The mainshock of April 20,2013 Sichuan Lushan MS7.0 earthquake was relocated using a 3-D velocity model.Double difference algorithm was applied to relocate aftershock sequences of Lushan earthquake.The locations of 24...The mainshock of April 20,2013 Sichuan Lushan MS7.0 earthquake was relocated using a 3-D velocity model.Double difference algorithm was applied to relocate aftershock sequences of Lushan earthquake.The locations of 2405 aftershocks were determined.The location errors in E-W,N-S and U-D direction were 0.30,0.29 and 0.59 km on average,respectively.The location of the mainshock is 102.983°E,30.291°N and the focal depth is 17.6 km.The relocation results show that the aftershocks spread approximately 35 km in length and 16 km in width.The dominant distribution of the focal depth ranges from 10 to 20 km.A few earthquakes occurred in the shallow crust.Focal depth profiles show fault planes dip to the northwest,manifested itself as a listric thrust fault.The dip angle is steep in the shallow crust and gentle in the deep crust.Although the epicenters of aftershocks distributed mainly along both sides of the Shuangshi-Dachuan fault,the seismogenic fault may be a blind thrust fault on the eastern side of the Shuangshi-Dachuan fault.Earthquake relocation results reveal that there is a southeastward tilt aftershock belt intersecting with the seismogenic fault with y-shape.We speculate it is a back thrust fault that often appears in a thrust fault system.Lushan earthquake triggered the seismic activity of the back thrust fault.展开更多
Moment tensor solutions of 88 earthquakes were determined by using the broadband waveform data recorded in six stations within 450 km around the Wenchuan Earthquake sequence by means of the time domain moment tensor i...Moment tensor solutions of 88 earthquakes were determined by using the broadband waveform data recorded in six stations within 450 km around the Wenchuan Earthquake sequence by means of the time domain moment tensor inversion method.It was found that the type of the focal mechanism solution is characteristic of obvious spatial segmentation.There are six segments along the main rupture zone from southwest to northeast,where initially the focal mechanism is of main thrust type,finally of main right-lateral strike-slip type and between these two areas there is a transition zone characterized in multiple types of focal mechanisms appearing in turn.Earthquakes of left-lateral strike-slip type perpendicular to the main rupture zone occurred near Xiaoyudong Town.The stress field of each segment is inversed by means of the FMSI program,and it was found that,along the main rupture zone from southwest to northeast,the direction of the maximum principal stress is gradually changing from near EW to NW-SE,and finally changing back to near EW.展开更多
基金supported by the National Natural Science Foundation of China(41074068)the National Science and Technology Support Program(2012BAK19B01)China National Special Fund for Earthquake Scientific Research in Public Interest(201308013)and Scientific Investigation of April 20,2013 M7.0 Lushan,Sichuan Earthquake
文摘The mainshock of April 20,2013 Sichuan Lushan MS7.0 earthquake was relocated using a 3-D velocity model.Double difference algorithm was applied to relocate aftershock sequences of Lushan earthquake.The locations of 2405 aftershocks were determined.The location errors in E-W,N-S and U-D direction were 0.30,0.29 and 0.59 km on average,respectively.The location of the mainshock is 102.983°E,30.291°N and the focal depth is 17.6 km.The relocation results show that the aftershocks spread approximately 35 km in length and 16 km in width.The dominant distribution of the focal depth ranges from 10 to 20 km.A few earthquakes occurred in the shallow crust.Focal depth profiles show fault planes dip to the northwest,manifested itself as a listric thrust fault.The dip angle is steep in the shallow crust and gentle in the deep crust.Although the epicenters of aftershocks distributed mainly along both sides of the Shuangshi-Dachuan fault,the seismogenic fault may be a blind thrust fault on the eastern side of the Shuangshi-Dachuan fault.Earthquake relocation results reveal that there is a southeastward tilt aftershock belt intersecting with the seismogenic fault with y-shape.We speculate it is a back thrust fault that often appears in a thrust fault system.Lushan earthquake triggered the seismic activity of the back thrust fault.
基金Supported by the National Key Project of Scientific and Technical Supporting Programs Funded by Ministry of Science & Technology of China (Grant No.2008BAC38B02 and 2006BAC01B02)National Department Public Benefit Research Foundation (Grant No.200708026)
文摘Moment tensor solutions of 88 earthquakes were determined by using the broadband waveform data recorded in six stations within 450 km around the Wenchuan Earthquake sequence by means of the time domain moment tensor inversion method.It was found that the type of the focal mechanism solution is characteristic of obvious spatial segmentation.There are six segments along the main rupture zone from southwest to northeast,where initially the focal mechanism is of main thrust type,finally of main right-lateral strike-slip type and between these two areas there is a transition zone characterized in multiple types of focal mechanisms appearing in turn.Earthquakes of left-lateral strike-slip type perpendicular to the main rupture zone occurred near Xiaoyudong Town.The stress field of each segment is inversed by means of the FMSI program,and it was found that,along the main rupture zone from southwest to northeast,the direction of the maximum principal stress is gradually changing from near EW to NW-SE,and finally changing back to near EW.
