小震震源机制P轴取向的预报应用

采用Snoke的振幅比方法,利用江苏台网和山东台网记录到的数字化波形资料,计算了发生在江苏及其附近地区的33个地震的震源机制解,并由此计算了其相应的P轴取向。结果表明:南黄海北部凹陷地区M_L5.1地震发生前2个月内、长江口地区显著小震群发生之前2个月内,在震中所在区域的附近地区有震源P轴取向小于100°的异常地震发生;盐城附近及其近海海域在本文研究的时段内未曾出现震源P轴取向小于100°的地震,该区域也没有发生中强地震或显著小震群事件。由此说明震源P轴取向具有一定的短临前兆意义,但这种情况与大地震事件所表现出来的规律并不完全相同。茅山断裂附近地区出现的2次震源P轴取向小于100°的事件与该地区重力异常结果是一致的,说明2002年前后茅山断裂曾活动过。

The Application of the P Axis-trend of Earthquake Mechanisms to Earthquake Prediction

In this paper the source mechanisms of 33 earthquakes and the P axis-trends are obtained whichoccurred in JiangSu and its neighborhood, by using the Snoke's method of swing ratio and the digital wavedata recorded by JiangSu net and SanDong net. The result indicates that some abnormal earthquakeswhose P axis-trends are smaller than 100° occurred in about two months before ML5.1 earthquake in thenorthern Sunken region of the Yellow Sea or remarkable event occurs in the Yangtse River intake region;and no abnormal earthquakes occur whose P axis-trends are smaller than 100° and also remarkable eventsor moderate earthquakes occur in the YanCheng neighborhood and its adjacent sea area. These obviouslydemonstrate that the P axis-trend of source may be useful for the short-term and imminent prediction.which, however, is not in agreement with the phenomenon of great seismic events. The phenomenon ofthe two events with P axis-trends smaller than 100° agrees well with that of the abnormal gravity withinthe MaoSan fault area, which shows that the MaoSan fault were active around the year of 2002.