芦山地震、鲁甸地震、康定地震前后三岔口地区地壳形变异常特征分析

利用三岔口地区GPS、重力、跨断层观测资料，分析2013年芦山7.0级地震、2014年鲁甸6.5级地震及康定6.3级地震前后四川地壳形变异常分布及动态图像特征。结果显示：1)2013~2014年三岔口地区几次强震前，四川地壳形变资料先后不同程度地出现群体性中、短期前兆异常，其中跨断层形变以直接前兆的形式显现出短期异常，地震发生在异常结束后的1个月内，对强震发生时间的预测具有一定的指示意义； 2)短期异常突出点分布在距震中200 km左右，异常点与强震发生地点属于同一活动构造体系；3)强震相继发生在相对重力异常区内、与跨断层中等异常幅值平行的其他断层附近以及有异常断层交汇部位，对强震发生地点的预测具有一定的指示意义。几次中强震的发生表明，2013~2014年巴颜喀拉块体向南东的带动作用使三岔口地区敏感断层活动加速，在加速的过程中其高应力积累区“失稳”并发生错动，导致脆性岩层产生破裂，从而以强震的形式释放长期积累的能量。

Analyzing Crust Deformation Anomaly in Divergence Area before and after Lushan,Ludian and Kangding Earthquakes

Using observation data of GPS, gravity and across fault in divergence area, we analyze crustal deformation anomaly distribution and dynamic image characteristics in Sichuan province before and after the Lushan 7.0, Ludian 6.5 and Kangding 6.3 earthquakes. The results show: 1) before the earthquakes during 2013 and 2014 in divergence area, the crustal deformation data in Sichuan province presents group mid-term and short-term precursory anomalies in different degrees, including cross fault deformation that appears as a short-term anomaly in the form of direct precursors, and that earthquakes occurred within one month from the end of the anomaly, which has instructive significance in strong earthquake occurrence time forecasting; 2) a prominent short-term anomaly point located about 200 kilometers from the epicenter, earthquake location and anomaly belong to the same tectonic system; 3) strong earthquakes occurred in the relative gravity anomaly zone and in faults which are parallel to or intersect the fault,which has cross fault secondary anomaly amplitude, which has instructive significance in strong earthquake location forecasting. These several moderate-strong earthquakes show that, during 2013 and 2014 the south-eastern drive function of the Bayan Har Block acceleratedsensitive fault activity in the divergence area; in the process of accelerating, the stress accumulation area ruptured because of the instability, which further resulted in brittle rock burst, thus releasing long-term accumulated energy in strong earthquakes.