The 12 May 2008 Wenchuan Ms8.0 earthquake produced surface displacements along the causative fault,the Yingxiu-Beichuan Fault,which are up to several meters near the fault.Because of the large gradient,satellite synth...The 12 May 2008 Wenchuan Ms8.0 earthquake produced surface displacements along the causative fault,the Yingxiu-Beichuan Fault,which are up to several meters near the fault.Because of the large gradient,satellite synthetic aperture radar(SAR) interferometric data are strongly incoherent;the usual SAR interferometry method does not allow such displacements to be measured.In the present study,we employed another approach,the technique based on pixel offset tracking,to solve this problem.The used image data of six tracks are from the Advanced Land Observing Satellite,Phased Array type L-band Synthetic Aperture Radar(ALOS/PALSAR) dataset of Japan.The results show that the entire surface rupture belt is 238 km long,extending almost linearly in a direction of 42° north-east.It is offset left laterally by a north-west-striking fault at Xiaoyudong,and turns at Gaochuan,where the rupture belt shifts toward the south by 5 km,largely keeping the original trend.In terms of the features of the rupture traces,the rupture belt can be divided into five sections and three types.Among them,the Beichuan-Chaping and Hongkou-Yingxiu sections are relatively complex,with large widths and variable traces along the trend.The Pingtong-Nanba and Qingping-Jingtang sections appear uniform,characterized by straight traces and small widths.West of Yingxiu,the rupture traces are not clear.North of the rupture belt,surface displacements are 2.95 m on average,mostly 2-3.5 m,with 7-9 m the maximum near Beichuan.South of the rupture belt,the average displacement is 1.75 m,dominated by 1-2 m,with 3-4 m at a few sites.In the north,the displacements in the radar line of sight are of subsidence,and in the south,they are uplifted,in accordance with a right-slip motion that moves the northern wall of the fault to the east,and the southern wall to the west,respectively.Along the Guanxian-Jiangyou Fault,there is a uplift zone in the radar line of sight,which is 66 km long,1.5-6 km wide,and has vertical displacements of approximately 2 m,but no observable rupture traces.展开更多
On 21 March 2008,a Ms7.3 earthquake occurred at Quickbird,Yutian County,Xinjiang.We attempt to reveal the features of the causative fault of this shock and its coseismic deformation field.Our work is based on analysis...On 21 March 2008,a Ms7.3 earthquake occurred at Quickbird,Yutian County,Xinjiang.We attempt to reveal the features of the causative fault of this shock and its coseismic deformation field.Our work is based on analysis and interpretation to high-resolution satellite images as well as differential interferometric synthetic aperture radar(D-InSAR) data from the satellite Envisat SAR,coupled with seismicity,focal mechanism solutions and active tectonics in this region.The result shows that the 40km-long,nearly NS trending surface rupture zone by this event lies on a range-front alluvial platform in Qira County.It is characterized by distinct linear traces and simple structure with 1-3-m-wide individual seams and maximum 6.5m width of a collapse fracture.Along the rupture zone many secondary fractures and fault-bounded blocks are seen,exhibiting remarkable extension.The coseismic deformation affected a large area 100×100km2.D-InSAR analysis indicates that the interferometric deformation field is dominated by extensional faulting with a small strike-slip component.Along the causative fault,the western wall fell down and the eastern wall,that is the active unit,rose up,both with westerly vergence.Because of the big deformation gradients near the seismogenic fault,no interference fringes are seen on images,and what can be determined is a vertical displacement 70cm or more between the two fault walls.According to the epicenter and differential occurrence times from the National Earthquake Information Center,China Earthquake Network Center,Harvard and USGS,it is suggested that the seismic fault ruptured from north to south.展开更多
