2023年8月6日山东平原5.5级地震前地倾斜固体潮特征及动态组合分析

Analysis of Tilt Tide Characteristics and Dynamic Combination before the Pingyuan MS5.5 Earthquake

摘要:

计算2023年8月6日山东平原5.5级地震震源附近10个台站2020年1月—2023年11月地倾斜EW和NS两分量的固体潮潮汐因子,绘制了动态组合的3种特征(扩容、剪切应变、介质各向异性)图形,并分析了其与平原地震的关系。结果表明:①天体间引潮力瞬时变化对平原地震的发生有一定的诱发作用;②M2波潮汐因子的上升与下降变化趋势大体呈四象限分布,平原地震震中位于四象限对称中心附近;③M2波潮汐因子动态组合特征量与平原地震有较好的对应关系;④一般情况下,测区介质扩容引起膨胀或剪切应变,继而潮汐因子发生阶变,最后潮汐因子各向异性出现异常。本研究对进一步分析平原地震前地球物理异常具有一定的指导意义。

Abstract:

The tidal factors of the ground tilt in the East-West(EW)and North-South(NS)components were calculated at 10 stations around the plain from January 2020 to November 2023. Time series curves for three dynamic combinations-expansion,shear strain,and media anisotropy-were generated,and their relationships with Pingyuan earthquakes were analyzed. The results show the following: (1)The occurrence of Pingyuan earthquakes is associated with instantaneous changes in tidal forces between celestial bodies. (2)The rising and falling trends of M2 wave tidal factors generally follow a four-quadrant distribution,with the epicenter of Pingyuan earthquakes located near the symmetrical center of the quadrants. (3)A strong correspondence exists between the dynamic characteristics of M2 wave tidal factors and Pingyuan earthquakes. (4)Typically,abnormal changes in expansion and shear strain-due to the expansion of the measuring area's medium-precede step changes in the tidal factor,followed by anomalies in the anisotropy of the tidal factor. This study provides valuable insights for further analyzing geophysical anomalies preceding Pingyuan earthquakes.