Stepover Rupture of the 2014 Mw 7.0 Yutian, Xinjiang, Earthquake

Multiple parallel strike-slip faults cut through the Ashikule basin, Xinjiang. The Ashikule basin was struck by an M-w 7.0 earthquake on 12 February 2014. To distinguish the causative fault from these parallel faults, the rupture process of the earthquake was investigated. Here, we first jointly backprojected teleseismic P wavetrains at Alaska, European, and Australian seismic networks to obtain a rupture model. Next, a kinematic finite-fault model was derived by inverting teleseismic P waves recorded at the Global Seismographic Network. The two rupture models, together, show that that the earthquake first bilaterally ruptures the northwestward-dipping south Xiaoerkule fault and then steps over to another parallel Xiaoerkule-Ashikule fault. The fault stepover acts as a geometrical barrier during the rupture propagation. The rupture at the fault stepover bursts an energy-releasing peak in both high-and low-frequency content. The high-frequency sources are located at the edge of the shallow low-frequency asperity, which has an average stress drop of similar to 1.4 MPa. The aftershock spatial gap in the northeastern branch of the mainshock indicates that the accumulated strain energy could be all used up, inferring that the earthquake has a recurrence period of similar to 160 years.