2020年1月19日新疆伽师MS6.4地震前后GNSS异常特征研究

2020年1月19日新疆伽师发生M S6.4地震,地震发生后,梳理了连续GNSS和流动GNSS的观测资料,发现震中附近站点运动方向与其东部站点的运动方向存在一定的差异,可能显示了震中附近区域应力震前处于失稳状态。巴楚—叶城基线挤压缩短速率快于以往,约为前期缩短速率的3倍,趋势转折时间近3年;从巴楚—乌恰基线可以看出该地震受东西向应力的作用较小。最新一期的流动GNSS结果显示,地震发生在剪应变高值向低值过渡的区域,发生在面膨胀负极值区域边缘;块体应变参数从短期变化来看,面膨胀值在增大的同时,剪应变在减小,也说明北北西向的正应力和北东东向剪应力的作用差异增大,断层的受力平衡被打破,这可能是地震发生的力学机制。

CHARACTERISTICS OF GNSS ANOMALIES BEFORE AND AFTER JIASHI M S6.4 EARTHQUAKE IN XINJIANG ON JANUARY 19TH,2020

On January 19,2020,Jiashi Earthquake with M S6.4 occurred in Xinjiang.After the earthquake,we combed the observation data of continuous GNSS and mobile GNSS.We found that there was a certain difference between the movement direction of the stations near the epicenter and that of the stations in the East,which may indicate that the regional stress near the epicenter was in a state of instability before the earthquake.From Bachu to Yecheng baseline,the compression rate of the baseline is faster than before,about three times of the previous shortening rate,and the trend turning time is nearly three years;from Bachu Wuqia baseline,it can be seen that the earthquake is less affected by the East-West stress.The results of the latest mobile GNSS show that the earthquake occurred in the area of transition from high shear strain to low shear strain,and occurred at the edge of the area of negative extreme value of surface expansion;from the short-term change of the block strain parameters,when the surface expansion value increases,the shear strain decreases,which means that the difference between the action of the north-west positive stress and the north-east shear stress increases,and the stress balance of the fault is broken,this may be the mechanical mechanism of earthquake.