In this paper, progress in strain study of blocks and faults by GPS data are discussed, and the concept that active structures between blocks are the main body of crustal strain is clarified. By energy transfer princi...In this paper, progress in strain study of blocks and faults by GPS data are discussed, and the concept that active structures between blocks are the main body of crustal strain is clarified. By energy transfer principle of elastic mechanics, the relation between strain around faults and tectonic force on fault surfaces is set up and main body element model of crustal strain is constructed. Finally, the relation between mechanical evolution of model and seismogenic process of Kunlun earthquake (Ms=8.1) is discussed by continuous GPS data of datum stations. The result suggests that the relatively relaxed change under background of strong compressing and shearing may help to trigger moderate-strong earthquakes.展开更多
The relationship between the strain cumulative rate (i.e., the crustal strain rate, or CSR in short) and seismic activity is analyzed to develop a new method to determine risky regions for strong shocks within recent ...The relationship between the strain cumulative rate (i.e., the crustal strain rate, or CSR in short) and seismic activity is analyzed to develop a new method to determine risky regions for strong shocks within recent years by the recorded crustal strain field. Seismic activity, especially the recurrence period, is different in different areas. Ding Guoyu (1984) pointed out that, for different seismic regions, the difference in the recurrence period of strong earthquakes is mainly controlled by their difference in the rate of the tectonic movement, which is controlled by the seismogenic environment and the tectonic conditions. The method of determining the risky regions for strong shocks from the gradient of vertical strain rates observed in a geodetic survey is preliminarily tested with the earthquakes in recent years; the results show that this method is effective and useful for earthquake prediction. The relationship between CSR and seismicity in a specific region is studied with strain theories,展开更多
This work analyzes the quality of crustal tilt and strain observations during 2014, which were acquired from 269 sets of ground tiltmeters and 212 sets of strainmeters. In terms of data quality, the water tube tiltmet...This work analyzes the quality of crustal tilt and strain observations during 2014, which were acquired from 269 sets of ground tiltmeters and 212 sets of strainmeters. In terms of data quality, the water tube tiltmeters presented the highest rate of excellent quality,approximately 91%, and the pendulum tiltmeters and ground strainmeters yielded rates of81% and 78%, respectively. This means that a total of 380 sets of instruments produced high-quality observational data suitable for scientific investigations and analyses.展开更多
Three-dimensional(3 D) co-seismic surface deformations are of great importance to interpret the characteristics of coseismic deformations and to understand the geometries and dynamics of seismogenic faults. In this pa...Three-dimensional(3 D) co-seismic surface deformations are of great importance to interpret the characteristics of coseismic deformations and to understand the geometries and dynamics of seismogenic faults. In this paper, we propose a method for mapping 3 D co-seismic deformations based on InSAR observations and crustal strain characteristics. In addition, the search strategy of correlation points is optimized by adaptive correlation distance, which greatly improves the applicability of the proposed method in restoring deformations in decorrelation areas. Results of the simulation experiment reveal that the proposed method is superior to conventional methods in both the accuracy and completeness. The proposed method is then applied to map the 3 D co-seismic surface deformations associated with the 2015 MW7.2 Murghab earthquake using ascending and descending ALOS-2 PALSAR-2 images. The results show that the seismogenic fault is the Sarez-Karakul fault(SKF), which is dominated by NE-SW strike slips with an almost vertical dip angle. The north section and the south segment near the epicentre have obvious subsidence along with a southwestward motion in the northwest wall, and the southeast wall has northeast movement and surface uplift trend along the fault zone. The strain field of the earthquake is also obtained by the proposed method. It is found that the crustal block of the seismic area is obviously affected by dilatation and shear forces, which is in good agreement with the movement character of the sinistral slip.展开更多
In this paper, we analyze the crustal movements, strain field changes and large scale dynamic characteristics of horizontal deformation before the Wenchuan earthquake (M_S=8.0) using GPS data obtained from the Crustal...In this paper, we analyze the crustal movements, strain field changes and large scale dynamic characteristics of horizontal deformation before the Wenchuan earthquake (M_S=8.0) using GPS data obtained from the Crustal Movement Observation Network of China. The following issues are discussed. First, the strain fields of the Longmenshan fault zone located at the epicenter show slow accumulation, because of the tectonic dynamics process subjected to the eastward movement of the Bayan Har block. Second, the different movements between the Longmenshan fault and South China block are smaller than the errors of GPS observation. Third, the high value of compressive strain (2004~2007) is located at the epicenter, which shows that the local squeezing action is stronger than before. Fourth, the data from GPS reference stations in the Chinese Mainland show that crustal shortening is faster than before in the north-eastern direction, which is part of the background of the local tectonic dynamics increase in the Longmenshan fault zone.展开更多