Based on the working principle of satellite radars, the earthquake deformation field measured by interferometric synthetic aperture(InSAR) is the projection of ground displacement associated with the seismogenic fault...Based on the working principle of satellite radars, the earthquake deformation field measured by interferometric synthetic aperture(InSAR) is the projection of ground displacement associated with the seismogenic fault in the line of sight(LOS) of the satellite. However, LOS projections are complex, and are not only related to the ascending/descending modes and incidence angles of SAR data, but also related to the strike and motion senses of the fault. Even for the same earthquake, the LOS deformation derived from different ascending/descending data can be almost identical in one case, but quite different in another case, which makes the interpretation of InSAR seismic deformation and its comparison with field observations difficult. In this study, we undertook a quantitative analysis of the relationships between LOS observation sensitivity of InSAR and fault strike, fault motion sense, and ascending/descending modes, as well as 3D deformation fields. We studied the features and differences of the LOS deformation fields in different types of earthquakes using ascending/descending modes, with a particularly detailed analysis of the relations for a strikeslip type of earthquake. We also summarized the characteristics of LOS deformation fields of faults with different strikes and optimal observational data modes. Taking the strike-slip Yushu earthquake and the normal Gaize event as examples, we used SAR data of the ascending/descending modes to verify the results of quantitative calculations. These analyses will not only provide a more reasonable interpretation of InSAR seismic deformation fields and but also help understand the differences of seismic deformation fields revealed by data with different observational modes, therefore promoting the application of InSAR technology in seismology.展开更多
Objective Nowadays,high-resolution remote sensing technology has brought new changes to surveys of earthquakes,and the quantitative study of seismic faults based on this technology has become a trend in the world (Bar...Objective Nowadays,high-resolution remote sensing technology has brought new changes to surveys of earthquakes,and the quantitative study of seismic faults based on this technology has become a trend in the world (Barzegari et al.,2017).An Mw 7.2 earthquake occurred in Yutian of Xinjiang on the western end of the Altyn Tagh fault on March 21 st,2008.It is difficult to access this depopulated zone because of the high altitude and only 1-2 months of snowmelt.This study utilized high-resolution remote sensing to examine the geometric and kinematic characteristics of the surface rupture zone produced by this event.It will cast new light on the application of high-resolution remote sensing to the quantitative research of earthquakes.展开更多
基金supported by the State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration(CEA) (no. LED2010A02,LED2008A06)
文摘The 12 May 2008 Wenchuan Ms8.0 earthquake produced surface displacements along the causative fault,the Yingxiu-Beichuan Fault,which are up to several meters near the fault.Because of the large gradient,satellite synthetic aperture radar(SAR) interferometric data are strongly incoherent;the usual SAR interferometry method does not allow such displacements to be measured.In the present study,we employed another approach,the technique based on pixel offset tracking,to solve this problem.The used image data of six tracks are from the Advanced Land Observing Satellite,Phased Array type L-band Synthetic Aperture Radar(ALOS/PALSAR) dataset of Japan.The results show that the entire surface rupture belt is 238 km long,extending almost linearly in a direction of 42° north-east.It is offset left laterally by a north-west-striking fault at Xiaoyudong,and turns at Gaochuan,where the rupture belt shifts toward the south by 5 km,largely keeping the original trend.In terms of the features of the rupture traces,the rupture belt can be divided into five sections and three types.Among them,the Beichuan-Chaping and Hongkou-Yingxiu sections are relatively complex,with large widths and variable traces along the trend.The Pingtong-Nanba and Qingping-Jingtang sections appear uniform,characterized by straight traces and small widths.West of Yingxiu,the rupture traces are not clear.North of the rupture belt,surface displacements are 2.95 m on average,mostly 2-3.5 m,with 7-9 m the maximum near Beichuan.South of the rupture belt,the average displacement is 1.75 m,dominated by 1-2 m,with 3-4 m at a few sites.In the north,the displacements in the radar line of sight are of subsidence,and in the south,they are uplifted,in accordance with a right-slip motion that moves the northern wall of the fault to the east,and the southern wall to the west,respectively.Along the Guanxian-Jiangyou Fault,there is a uplift zone in the radar line of sight,which is 66 km long,1.5-6 km wide,and has vertical displacements of approximately 2 m,but no observable rupture traces.
