【摘要】 强震前地磁垂直分量日变化异常主要表现在幅度与相位上的变化.利用中国地磁台网多年观测资料,研究了2008年5月12日四川汶川8.0级地震前,地磁垂直分量日变极小值出现的时间(低点时间)在空间分布上的异常特征,即低点位移现象;并用此方法预测了汶川8.0级地震6级余震平静2个月后的一组6级强余震.这种少见的异常现象与强震发生有较好的相关性.发震日期为异常出现后的第27天或第41天的前后4天,强震发生地区在低点位移突变分界线附近.此外,还研究了汶川8.0级地震临震前,震中周围出现的地磁日变幅异常现象.更多还原

【Abstract】 Before strong earthquakes the diurnal variation of geomagnetic vertical component menifests itself mainly in phase and amplitude changes. Based on the data recorded by geomagnetic observatories in China for many years, anomalous features of the appearance time of the minima in diurnal variation (i.e, low point time) of the geomagnetic vertical components, and the variation of their spatial distribution (i.e, phenomena of low point displacement), before the 2008 Wenchuan MS8.0 earthquake have been studied. The strong aftershocks after two months quiescence of M6 aftershocks after the MS8.0 event were predicted based on these studies. There are good correlations between these rare geomagnetic anomalies and the occurrences of earthquakes. It has been found that most earthquakes occurred near the boundary line of sudden changes of the low point time and within four days before or after the 27th or 41st day since the appearance of the anomaly in general. In addition, the imminent anomalies in diurnal variation amplitudes near epicentral areas before the Wenchuan MS8.0 earthquake have been studied.更多还原