The great Wenchuan earthquake of M8.0 on May 12, 2008, occurred in an area with dense GPS observation stations in the regional network of the Crustal Movement Observation Network of China (CMONOC). Non-continuous ob...The great Wenchuan earthquake of M8.0 on May 12, 2008, occurred in an area with dense GPS observation stations in the regional network of the Crustal Movement Observation Network of China (CMONOC). Non-continuous observations were carried out at the 1 000 GPS stations of the regional network in 1999, 2001, 2004 and 2007. The horizontal displacements at GPS stations in the regional network before the Wenchuan earthquake show that the main driving tectonic force of the earthquake was the northward pushing of the Indian plate, added at the same time by the pushing of plates on the east and south. In comparison to the displacements in other regions, the horizontal displacements near and around the seismic area is characterized by diverging eastward displacements, that is, the stations to the north of the epicenter moved in the ENE direction while those to the south of epicenter moved in ESE direction with smaller displacements at stations near the epicenter. The accuracy of the estimated strain results is briefly discussed. In order to obtain the anomalous information before the earthquake, the methods of both best fits by trend surface and statistics have been used in the study for finding the future epicentral area from the strain accumulations in the regional network observed from 1999 to 2007 before the Wenchuan earthquake. Besides the epicentral area of the western Kunlun mountain pass earthquake of M8.1 in 2001, the results of best fits by trend surfaces of the strain accumulations from 1999 to 2007 in the regional network show that the Wenchuan earthquake occurred at the eastern fringe of a large area with relatively large accumulations of the first shear strains and also at the northeastern fringe of a smaller area with significant accumulated areal compressions. The statistics of the accumulations of the strain components demonstrates that they also showed anomalous distribution pattems in this area and its neighborhood with increasing accumulations of both shear strains and areal compressions.展开更多
The foremost Global Positioning System(GPS) derived measurements in the Kumaun Himalaya indicate that most of the crustal motion of the Indian plate is accommodating towards the base as well as on the hanging wall of ...The foremost Global Positioning System(GPS) derived measurements in the Kumaun Himalaya indicate that most of the crustal motion of the Indian plate is accommodating towards the base as well as on the hanging wall of Main Central Thrust(MCT).Deformation pattern within the Kumaun Himalaya varies from south to north and indicates maximum deformation rate near MCT.Our study,based on the campaign mode GPS survey during 2003- 2006,reveals that the area between north of North Almora Thrust(NAT) and at the base of Great Himalaya registers maximum strain rate,which is lowered towards the Trans Himadri Fault(THF).The GAMIT-GLOBK processed campaign data of the area show that currently,the Himalayan Frontal Fault(HFF) and Main Boundary Thrust(MBT) are locked with the Indian plate,and a 6.7 ± 2.5 mm/yr of horizontal shortening is taking place between the Lesser Himalaya and Peninsular India.展开更多
In this paper, the horizontal crustal movement obtained from GPS observations in 1998 and 2000 at basic and fiducial stations in the Crustal Movement Observation Network of China (CMONOC) is introduced. A brief introd...In this paper, the horizontal crustal movement obtained from GPS observations in 1998 and 2000 at basic and fiducial stations in the Crustal Movement Observation Network of China (CMONOC) is introduced. A brief introduction of the field observations, the data processing with GAMIT/GLOBK software and the accuracy of the GPS observations is given. In average the accuracy of the results for each year is about 2 mm in the horizontal components and 5 mm in the vertical component, and the average accuracy of horizontal displacements at a station is about 3 mm. The results of crustal movement during the period from early September 1998 to mid June, 2000, including the displacements at each station with datum definition of a group of stable stations of insignificant relative movements among themselves in the eastern part of China, strains in different parts of the network and rotations in some parts, are obtained. Based on the crustal movement maps which are more complete and detailed than previous ones, the general characteristics of the recent crustal movement in Chinese mainland are discussed. During the above mentioned period of observations, the crustal deformation in the eastern part of China was relatively small and quite stable. With reference to a group of stable stations with small relative movement in the eastern part of China, the northeastern China block moved northward for about 10 mm, the South China block moved south-eastern for about 9 mm. In reference to the eastern part the northwestern part of China moved northward for about 26 mm, the Tibetan area in southwestern part of China moved mainly northward for about 32 mm. The area in Yunnan and east Tibet showed significant clockwise tectonic rotation of 0.0045 double prime or average rotational displacement of 12 mm with the rotation center at 26.5°N and 95.5°E. The North-South Seismic Belt in the middle part of China is of active and complicated deformation. The observation results show that the northward pushing by the Indian plate has still played the dominant role in the crustal movement in Chinese mainland.展开更多
Hainan Island,located at the southeast edge of the Eurasian Plate,is affected by the motion of multiple plates,with its northeast edge mainly dilatating and its western margin presently compressing. By analyzing the G...Hainan Island,located at the southeast edge of the Eurasian Plate,is affected by the motion of multiple plates,with its northeast edge mainly dilatating and its western margin presently compressing. By analyzing the GPS rates during 1999- 2007 in Hainan and its adjacent region,we determined horizontal movement rates of 3. 0-21. 1 mm /a at the west of 104°E,evidently affected by the Indian Plate extrusion.Their directions are SE-SN-SW from east to west and are separated by the main fault. The principal strains have the same characteristics. The stations east of 104°E move mainly in the SEE direction. The eastward rates are 2. 1-8. 5 mm /a and northward rates are 0. 4- 2. 7 mm /a. The GPS rates during 2009- 2013 show that stations at the edge of the island move SEE relative to the Eurasian Plate,with rates relative to the mean benchmark,indicating that there are small relative movements between stations,whereas QION station,located in the middle,moves in the NW direction at a greater rate. Vertical differential movement is apparent in the northeast zone of the island. Upwelling of mantle plume material possibly influences the local stress.Three-dimensional GPS rates indicate that,at present,inherited crustal movement is dominant in Hainan.展开更多