基金supported by the National Natural Science Foundation of China(40940020,40874006)National Key Laboratory of Earthquake Dynamics(LED2010A02,LED2008A06)
文摘On 21 March 2008,a Ms7.3 earthquake occurred at Quickbird,Yutian County,Xinjiang.We attempt to reveal the features of the causative fault of this shock and its coseismic deformation field.Our work is based on analysis and interpretation to high-resolution satellite images as well as differential interferometric synthetic aperture radar(D-InSAR) data from the satellite Envisat SAR,coupled with seismicity,focal mechanism solutions and active tectonics in this region.The result shows that the 40km-long,nearly NS trending surface rupture zone by this event lies on a range-front alluvial platform in Qira County.It is characterized by distinct linear traces and simple structure with 1-3-m-wide individual seams and maximum 6.5m width of a collapse fracture.Along the rupture zone many secondary fractures and fault-bounded blocks are seen,exhibiting remarkable extension.The coseismic deformation affected a large area 100×100km2.D-InSAR analysis indicates that the interferometric deformation field is dominated by extensional faulting with a small strike-slip component.Along the causative fault,the western wall fell down and the eastern wall,that is the active unit,rose up,both with westerly vergence.Because of the big deformation gradients near the seismogenic fault,no interference fringes are seen on images,and what can be determined is a vertical displacement 70cm or more between the two fault walls.According to the epicenter and differential occurrence times from the National Earthquake Information Center,China Earthquake Network Center,Harvard and USGS,it is suggested that the seismic fault ruptured from north to south.
基金jointly supported by projects of the National Key Laboratory for Earthquake Dynamics (LED2013A02,LED2015A03)the National Natural Science foundation of China (41374105)
文摘Based on the working principle of satellite radars, the earthquake deformation field measured by interferometric synthetic aperture(InSAR) is the projection of ground displacement associated with the seismogenic fault in the line of sight(LOS) of the satellite. However, LOS projections are complex, and are not only related to the ascending/descending modes and incidence angles of SAR data, but also related to the strike and motion senses of the fault. Even for the same earthquake, the LOS deformation derived from different ascending/descending data can be almost identical in one case, but quite different in another case, which makes the interpretation of InSAR seismic deformation and its comparison with field observations difficult. In this study, we undertook a quantitative analysis of the relationships between LOS observation sensitivity of InSAR and fault strike, fault motion sense, and ascending/descending modes, as well as 3D deformation fields. We studied the features and differences of the LOS deformation fields in different types of earthquakes using ascending/descending modes, with a particularly detailed analysis of the relations for a strikeslip type of earthquake. We also summarized the characteristics of LOS deformation fields of faults with different strikes and optimal observational data modes. Taking the strike-slip Yushu earthquake and the normal Gaize event as examples, we used SAR data of the ascending/descending modes to verify the results of quantitative calculations. These analyses will not only provide a more reasonable interpretation of InSAR seismic deformation fields and but also help understand the differences of seismic deformation fields revealed by data with different observational modes, therefore promoting the application of InSAR technology in seismology.
基金supported by the National Natural Science Foundation of China (grants No. 41461164002 and 41631073)
文摘Objective Nowadays,high-resolution remote sensing technology has brought new changes to surveys of earthquakes,and the quantitative study of seismic faults based on this technology has become a trend in the world (Barzegari et al.,2017).An Mw 7.2 earthquake occurred in Yutian of Xinjiang on the western end of the Altyn Tagh fault on March 21 st,2008.It is difficult to access this depopulated zone because of the high altitude and only 1-2 months of snowmelt.This study utilized high-resolution remote sensing to examine the geometric and kinematic characteristics of the surface rupture zone produced by this event.It will cast new light on the application of high-resolution remote sensing to the quantitative research of earthquakes.
