mm of strike slip and 4.1 mm updip slip relative to the hanging wall.
文摘A method for computing crustal horizontal velocities and strain-rates using repeated GPS survey and other crustal deformation measurement was presented in detail. Based on the data taken from the Crustal Deformation Monitoring-Networks with GPS in the whole country and North China, we derived the average horizontal velocities of the points of the networks and simulated the horizontal velocity and strain-rate fields in the corresponding areas. From these results, we can conclude: (1) GPS can effectively detect current crustal motion and deformation, and (2) the method presented in the paper is valid, and through its use, calculated results can provide more information about current crustal motion and deformation than direct observation data.
文摘Based on the dynamic monitoring data of crustal deformation, the parameter evolution for the dynamics pattern and fractal dimension of crustal deformation field and the integral activity level of many faults etc. before and after the Tangshan (1976) and Lijiang (1996) strong earthquakes and others are studied by using the method of pattern dynamics. It is exposed that two time space characters, the ordered dimension drop of the deformation field and the accelerated motion of multi fault before an earthquake, are probably caused by the deformation localization and fault softening after the seismogenic process enters the nonlinear stage. They could be an important seismic precursor if they occurred repeatedly before strong earthquakes.
