Joint analysis of the 2014 Kangding, southwest China, earthquake sequence with seismicity relocation and InSAR inversion

Abstract

AbstractOver 1000 earthquakes struck the northwest of Kangding on the Xianshuihe fault in southwest China between 22 and 29 November 2014, including two largest events of Mw 5.9 and Mw 5.6. The hypocenters of 799 relocated earthquakes suggest that two independent main shock‐aftershock subsequences occurred on the Selaha and Zheduotang branches of the Xianshuihe fault, respectively. Fault slip inversion results from one interferometric synthetic aperture radar (InSAR) interferogram (26 September 2014 to 5 December 2014) show that the Mw 5.9 main shock produced a maximum slip of ~0.47 m at the depth of ~9 km. However, there is no distinct slip associated with the Mw 5.6 main shock. The InSAR determined moment is 2.36 × 1018 Nm with a rigidity of 30 GPa, equivalent to Mw 6.2, which is about twofold the total seismic moment of all the recorded earthquakes during the InSAR time span. This large discrepancy between geodetic and seismic moment estimates indicates that there was probably rapid aseismic afterslip in the 2 weeks following the Mw 5.9 main shock. The released seismic energy of this earthquake sequence is far less than the accumulated strain energy since the 1955 M earthquake on the same fault branch, which implies that the seismic risk on the Selaha‐Kangding segment of the Xianshuihe fault remains high.