In this study, we analyze the regional GPS data of Crustal Movement Observation Network of China (CMONOC) observed from 2009-2013 using the BERNESE GPS software, and then the preliminary results of horizontal veloci...In this study, we analyze the regional GPS data of Crustal Movement Observation Network of China (CMONOC) observed from 2009-2013 using the BERNESE GPS software, and then the preliminary results of horizontal velocity field and strain rate field are presented, which could reflect the overall deformation features in the Chinese mainland from 2009-2013. Besides, the velocity error and the probable factors that could influence the estimate of long-term deformation are also discussed.展开更多
The purpose of this paper is to compare the strain energy released due to elastic rebound of the crust from the tragic 2011 9.0 MwTōhoku earthquake in Japan with the observed radiated seismic energy. The strain energ...The purpose of this paper is to compare the strain energy released due to elastic rebound of the crust from the tragic 2011 9.0 MwTōhoku earthquake in Japan with the observed radiated seismic energy. The strain energy was calculated by analyzing coseismic displacements of 1024 GPS stations of the Japanese GEONET network. The value of energy released from the analysis is 1.75 × 1017J, which is of the same order of magnitude as the USGS-observed radiated seismic energy of 1.9 × 1017Nm (J). The strain energy method is independent of seismic methods for determining the energy released during a large earthquake. The analysis shows that although the energy release is concentrated in the epicentral region, about 12% of the total energy was released throughout the Japanese islands at distances greater than 500 km west of the epicenter. Our results also show that outside the epicentral region, the strainenergy was concentrated along known tectonic zones throughout Japan.展开更多
In this paper, GPS observations during 1998 to 1999 at fiducial stations in the Crustal Movement Observation Network of China (CMONOC) and GPS observation data processing with Bernese Software are briefly introduced. ...In this paper, GPS observations during 1998 to 1999 at fiducial stations in the Crustal Movement Observation Network of China (CMONOC) and GPS observation data processing with Bernese Software are briefly introduced. The processed results of crustal movement in the network during the period from early September 1998 to early July 1999, including the displacements at each fiducial station and strains in different part of the network, are discussed in detail. During the above mentioned period of observations, the eastern part of China was relatively stable. In contrast, the southwest part of China moved northwards about 17 mm with a dominant compression in NNE; the northwestern part of China moved northwestwards about 11 mm; and the Yunnan area moved southwards about 14 mm. The North-South seismic belt in the middle part of China is a belt of strong shear deformation. The maximum principal strain in the network is 2.9×10-8. The observation result shows that the northward push by the Indian Plate has still played the dominant role in the crystal movement in China.展开更多
We analyzed 360 permanent and campaign GPS data from 1999 to 2017 in the southern Sichuan-Yunan block, and obtained crustal horizontal deformation in this region.Then, we derived the strain rate using a multi-scale sp...We analyzed 360 permanent and campaign GPS data from 1999 to 2017 in the southern Sichuan-Yunan block, and obtained crustal horizontal deformation in this region.Then, we derived the strain rate using a multi-scale spherical wavelet method.Results reveal a complex pattern of tectonic movement in the southern Sichuan-Yunnan block.Compared to the stable Eurasian plate, the maximum rate of the horizontal deformation in the southern Sichuan-Yunnan block is approximately 22 mm/a.The Xiaojiang fault shows a significantly lower deformation—a left-lateral strike-slip movement of 9.5 mm/a.The Honghe fault clearly shows a complex segmental deformation from the north to south.The northern Honghe fault shows 4.3 mm/a right strike-slip with 6.7 mm/a extension; the southern Honghe fault shows 1.9 mm/a right strike-slip with 1.9 mm/a extension; the junction zone in the Honghe and Lijiang–Xiaojinhe faults shows an obvious clockwise-rotation deformation.The strain calculation results reveal that the maximum shear-strain rate in this region reaches 70 nstrain/a, concentrated around the Xiaojiang fault and at the junction of the Honghe and Lijiang–Xiaojinhe faults.We note that most of the earthquakes with magnitudes of 4 and above that occurred in this region were within the high shear strain-rate zones and the strain rate gradient boundary zone, which indicates that the magnitude of strain accumulation is closely related to the seismic activities.Comparison of the fast shear-wave polarization direction of the upper-crust with the upper-mantle anisotropy and the direction of the surface principal compressive strain rate obtained from the inversion of the GPS data reveals that the direction of the surface principal compressive strain is basically consistent with the fast shear-wave polarization direction of the upper crust anisotropy, but different from the polarization direction of the upper mantle.Our results support the hypothesis that the principal elements of the deformation mechanism in the southern Sichuan-Yunnan block are decoupling between the upper and lower crust and ductile flow in the lower crust.展开更多
