湖北应城M4.9地震前重力变化

处理分析2016~2019年湖北及邻区流动重力测网资料,获得2016-09~2019-09的14幅长期和近期重力场变化图像,结合2019-12-26湖北应城M4.9地震,分析震前重力场变化特征,结果表明:1)对应城M4.9地震起控制作用的断裂为襄樊(襄阳)-广济(武穴)断裂,是正负重力变化转换带;2)应城M4.9地震重力异常变化有一个上升-下降的过程,在下降过程中发震;3)应城M4.9地震与秭归M4.5和M4.1地震一样,震前重力场异常变化持续时间较长,可能与两湖地区活动断裂活动性弱、相对运动量小、应力难以集中有关。

The Gravity Changes before the M4.9 Earthquake in Yingcheng County

We process and analyze the repeated gravimetry network data of Hubei province and its adjacent area. 14 long-term and short-term gravity change maps are obtained from Sep 2016 to Sep 2019. We analyze the gravity changes characteristics before Yingcheng M4.9 earthquake on December 26, 2019. The results show that: 1) The Xiangfan(Xiangyang)-Guangji(Wuxue) fault is related to Yingcheng M4.9 earthquake. It is in the transition zone between positive and negative gravity anomaly. 2) There is an abnormal rise and fall of gravity before the earthquake. It occurs during the fall process. 3) The earthquake pregnancy spans a long period of time, which is similar to Zigui M4.5 and M4.1 earthquakes on October 11, 2018. The similarity may be related to the fact that the activity of active faults in Hubei and Hunan province is weak; their movement amount is small and their stresses are often hard to concentrate.