Stress Reorientation by Earthquakes Near the Ganzi-Yushu Strike-Slip Fault and Interpretation with Discrete Element Modelling

Earthquakes are generally known to alter the stress field near seismogenic faults. Observations using YRY-four-gauge borehole strainmeters within Yushu (YSH) Ganzi-Yushu fault in eastern Tibetan Plateau shows that azimuth variation of maximum horizontal (SH) first decreased and then increased substantially when earthquakes occurred during measurement period from January 1, 2009 December 31, 2018. In this period, 38 (M ≥ 3) were detected SH orientation showed a drastic change after 2010 Ms 7.3 mainshock. We present discrete element modelling Particle Flow Code 2D (PFC2D) simulate dynamic rupturing process use results for interpretation reorientation. The reveals dilatation compression quadrants formed around strike-slip model, resulting different spatiotemporal changes (Δθ). value Δθ sharp drop at time coseismic slip, approaches slowly an asymptotic value. quadrants, drops by increases sharply finally reaches stable modelled slip agrees with in-situ observations YSH It is also found that, decreases increasing distance source. effect geometry host rock properties on Δθ, structural complexity off-fault damage have significant impact alteration