2014年2月12日新疆于田M_W7.0地震源区静态库仑应力变化和地震活动率

Static Coulomb stress changes and seismicity rate in the source region of the 12 February,2014 M_W7.0 Yutian earthquake in Xinjiang,China

2014年2月12日新疆于田M_W7.0地震源区位于巴颜喀拉块体与西昆仑块体的连接部位,东西向拉张构造发育,距离2008年3月21日于田MW7.1地震震中位置约100km.根据有限断层地震破裂过程模型,计算了2008年新疆于田地震产生的静态库仑应力变化.此次地震的断层面呈北偏东方向,在断层两端出现3个应力加载区,2014年于田主震位于破裂前端的库仑应力加载区.这一结果表明,2008年于田地震可能对2014年地震事件起到了触发作用.2008和2014年新疆于田地震产生的静态库仑应力变化与余震事件的空间分布具有明显的相关性,大多数余震位于应力加载区,发生在卸载区的余震较少.静态库仑应力变化与余震序列吻合较好.2014年3月21日新疆于田地震之后40天,在北西方向发生MW5.2强余震,其震中位置的应力增量达到0.63×105Pa.通过比较,发现静态库仑应力变化和地震活动率之间具有较好的相关性.地震活动率较高的区域与静态库仑应力加载区相对应,如康西瓦断裂东段、贡嘎错断裂中段和东北段等区域.

On February 12,2014,an M_W7.0earthquake 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 M_W7.1Yutian earthquake.We investigate the Coulomb stress changes due to the 2008 earthquake and itstriggering 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 MW5.2aftershock occurred in the NW of the 2014 mainshock where the stress increases for 0.63×105Pa.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.