Diverse rupture processes of the 2014 Kangding, China, earthquake doublet (MW 6.0 and 5.7) and driving mechanisms of aftershocks

Abstract

An unusual earthquake doublet ruptured the high-risk middle segment of the Xianshuihe fault in November 2014, exhibiting significant variations in the rupture and aftershock characteristics. By conducting rupture kinematic inversions jointly with local broadband seismic data, strong-motion data, and coseismic InSAR data, we find diverse rupture processes of this earthquake doublet. The first event ruptured upward along the dip and bilaterally along the strike with the duration of 8.0 s, whereas the second event ruptured mainly around the hypocenter with the duration of 3.5 s. The estimated moment magnitudes of the first and second events of this earthquake doublet were MW 6.0 and MW 5.7, respectively. The further analysis of rupture model-based static and dynamic stress change suggests that the first event is likely responsible for triggering the second event. Based on the comprehensive analysis of aftershock migration features, we find complex and diverse driving mechanisms of aftershocks. Aftershocks of the first event of the earthquake doublet were likely driven by afterslip. Early aftershocks of the second event were also likely driven by afterslip; however, later aftershocks were likely driven by fluid diffusion. The revealed diverse rupture characteristics of the 2014 Kanding earthquake doublet sequence suggest the inherent strength and/or stress heterogeneities on the seismogenic faults.