湖北秭归4.5级和4.1级地震前的流动重力变化

处理分析2016～2018年三峡流动重力测网资料，获得2016-03～2018-09共11幅差分和累积重力场变化图像，并结合2018-10-11发生在湖北秭归的4.5级和4.1级地震，分析震前重力场变化特征。结果表明：1）2017年以来，震中区重力场变化经历了从先减小后增大到震前趋缓的过程。2）2 a累积重力场变化显示，新华-龙王冲和高桥断裂带两端重力场变化差异增大，可能与本次地震的孕育有关。3）只要测网网格距合理、数据处理得当，区域流动重力测网对4.0级小震前的重力场变化具有潜在的监测能力。

Gravity Changes before the M4.5 and M4.1 Earthquakes in Zigui County

The repeated gravity data of the Three Gorges gravity network are processed and analyzed. 11 differential and cumulative gravity change maps from March 2016 to September 2018 are obtained. The characteristics of gravity changes before the Zigui M4.5 and M4.1 earthquakes on October 11, 2018 are analyzed. The results show that: 1) since 2017, the gravity field of the epicenter region decreases, then increases, then decreases slightly before the earthquake occurs; 2) the two-year cumulative gravity changes show that gravity changes increase along the Xinhua-Longwangchong and Gaoqiao fault areas, which may be related to the preparation of these earthquakes; 3) as long as the observation network grid distance is reasonable and the data are properly processed, the regional mobile gravity survey network can give us potential detection capability for the change of gravity field before small earthquakes of magnitude 4.0.