Discrete Element Modeling of the Spatiotemporal Deflection Characteristics of the Local Stress Field of the Ganzi-Yushu Fault before the Yushu Earthquake
Regional tectonic activities alter the stress state of the crust,and tectonic earthquakes are extreme regional tectonic activities.Therefore,understanding the change in the local stress field of seismogenic faults before earthquakes occur has great significance in the characterization of fault activities.This study used the particle discrete element package PFC2D and monitoring data of the YRY-4 borehole strain gauge at the Yushu Seismic Station to simulate the spatiotemporal deflection characteristics of the maximum principal stress direction in the local stress field before the Yushu MS7.1 earthquake on April 14,2010,and the Ganzi-Yushu strike-slip fault.The results showed that the SH direction of the maximum horizontal principal stress at the Yushu station before the earthquake displayed counterclockwise deflection.The deflection gradually recovered after a certain amount of strain energy had accumulated.The change pattern of the simulated local stress direction was generally consistent with the field observation results.The variation pattern of SH differed at different positions of the fault,and the disturbance of local stress was more obvious with nearer proximity to the fault structure.The SHT located in the tensile stress concentration area and the SHP located in the compressive stress concentration area rotated simultaneously toward the boundary direction of the two areas.The deflection angle increased gradually with increasing time step.The degree of stress accumulation varied among different regions and increased with loading time.Fractures occurred at different times,with obvious spatiotemporal asynchronous effects.
万方数据
维普
