苍山4.4级地震与相公庄水准短临前兆异常

摘要本文采用逐步回归等方法处理了山东相公庄水准 EW、SN 向1989年1月1日至1990年9月30日的五日均值观测资料。回归分析结果表明:苍山4.4(M_L)级地震前相公庄水准 EW、SN 向均有10天左右的短临前兆异常,异常最大幅值分别为0.84mm和0.42mm,地震发生在异常达最大值的前一天,回归剩余标准差分别为±0.17mm和±0.12mm。据动态灰箱法处理的结果说明:短临异常在月均值上也有一定显示,只是幅度小些。作者认为:距震中50km左右的定点形变台,在一定条件下有可能监测到4级以上地震的短临前兆异常。

ON THE CANGSHAN EARTHQUAKE OF 4.4MAGNITUDE AND THE SHORT-TERM PREMONITORY ANOMALY OF XIANGGONGZHUANG LEVELLING

A set of seismic observations averaged over 5 days collected from Jan. 1-st, 1989 to Sept. 30-th, 1990 in Xianggongzhuang levelling EW and SN oriented in Shandong Prow- ince has been processed by using a step by step regression method. The result shows that be- fore the Cangshan earthquake, there have been a short-term premonitory anomaly with maximum magnitude up to 0.84 and 0.42mm and the earthquake occurred one day before the anomaly reached its maximum. The residual standard deviations are ±0.17 and ±0.12 mm after regression process. The result from the Dynamic Grey-Box method shows that such a short-term anomaly can also be seen on monthly averaged observations except for the smaller magnitude. It's believed that the deformation observation stations around 50km away from the epicenter may be available in monitoring the short-term premonitory anom- aly related to an earthquake with intensity greater than 4.0 magnitude under certain circum- stances.