The sub-regions are divided for the seismicity of the Chinese mainland based on the hypothesis of the active crustal blocks and the division of the active boundaries. On this result, the seismicity of each active crus...The sub-regions are divided for the seismicity of the Chinese mainland based on the hypothesis of the active crustal blocks and the division of the active boundaries. On this result, the seismicity of each active crustal blocks are studied by calculating the accumulated and released strain of the earthquakes based on strain accumulating and releasing model, and the different seismicity stages of the sub-regions are discussed basically. Finally we have discussed the premise of the model application and the potential problems of the model results.展开更多
Borehole strain observation is playing an increasingly important role in the study on the crustal movements. It has been used by many countries such as China, USA, Japan, Peru, Australia, South Africa, Iceland and It...Borehole strain observation is playing an increasingly important role in the study on the crustal movements. It has been used by many countries such as China, USA, Japan, Peru, Australia, South Africa, Iceland and Italy, in re- search fields of plate tectonics, earthquake, volcanic eruption, dam safety, oil field subsidence, mining collapse and so on. Borehole strainmeter has been improved rapidly and tends to get more and more components included in one probe. Based on observations by this kind of instruments, studies on seismic strain step, slow earthquake, earthquake precursor and volcanic eruption forecasting have made remarkable achievements. In the coming years, borehole strain observation is going to become one major geodetic means, together with GPS and InSAR.展开更多
In the paper, the current strain field and stress field in Chinese continent have been discussedbased on the processed data from two GPS campaigns of national GPS network carried out inthe years of 1994 and 1996. With...In the paper, the current strain field and stress field in Chinese continent have been discussedbased on the processed data from two GPS campaigns of national GPS network carried out inthe years of 1994 and 1996. With a principal compressional strain direction of NNE, thewestern and castern parts of Qinghai-Xizang subplate are dominated by extensional straiu andthe central Part by compressional strain. Along the southwestern segment of southeastern partof Qinghai-Xizang subplate, i. e. Yunnan area, the princiPal compressional strain direction isNW and the compressional strain is equivalent to the extensional strain in magnitude. Theprincipal compressional strain of Xinjiang subplate is mainly NNE and NE with a difference inthe strain magnitude. The principal compressional strain in North China subplate is quite effective in NE and nearly EW directions with differences along some segments. However, thecompressional strain is corresponding to the extensional strain in magnitude in most areas.展开更多
GPS observation network is deployed in the central part of Ningxia, which is the juncture of the Alxa block, Ordos block and Qinghai-Xizang (Tibet) block. Using the data of five phases of repeated survey sine 1996, th...GPS observation network is deployed in the central part of Ningxia, which is the juncture of the Alxa block, Ordos block and Qinghai-Xizang (Tibet) block. Using the data of five phases of repeated survey sine 1996, the current state of crustal movement in the central part of Ningxia is analyzed. From the result, we can know the following. (1) In the period from Dec. 1996 to May 1999, the central part of Ningxia had the phenomenon of left-lateral movement about the west margin of Ordos (measuring station P2) and the Lingwu fault on the east of the Yinchuan basin displayed the mode of left-lateral reverse strike slip movement. In that region, the direction of the principal stress field was NNE-SSW (with an azimuth of 29.8?; the central part to the south of the measuring station P2 displaced eastward; the vertical deformation was obviously greater than the horizontal deformation in order of magnitude; the Yinchuan basin and Qinghai-Xizang (Tibet) block were in a state of rising; the measuring station P1 in the hinterland of Ordos showed a trend of subsiding year by year; and there may be a hidden fault to exist between the measuring points P3 and P4. (2) About one year before the occurrence of moderately strong earthquakes in the vicinity of the measuring region, deformation anomalies and abnormal changes of principal stress direction can be observed by the GPS measuring stations in that region; before moderately strong earthquakes near the measuring region and before strong earthquakes in adjacent regions, the simulated GPS deformation vector field ofthat region can betoken the approximate position of the coming earthquake. These results can be regarded as the eigenvalues of earthquake prediction for consideration.展开更多
Through numerical simulation for GPS data, aseismic negative dislocation model for crustal horizontal movement during 1999~2001 in the northeast margin of Qinghai-Xizang block is presented, combined with the spatial d...Through numerical simulation for GPS data, aseismic negative dislocation model for crustal horizontal movement during 1999~2001 in the northeast margin of Qinghai-Xizang block is presented, combined with the spatial distribution of apparent strain field in this area, the characteristics of motion and deformation of active blocks and their boundary faults, together with the place and intensity of strain accumulation are analyzed. It is shown that: a) 9 active blocks appeared totally clockwise motion from eastward by north to eastward by south. Obvious sinistral strike-slip and NE-NEE relative compressive motion between the blocks separated by Qilianshan-Haiyuan fault zone was discovered; b) 20 fault segments (most of them showed compression) locked the relative motion between blocks to varying degrees, among the total, the mid-east segment of Qilianshan fault (containing the place where it meets Riyueshan-Lajishan fault) and the place where it meets Haiyuan fault and Zhuanglanghe fault, more favored accumulation of strain. Moreover, the region where Riyueshan-Lajishan fault meets north boundary of Qaidam block may have strain accumulation to some degree. c) Obtained magnitude of block velocities and locking of their boundaries were less than relevant results for observation in the period of 1993~1999.展开更多
基金National Natural Science Foundation of China (40274023) and National Program for Key Science & Technology Projects (2004BA601B01-02-01).
