2008年河南封丘4级震群前后重力场时空演化特征

The Temporal-spatial Variation Features of Gravity Field before and after the Fengqiu Earthquake Swarm in 2008 in Henan Province

河南封丘4级震群尤其是ML4.8地震前后重力场的变化和动态演化特征的研究表明:震前冀鲁豫测区的重力场出现上升→下降→上升变化可能是较明显的中短期前兆异常反映;封丘地震发生在重力加速变化过程中。重力场动态图像较清晰地反映了孕震区准均匀态→非均匀态→发震的演化过程。震后该区的重力异常没有恢复。还介绍了根据重力异常对封丘地震预测的过程。

The variation features of gravity field and seismicity before and after the Fengqiu earthquake swarm are discussed based on the data of gravity monitoring network in border region of Hebei - Henan - Shandong provinces. The results show that the ascent→descent→ascent variations of the gravity field before the earthquake are the obvious reflection of medium-short-term anomalies in the gravity field, and the earthquake occurred during changing stage of acceleration. The dynamic images reflect clearly the evolu- tionary process of the gravity field in the seismogenic zone, i.e. quasi-homogeneous state→inhomoge-neous state→earthquake occurrence. After the earthquakes, the gravity anomalies in this region did not recover. The prediction of Fengqiu earthquake according to the gravity anomalies is presented in the paper also.