宁夏地区重力场变化与2012年永宁M_S4.6地震

Gravity Field Variation in Ningxia Region and Its Relation to the 2012 Yongning M_S4.6 Earthquake

利用宁夏地区2011—2013年期间多期重力观测资料,采用中国地震局推广的LG-ADJ程序对观测资料进行平差处理,给出地震前后3年的区域重力场变化和点值变化图像。结合构造活动分析,对2012永宁4.6级地震前后宁夏地区重力异常变化进行研究。认为:2012年永宁地震前,测区重力场出现较好的中期前兆性变化图像,临震前短期异常突增,重力场在空间和量值上均出现大幅的上升变化,重力点值震前趋势下降-转折上升-加速上升-发震的变化,是非常值得关注的前兆异常。

In this paper,in combination with the analysis of tectonic activities in the Ningxia region,we use 2011—2013 gravity observation data to investigate the gravity anomaly variation before and after the 2012 Yongning M_S4.6 earthquake.We used LG-ADJ software to process the data,which has been generalized by the China Earthquake Administration.The research results show that the gravity field in the measurement area underwent good medium-term precursory variation before the 2012 Yongning M_S4.6 earthquake,after which the impending anomalies suddenly increased.The gravity field showed a sharp rise in both area and quantity.The variation tendency of the gravity point value before the earthquake showed a descent-ascent-accelerative ascent-earthquake occurrence style,which is an anomaly of widely recognized concern.