文摘In this paper, progress in strain study of blocks and faults by GPS data are discussed, and the concept that active structures between blocks are the main body of crustal strain is clarified. By energy transfer principle of elastic mechanics, the relation between strain around faults and tectonic force on fault surfaces is set up and main body element model of crustal strain is constructed. Finally, the relation between mechanical evolution of model and seismogenic process of Kunlun earthquake (Ms=8.1) is discussed by continuous GPS data of datum stations. The result suggests that the relatively relaxed change under background of strong compressing and shearing may help to trigger moderate-strong earthquakes.
基金1998. This project was sponsored by the National Science Foundation (96-913-03-03-02), China.
文摘The relationship between the strain cumulative rate (i.e., the crustal strain rate, or CSR in short) and seismic activity is analyzed to develop a new method to determine risky regions for strong shocks within recent years by the recorded crustal strain field. Seismic activity, especially the recurrence period, is different in different areas. Ding Guoyu (1984) pointed out that, for different seismic regions, the difference in the recurrence period of strong earthquakes is mainly controlled by their difference in the rate of the tectonic movement, which is controlled by the seismogenic environment and the tectonic conditions. The method of determining the risky regions for strong shocks from the gradient of vertical strain rates observed in a geodetic survey is preliminarily tested with the earthquakes in recent years; the results show that this method is effective and useful for earthquake prediction. The relationship between CSR and seismicity in a specific region is studied with strain theories,
基金supported by Special Foundation of Earthquake Science(201408006)Director Foundation of Institute of Seismology,China Earthquake Administration(201516214)
文摘This work analyzes the quality of crustal tilt and strain observations during 2014, which were acquired from 269 sets of ground tiltmeters and 212 sets of strainmeters. In terms of data quality, the water tube tiltmeters presented the highest rate of excellent quality,approximately 91%, and the pendulum tiltmeters and ground strainmeters yielded rates of81% and 78%, respectively. This means that a total of 380 sets of instruments produced high-quality observational data suitable for scientific investigations and analyses.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41404011, 41674010 & 41704001)the Key Research and Development Plan of Hunan Province, China (Grant Nos. 2016SK2002 & 2017RS3001)+2 种基金the Innovation Platform Public Foundation of the Education Department of Hunan Province, China (Grant No. 16K053)the Land and Resource Department Scientific Research Program of Hunan Province, China (Grant No. 2017-13)the Special Funds for Basic Scientific Research Services of Central Higher Education Institutions of Central South University (Grant No. 2017ZZTS772)
文摘Three-dimensional(3 D) co-seismic surface deformations are of great importance to interpret the characteristics of coseismic deformations and to understand the geometries and dynamics of seismogenic faults. In this paper, we propose a method for mapping 3 D co-seismic deformations based on InSAR observations and crustal strain characteristics. In addition, the search strategy of correlation points is optimized by adaptive correlation distance, which greatly improves the applicability of the proposed method in restoring deformations in decorrelation areas. Results of the simulation experiment reveal that the proposed method is superior to conventional methods in both the accuracy and completeness. The proposed method is then applied to map the 3 D co-seismic surface deformations associated with the 2015 MW7.2 Murghab earthquake using ascending and descending ALOS-2 PALSAR-2 images. The results show that the seismogenic fault is the Sarez-Karakul fault(SKF), which is dominated by NE-SW strike slips with an almost vertical dip angle. The north section and the south segment near the epicentre have obvious subsidence along with a southwestward motion in the northwest wall, and the southeast wall has northeast movement and surface uplift trend along the fault zone. The strain field of the earthquake is also obtained by the proposed method. It is found that the crustal block of the seismic area is obviously affected by dilatation and shear forces, which is in good agreement with the movement character of the sinistral slip.
基金sponsored by the National Key Science and Technology R&D Program (2006BAC01B02-02-02)and National Natural Science Foundation of China(40674010)
文摘In this paper, we analyze the crustal movements, strain field changes and large scale dynamic characteristics of horizontal deformation before the Wenchuan earthquake (M_S=8.0) using GPS data obtained from the Crustal Movement Observation Network of China. The following issues are discussed. First, the strain fields of the Longmenshan fault zone located at the epicenter show slow accumulation, because of the tectonic dynamics process subjected to the eastward movement of the Bayan Har block. Second, the different movements between the Longmenshan fault and South China block are smaller than the errors of GPS observation. Third, the high value of compressive strain (2004~2007) is located at the epicenter, which shows that the local squeezing action is stronger than before. Fourth, the data from GPS reference stations in the Chinese Mainland show that crustal shortening is faster than before in the north-eastern direction, which is part of the background of the local tectonic dynamics increase in the Longmenshan fault zone.
