地磁短周期变化预报方法的研究

RESEARCH ON EARTHQUAKE PREDICTION METHOD WITH GEOMAGNETIC SHORT PERIOD VARIATIONS

研究地磁短周期在地震前是否存在异常变化,为地震预报探索新途径。针对华北地区近十多年先后发生唐山7.8级、隆尧5.8级、任县5.0级及菏泽5.9级地震,量取昌黎、长春、北京、红山、菏泽及郑州等六个台自1971年至1988年三分量磁照图上的短周期变化幅度△Z、△H和△D,计算△Z/△H和转换函数a、b值随时间变化,其结果:唐山7.8级地震前,距震中72公里的昌黎台存在4年负异常,最大下降幅度为35％,隆尧5.8级地震前,距震中24公里的红山台,存在3年负异常,下降幅度为29％;任县5.0级地震前,距震中20公里的红山台,存在2年负异常,下降幅度为14％;菏泽5.9级地震前,距震中20公里的菏泽台也有明显异常(该台震前一年多才有资料)。而距震中较远的北京,郑州等台的异常不明显。研究表明,地震的震级与震中距离、异常幅度、异常持续时间等要素存在一定的相关性;转换函数a和△Z/△H的变化基本上等效,但从地震预报方法的普及性和实用性来看,直接用△Z/△H来探测震磁前兆信息最简便易行。

The parpose is to study wether there exist anomalous variations in geomagnetic short-period changes before earthquakes so as to search a new way for earthquake prediction. In light of Tangshan Mi 7.8, Longyao MS 5.8, Renxian Ms 5.0 and Heze MS 5.9 earthquakes occurred successively in North China in recent 10 years or earlier we have measured the short-period variation amplitude AZ, AH and AD on the three-component magnetic chaets at Changli, Changchun, Beijing, Hongshan, Heze and Zhongzhou stations from 1971 to 1988, and calculated variations of △Z/△H and transfer function a and b values with time. Results show that before the Tangshan Ms 7.8 earthquake, there had existed 4-year negative anomaly at Changli station 72 km to the epicenter, the maximum decrease amplitude was 35%; before Longyao MS 5.8 earthquake, there existed 3-year negative anomaly at Hongshan station, 24km to the epicenter, the decrease amplitu tude was 29%; before Renxian MS 5.0 earthquake, there existed 2-year negative anomaly at Hongshan station 20 km to the epicenter, the decrease amplitude was 14%; before Heze MS 5.9 earthquake, there were obvious anomalies at Heze station 20 km to the epicenter (as the Heze station had only one year records before the event). The anomalies at Beijing and Zhengzhou stations far from the epicenters were not clear. Studies show that there exist a certain correlatabilities among earthquake magnitude, picentral distance, abnomal amplitude and time duration of anomalies. The variations of the transfer function a and △Z/△H are basically equivalent, but from the view point of the popularity and utility of the earthquake-prediction method, it is simple and easy to adopt △Z/△H directly to explore seismo-magnetic precursory information.