2021年西藏比如6.1级地震前重力变化特征研究

Study on Gravity Variation before the 2021 Biru 6.1 Earthquake in Tibet Plateau

摘要:

利用青藏高原地区2015—2020年期间流动重力观测资料,研究2021年3月19日比如6.1级地震前重力变化特征,结果表明:①本次地震前约3年的重力图像中出现穿过震中区的SN向重力变化梯度带,其形态和持续时间与现有典型指标一致,表明重力变化较为清晰地反映了本次地震孕育过程中所引起的重力异常信号;②实测重力场变化与正断型断层位错引起的重力变化在形态上基本一致,结合本次比如6.1级地震的震源机制以正断为主,推测羌塘块体EW向拉伸运动为本次地震的发震背景。

Abstract:

By using mobile gravity observation data in the Tibet Plateau during 2015-2020,the gravity variation characteristics before the Biru 6.1 earthquake on March 19,2021 was studied. The results show that:① the high gradient zone along North-South direction,which is across the epicenter and in consistent with the typical gravity anomaly characteristics,has been observed in the gravity variation images of about 3 years before the earthquake. This indicates that the sign of gravity anomaly caused by the earthquake preparation has been detected. ② The observed gravity variations are basically consistent with the gravity variations caused by the dislocation of a normal fault. Considering the focal mechanism of this earthquake is mainly normal fault,the East-West stretching movement of Qiangtang block may be the background of this earthquake occurrence.