基金supported by National Key Technology Research and Development Program (2006BAC01B02-02-05)Basic Research Plan of the Institute of Earthquake Science,China Earthquake Administration (0207690239)
文摘The great Wenchuan earthquake of M8.0 on May 12, 2008, occurred in an area with dense GPS observation stations in the regional network of the Crustal Movement Observation Network of China (CMONOC). Non-continuous observations were carried out at the 1 000 GPS stations of the regional network in 1999, 2001, 2004 and 2007. The horizontal displacements at GPS stations in the regional network before the Wenchuan earthquake show that the main driving tectonic force of the earthquake was the northward pushing of the Indian plate, added at the same time by the pushing of plates on the east and south. In comparison to the displacements in other regions, the horizontal displacements near and around the seismic area is characterized by diverging eastward displacements, that is, the stations to the north of the epicenter moved in the ENE direction while those to the south of epicenter moved in ESE direction with smaller displacements at stations near the epicenter. The accuracy of the estimated strain results is briefly discussed. In order to obtain the anomalous information before the earthquake, the methods of both best fits by trend surface and statistics have been used in the study for finding the future epicentral area from the strain accumulations in the regional network observed from 1999 to 2007 before the Wenchuan earthquake. Besides the epicentral area of the western Kunlun mountain pass earthquake of M8.1 in 2001, the results of best fits by trend surfaces of the strain accumulations from 1999 to 2007 in the regional network show that the Wenchuan earthquake occurred at the eastern fringe of a large area with relatively large accumulations of the first shear strains and also at the northeastern fringe of a smaller area with significant accumulated areal compressions. The statistics of the accumulations of the strain components demonstrates that they also showed anomalous distribution pattems in this area and its neighborhood with increasing accumulations of both shear strains and areal compressions.
文摘The foremost Global Positioning System(GPS) derived measurements in the Kumaun Himalaya indicate that most of the crustal motion of the Indian plate is accommodating towards the base as well as on the hanging wall of Main Central Thrust(MCT).Deformation pattern within the Kumaun Himalaya varies from south to north and indicates maximum deformation rate near MCT.Our study,based on the campaign mode GPS survey during 2003- 2006,reveals that the area between north of North Almora Thrust(NAT) and at the base of Great Himalaya registers maximum strain rate,which is lowered towards the Trans Himadri Fault(THF).The GAMIT-GLOBK processed campaign data of the area show that currently,the Himalayan Frontal Fault(HFF) and Main Boundary Thrust(MBT) are locked with the Indian plate,and a 6.7 ± 2.5 mm/yr of horizontal shortening is taking place between the Lesser Himalaya and Peninsular India.
基金National Development and Programing Project for Key Basic Researches (G1998040703).
文摘In this paper, the horizontal crustal movement obtained from GPS observations in 1998 and 2000 at basic and fiducial stations in the Crustal Movement Observation Network of China (CMONOC) is introduced. A brief introduction of the field observations, the data processing with GAMIT/GLOBK software and the accuracy of the GPS observations is given. In average the accuracy of the results for each year is about 2 mm in the horizontal components and 5 mm in the vertical component, and the average accuracy of horizontal displacements at a station is about 3 mm. The results of crustal movement during the period from early September 1998 to mid June, 2000, including the displacements at each station with datum definition of a group of stable stations of insignificant relative movements among themselves in the eastern part of China, strains in different parts of the network and rotations in some parts, are obtained. Based on the crustal movement maps which are more complete and detailed than previous ones, the general characteristics of the recent crustal movement in Chinese mainland are discussed. During the above mentioned period of observations, the crustal deformation in the eastern part of China was relatively small and quite stable. With reference to a group of stable stations with small relative movement in the eastern part of China, the northeastern China block moved northward for about 10 mm, the South China block moved south-eastern for about 9 mm. In reference to the eastern part the northwestern part of China moved northward for about 26 mm, the Tibetan area in southwestern part of China moved mainly northward for about 32 mm. The area in Yunnan and east Tibet showed significant clockwise tectonic rotation of 0.0045 double prime or average rotational displacement of 12 mm with the rotation center at 26.5°N and 95.5°E. The North-South Seismic Belt in the middle part of China is of active and complicated deformation. The observation results show that the northward pushing by the Indian plate has still played the dominant role in the crustal movement in Chinese mainland.
