Rupture process of 12 February 2014, Yutian M(w)6. 9 earthquake and stress change on nearby faults

On February 12 2014,an Ms7.3earthquake hit Yutian,Xinjiang,the epicenter is at the intersection of Karakax fault and Gonggacuo fault.Earthquake triggering theory indicates that Coulomb stress on nearby faults will change because of crustal coseismic slip after earthquake,and it will affect earthquake potential risk.In this paper,we estimate focal mechanism and rupture process with far field seismic wave data,and calculate coseismic stress change on nearby faults around epicenter.The purpose is to discuss Coulomb stress change and seismic potential hazard on these faults caused by Yutian earthquake.After the earthquake,we download seismic far field wave data of which epicenter is between 30°to 90°from IRIS.We select27 high SNR(signal to noise ratio)seismic record to make theoretical seismogram.We use generalized ray theory to get synthetic seismic wave map,and sub fault parameter inverse process is based on simulated annealing algorithms.In the way of changing fault parameter to fit actual and synthetic wave form,optimum solution of every sub fault is found.Based on fault rupture inversion model and infinite elastic half space theory,we calculate Coulomb stress change on nearby faults caused by the earthquake.The inversion results show that source depth of earthquake is 10 km,dip angle is 71.9°,largest coseismic displacement is 210 cm.Seismic moment is 2.91×1019 N·m,the main seismic energy is released in former 10 second.Aftershocks are mainly distributed in three regions:north Pulu fault,east Karakax fault and centre Gonggacuo fault.Stress increased significantly on western segment of Altyn fault,central part of Pulu fault,eastern segment of Karakax fault and central segment of Gonggacuo fault.Among them the largest stress change is 0.05 MPa on Karakax fault and 0.04 MPa on Gonggacuo fault.Former research shows that,Coulomb stress change caused by earthquake larger than 0.01 MPa will dramatically increase seismic risk on faults.In our research,stress change on Pulu fault,Gonggacuo fault and Karakax fault exceed triggering threshold,so all these three faults have seismic risk.In the near future seismic potential hazard on these faults should be closely monitored.In the past 6years,3 moderately strong earthquakes happen in the study area,epicenters migrate from Gonggacuo fault to Altyn fault,from southwest to northeast.Though stress change on Altyn fault is much lower,in consideration of 9mm·a-1 slip rate,seismic risk on Altyn fault should cause enough attention.