包头西6.4级地震前显著中等地震活动增强和丛集异常

Obvious intensifying and swarming anomaly of moderate seismic activity before west Baotou earthquake with M=6.4

1996年包头西6.4级地震前,在震中西部临河盆地出现了显著的中等地震活动增强和丛集异常,而且中等地震活动在时间上也表现出了集中的特征。其中5次中等地震强烈有感,引起了地震学者高度的重视,这是一次显著的地震活动中期异常。但是,主震是在距离异常区200km以外的地方发生,造成了震前地点预测误差较大的问题。文中详细描述了这次中等地震活动异常的情况,并且通过震区地震地质构造条件分析,探讨了主震发生在距离异常区较远的原因,这对今后地震预测有一定的指导意义。

Before West Baotou M_S6.4 earthquake occurred on May 3rd 1996, in the western part of epicenter in Linhe basin, the obvious intensifying and swarming anomaly of moderate earthquake activity appeared, besides, the time sequence of moderate earthquakes is also characterized by concentration. The five ones among these moderate earthquakes are strongly felt so we paid more attention to these events. It is a remarkable medium term anomaly of seismicity. Unfortunately, the main shock was not near the anomalous area; it occurred in the area farther away from the anomaly point 200 km or so. This phenomenon resulted in our wrong prediction of earthquake place. In the paper, the author described the details of moderate earthquake activity. In addition to this, by analyzing the tectonics of Linhe basin, the author also discussed the reason why main shock occurred farther away from the anomalous place. Undoubtedly, it is of significance in our earthquake prediction in the future.