基金supported by the National Science Foundation of China(Grant No.41372345)
文摘Hainan Island,located at the southeast edge of the Eurasian Plate,is affected by the motion of multiple plates,with its northeast edge mainly dilatating and its western margin presently compressing. By analyzing the GPS rates during 1999- 2007 in Hainan and its adjacent region,we determined horizontal movement rates of 3. 0-21. 1 mm /a at the west of 104°E,evidently affected by the Indian Plate extrusion.Their directions are SE-SN-SW from east to west and are separated by the main fault. The principal strains have the same characteristics. The stations east of 104°E move mainly in the SEE direction. The eastward rates are 2. 1-8. 5 mm /a and northward rates are 0. 4- 2. 7 mm /a. The GPS rates during 2009- 2013 show that stations at the edge of the island move SEE relative to the Eurasian Plate,with rates relative to the mean benchmark,indicating that there are small relative movements between stations,whereas QION station,located in the middle,moves in the NW direction at a greater rate. Vertical differential movement is apparent in the northeast zone of the island. Upwelling of mantle plume material possibly influences the local stress.Three-dimensional GPS rates indicate that,at present,inherited crustal movement is dominant in Hainan.
基金supported by Foundation of Institute of Seismology,China Earthquake Administration(201326119)the National Natural Science Foundation of China(41074016,41274027,41304067)
文摘In this study, we analyze the regional GPS data of Crustal Movement Observation Network of China (CMONOC) observed from 2009-2013 using the BERNESE GPS software, and then the preliminary results of horizontal velocity field and strain rate field are presented, which could reflect the overall deformation features in the Chinese mainland from 2009-2013. Besides, the velocity error and the probable factors that could influence the estimate of long-term deformation are also discussed.
文摘The purpose of this paper is to compare the strain energy released due to elastic rebound of the crust from the tragic 2011 9.0 MwTōhoku earthquake in Japan with the observed radiated seismic energy. The strain energy was calculated by analyzing coseismic displacements of 1024 GPS stations of the Japanese GEONET network. The value of energy released from the analysis is 1.75 × 1017J, which is of the same order of magnitude as the USGS-observed radiated seismic energy of 1.9 × 1017Nm (J). The strain energy method is independent of seismic methods for determining the energy released during a large earthquake. The analysis shows that although the energy release is concentrated in the epicentral region, about 12% of the total energy was released throughout the Japanese islands at distances greater than 500 km west of the epicenter. Our results also show that outside the epicentral region, the strainenergy was concentrated along known tectonic zones throughout Japan.
基金National Development and Programming Project for Key Basic Researches (95-13-03-07).
文摘In this paper, GPS observations during 1998 to 1999 at fiducial stations in the Crustal Movement Observation Network of China (CMONOC) and GPS observation data processing with Bernese Software are briefly introduced. The processed results of crustal movement in the network during the period from early September 1998 to early July 1999, including the displacements at each fiducial station and strains in different part of the network, are discussed in detail. During the above mentioned period of observations, the eastern part of China was relatively stable. In contrast, the southwest part of China moved northwards about 17 mm with a dominant compression in NNE; the northwestern part of China moved northwestwards about 11 mm; and the Yunnan area moved southwards about 14 mm. The North-South seismic belt in the middle part of China is a belt of strong shear deformation. The maximum principal strain in the network is 2.9×10-8. The observation result shows that the northward push by the Indian Plate has still played the dominant role in the crystal movement in China.
基金supported by the National Natural Science Foundation of China (Project 41730212)the Basic Research Project of the Institute of Earthquake Forecasting, China Earthquake Administration (Grant No.2017IES0102, 2016IES0201)
文摘We analyzed 360 permanent and campaign GPS data from 1999 to 2017 in the southern Sichuan-Yunan block, and obtained crustal horizontal deformation in this region.Then, we derived the strain rate using a multi-scale spherical wavelet method.Results reveal a complex pattern of tectonic movement in the southern Sichuan-Yunnan block.Compared to the stable Eurasian plate, the maximum rate of the horizontal deformation in the southern Sichuan-Yunnan block is approximately 22 mm/a.The Xiaojiang fault shows a significantly lower deformation—a left-lateral strike-slip movement of 9.5 mm/a.The Honghe fault clearly shows a complex segmental deformation from the north to south.The northern Honghe fault shows 4.3 mm/a right strike-slip with 6.7 mm/a extension; the southern Honghe fault shows 1.9 mm/a right strike-slip with 1.9 mm/a extension; the junction zone in the Honghe and Lijiang–Xiaojinhe faults shows an obvious clockwise-rotation deformation.The strain calculation results reveal that the maximum shear-strain rate in this region reaches 70 nstrain/a, concentrated around the Xiaojiang fault and at the junction of the Honghe and Lijiang–Xiaojinhe faults.We note that most of the earthquakes with magnitudes of 4 and above that occurred in this region were within the high shear strain-rate zones and the strain rate gradient boundary zone, which indicates that the magnitude of strain accumulation is closely related to the seismic activities.Comparison of the fast shear-wave polarization direction of the upper-crust with the upper-mantle anisotropy and the direction of the surface principal compressive strain rate obtained from the inversion of the GPS data reveals that the direction of the surface principal compressive strain is basically consistent with the fast shear-wave polarization direction of the upper crust anisotropy, but different from the polarization direction of the upper mantle.Our results support the hypothesis that the principal elements of the deformation mechanism in the southern Sichuan-Yunnan block are decoupling between the upper and lower crust and ductile flow in the lower crust.
