Stress drop, earthquake aftershocks and regional stress relation based on synthetic static Coulomb failure stress model

Abstract

Coulomb failure criterion has been applied widely in the scope of earthquake science to explain earthquake interactions base on stress change, with the well-known method named Coulomb failure stress change ΔCFS). Preceding studies have showed: increase ΔCFS, depicted as positive stress lobes, has correlation with occurrence of following events. However in the calculation process, ratio between regional stress and earthquake stress drop would affect stress distribution. Based on preceding researches, earthquake stress drop with similar magnitude to regional stress, would give results positive stress lobes along and at the base of the fault. Those stress distribution, could explain events interaction and mechanism of earthquake. This work carries out synthetic modeling of static ΔCFS upon varying earthquake stress drop and regional stress using COULOMB3.3. In accord with preceding studies, the results show positive ΔCFS along the fault when stress drop is comparable to regional stress. And yet, positive ΔCFS would take place at the top and at the base of the fault, expanding to the center of the fault -where the hypocenter is assumed- as the stress drop reaching regional stress in magnitude. This could explain the separated clusters of aftershock in depth observed in some earthquakes.