Impact of dynamic stress on aftershock triggering of the 2021 Yunnan Yangbi M_S6.4 earthquake

Based on the waveform data of IRIS teleseismic station, this paper inversed the focal rupture process of Yunnan Yangbi M_S6.4 earthquake, calculated the dynamic Coulomb rupture stress change caused by fault rupture in near field and discussed the dynamic stress triggering effect of main shock on near-field aftershock activity. The results show that the evolution process of dynamic Coulomb stress is consistent with the inversion results of source fracture characteristics, and its size distribution is also well correlated with the density of seismic sequence distribution. The static and dynamic Coulomb rupture stress produced by the main shock promote the occurrence of aftershocks, but compared with the static stress, the proportion of aftershocks located in the positive Coulomb rupture stress area is increased by 21%, and the positive and negative areas of aftershocks and dynamic Coulomb stress change have better consistency. The dynamic stress can better explain the spatial characteristics of aftershocks distribution after the earthquake. Small earthquakes cluster at 10 km perpendicular to the main trunk of the earthquake sequence, which may be caused by the dominant dynamic Coulomb fracture stress produced by the main earthquake. Quantitative analysis of the dynamic stress triggering of the main shock to the aftershock shows that within one week after the main shock, eight aftershocks receiving points bigger than M_S4.0 are triggered by the dynamic Coulomb rupture stress.