基金The Development and Planning Project of National Important Base Research on the Mechanism and Forecast for Continental Strong Earthquake (G19980407).
文摘The sub-regions are divided for the seismicity of the Chinese mainland based on the hypothesis of the active crustal blocks and the division of the active boundaries. On this result, the seismicity of each active crustal blocks are studied by calculating the accumulated and released strain of the earthquakes based on strain accumulating and releasing model, and the different seismicity stages of the sub-regions are discussed basically. Finally we have discussed the premise of the model application and the potential problems of the model results.
基金National Natural Science Foundation of China (40374011) and Joint Seismological Foundation of China (1040037).
文摘Borehole strain observation is playing an increasingly important role in the study on the crustal movements. It has been used by many countries such as China, USA, Japan, Peru, Australia, South Africa, Iceland and Italy, in re- search fields of plate tectonics, earthquake, volcanic eruption, dam safety, oil field subsidence, mining collapse and so on. Borehole strainmeter has been improved rapidly and tends to get more and more components included in one probe. Based on observations by this kind of instruments, studies on seismic strain step, slow earthquake, earthquake precursor and volcanic eruption forecasting have made remarkable achievements. In the coming years, borehole strain observation is going to become one major geodetic means, together with GPS and InSAR.
基金Supported by the projects of 95-04-07-03-04 and (94) 1-D1 of China Seismological Bureau, China.
文摘In the paper, the current strain field and stress field in Chinese continent have been discussedbased on the processed data from two GPS campaigns of national GPS network carried out inthe years of 1994 and 1996. With a principal compressional strain direction of NNE, thewestern and castern parts of Qinghai-Xizang subplate are dominated by extensional straiu andthe central Part by compressional strain. Along the southwestern segment of southeastern partof Qinghai-Xizang subplate, i. e. Yunnan area, the princiPal compressional strain direction isNW and the compressional strain is equivalent to the extensional strain in magnitude. Theprincipal compressional strain of Xinjiang subplate is mainly NNE and NE with a difference inthe strain magnitude. The principal compressional strain in North China subplate is quite effective in NE and nearly EW directions with differences along some segments. However, thecompressional strain is corresponding to the extensional strain in magnitude in most areas.
基金the Program of the Science and Technology Commission of Ningxia Hui Autonomous Region and Joint Foundation of Seismological Science(197043).
文摘GPS observation network is deployed in the central part of Ningxia, which is the juncture of the Alxa block, Ordos block and Qinghai-Xizang (Tibet) block. Using the data of five phases of repeated survey sine 1996, the current state of crustal movement in the central part of Ningxia is analyzed. From the result, we can know the following. (1) In the period from Dec. 1996 to May 1999, the central part of Ningxia had the phenomenon of left-lateral movement about the west margin of Ordos (measuring station P2) and the Lingwu fault on the east of the Yinchuan basin displayed the mode of left-lateral reverse strike slip movement. In that region, the direction of the principal stress field was NNE-SSW (with an azimuth of 29.8?; the central part to the south of the measuring station P2 displaced eastward; the vertical deformation was obviously greater than the horizontal deformation in order of magnitude; the Yinchuan basin and Qinghai-Xizang (Tibet) block were in a state of rising; the measuring station P1 in the hinterland of Ordos showed a trend of subsiding year by year; and there may be a hidden fault to exist between the measuring points P3 and P4. (2) About one year before the occurrence of moderately strong earthquakes in the vicinity of the measuring region, deformation anomalies and abnormal changes of principal stress direction can be observed by the GPS measuring stations in that region; before moderately strong earthquakes near the measuring region and before strong earthquakes in adjacent regions, the simulated GPS deformation vector field ofthat region can betoken the approximate position of the coming earthquake. These results can be regarded as the eigenvalues of earthquake prediction for consideration.
基金State Key Basic Development and Programming Project Mechanism and Prediction of Continental Strong Earthquakes (G1998040703) Joint Seismological Science Foundation of China (603001).
文摘Through numerical simulation for GPS data, aseismic negative dislocation model for crustal horizontal movement during 1999~2001 in the northeast margin of Qinghai-Xizang block is presented, combined with the spatial distribution of apparent strain field in this area, the characteristics of motion and deformation of active blocks and their boundary faults, together with the place and intensity of strain accumulation are analyzed. It is shown that: a) 9 active blocks appeared totally clockwise motion from eastward by north to eastward by south. Obvious sinistral strike-slip and NE-NEE relative compressive motion between the blocks separated by Qilianshan-Haiyuan fault zone was discovered; b) 20 fault segments (most of them showed compression) locked the relative motion between blocks to varying degrees, among the total, the mid-east segment of Qilianshan fault (containing the place where it meets Riyueshan-Lajishan fault) and the place where it meets Haiyuan fault and Zhuanglanghe fault, more favored accumulation of strain. Moreover, the region where Riyueshan-Lajishan fault meets north boundary of Qaidam block may have strain accumulation to some degree. c) Obtained magnitude of block velocities and locking of their boundaries were less than relevant results for observation in the period of 1993~1999.