2014年山西平遥ML4.1地震前后重力场变化特征分析*
贾宇鹏1,秦建增1,李 真1,黎哲君2,檀玉娟1,冯建林1

(1.中国地震局地球物理勘探中心,河南 郑州 450002; 2.安徽省地震局,安徽 合肥 230031)

重力场; 联合平差; 动态变化; 平遥地震

Analysis on Dynamic Variation Characteristic of Gravity Field before and after Pingyao MS4.1 Earthquake in 2014
JIA Yu-peng1,QIN Jian-zeng1,LI Zhen1,LI Zhe-jun2,TAN Yu-juan1,FENG Jian-lin1

(1.Geophysical Exploration Center,CEA,Zhengzhou 450002,Henan,China)(2.Anhui Earthquake Administration,Hefei 230031,Anhui,China)

gravity field; combined adjustment; dynamic variation; Pinyao MS4.1 earthquake

备注

利用2012～2014年山西省绝对重力和流动重力观测资料,平差计算得到该时间段重力场变化值,分析区域重力场演化特征与2014年4月平遥MS4.1地震的关系。研究发现:(1)地震发生前研究区域出现了区域性的重力异常变化,在震中附近产生局部重力异常变化,形成了与活动断裂走向基本一致的重力变化高梯度带,这可能预示着与地震发生相关的构造运动或应力增强作用。(2)地震前后研究区重力场累积变化表现为应力场增强—持续增强—局部运动受阻超过临界值—能量突然释放,震后重力场变化恢复到平稳状态。

Using the observation data of absolute and flow gravity measurements in Shanxi region from 2012 to 2014,we obtained gravity field and its dynamic variations by adjustment,and analyzed the spatial-temporal evaluation of the regional gravity field and their relationship to Pingyao MS4.1 earthquake.The research result mainly shows that:(1)Before Pingyao MS4.1 earthquake,there appeared the regional gravity anomaly in the study region and the local gravity anomaly near the epicenter.The high gradient belt of gravity change formed in accordance with the strike of the active tectonic fault,which could predict the tectonic activity or stress enhancing related with the preparation and occurrence of the earthquake.(2)Before and after the earthquake,the patterns of the gravity field accumulation variation appeared the following process in the study area:the regional stress field strengthened first,then continued to strengthen,and the local movement of it was locked somewhere,the earthquake came about during the energy exceeded the critical value.Finally,the gravity field change was back to the steady state after the earthquake.