Static Coulomb Stress Changes And Seismicity Rate In The Source Region Of The 2014 Mw7.0 Yutian Earthquake In Xinjiang,China

On February 12,2014,an Mw7.0 earthquake occurred in Yutian region,Xinjiang,China.The epicenter of this earthquake is located in an area linking the Bayan Har block and west Kunlun block,a region with highly developed east-west trend tension structures.This earthquake is approximately 100 km away from a previous earthquake,the 2008 Mw7.1 Yutian earthquake.The Coulomb stress changes can indicate the mutual triggering relationship between the earthquakes,the spatial distribution of the aftershocks and the seismic hazard of the surrounding active faults.Meanwhile,it may change the Seismicity rate.Therefore,we download the earthquake events from the China Earthquake Networks Center and the China Earthquake Datacenter in Xinjiang Yutian Area since 2009 with magnitude greater than mL 1.0,we investigate the Coulomb stress changes and the Seismicity rate.We investigate the Coulomb stress changes due to the 2008 earthquake and its triggering effect on the 2014 earthquake.The Coulomb stress changes caused by the two mainshocks and their effects on the subsequent aftershock sequences are also investigated.The main fracture of the 2008 earthquake extends along the NE direction.Based on the finite-sized fault model,we calculate its static Coulomb stress,which has three stress increase lobes at each ends.The 2014 Yutian earthquake is located in the increased Coulomb stress lobe of the 2008 earthquake,therefore it may be trigged by the 2008 earthquake.For both earthquakes,their aftershock distributions are correlated with their Coulomb stress changes caused by the mainshocks calculated based on their optimal orientations.We find that most of the aftershocks occurred in the increased Coulomb stress lobe,while few aftershocks occurred in the stress shadow zone.An apparent correlation is obtained between the mainshock stress changes and the observed spatial distribution of the aftershock occurrence,demonstrating the usefulness of the stress maps in predicting likely upcoming aftershock locations.An Mw5.2 aftershock occurred in the NW of the 2014 mainshock where the stress increases for 0.63 bar.We calculated the coulomb stress changes on the faults surrounding the fault zone which caused by co-seismic effects of the February 12,2014,an Mw7.0 earthquake.Theresult shows that,we find that it is increase in the middle of the Pulu fault,the middle of the Kangxiwar fault,and the EN segments of Gonggar Co fault.We used the complete data set available during 2009 to 2014 to constrain the seismicity rate change.A background seismicity rate is established using data from2009 through the Yutian mainshock.The data after the Yutian mainshock through 31 December 2014 to establish a postmainshock seismicity rate.Mc for pre-and post-2014 mainshock are 2.9 and 2.0,respectively.We calculate Z value.The observation indicates that the regions with high seismicity rate are highly correlated with regions with high Coulomb stress changes,e.g.,the eastern of the Kangxiwar fault,the middle and EN segments of Gonggar Co fault,etc.