台湾集集7.6级强震前粤东地区的重力中短期异常

Gravity Anomaly in Eastern Guangdong before Jiji M7.6 Earthquake in 1999

基于广东东部地区流动重力观测资料,分析了1999年台湾集集7.6级地震前后重力场的时空动态演化过程,发现1996年起出现的群体性重力测值偏离长趋势的变化,可视为7.6级地震前中期异常的开始,而1998年中出现的反向变化则是中期异常向短期异常的转折。作为强震前的远场重力异常,其时间、空间变化表现出的不一致和非均匀性变化形态,可能主要与测区内不同断层在区域应力场和震源应力场共同作用下产生的局部形变不同有关。

Based on the data of mobile gravity survey in Eastern Guangdong after 1988, the temporal and spatial evolution of gravity field before and after Jiji M7.6 earthquake in 1999 are studied. The anomalous variation of gravity field from 1996 to 1999 were the precursor of far field of stress in Southeast China before Jiji M7.6 earthquake. Those variation of gravity, which appeared in group and deviated normal trend in 1996, may be a beginning of medium-term anomaly for 7.6 earthquake. The another reverse variation in 1998 were the transition of anomaly from medium-term to short-term and the variation may be a mark of anomalous progression before strong earthquake. Dynamic temporal and spatial evolution of gravity as the far-field gravity anomaly is more closely related with tectonic motion, its inhomogeneous and different variations in temporal and spatial evolution are mainly related to local deformation that resulted from the action of regional and focal stress field.