大地电场观测地震前兆异常提取技术研究

Research on the technique of extracting seismic precursory anomaly from telluric electric field observation

首都圈地区布设的11个地电场观测台于2001年9月已正式投入观测,现已积累了近7年的资料.使用大地电场观测系统中同一测向的长、短极距测值的比值方法,对其中的10个台和邻区2个台的资料进行了处理,发现该方法能够较好地排除来自大地电场及自然电场远场的变化信息,突出了可识别的地震前兆异常信息.研究结果表明,2006年7月4日河北文安MS5.1地震前,多数台站的地电场观测资料出现比值异常变化,从而证明了这次地震前地电场观测存在着短临异常前兆变化信息,只是由于这些信息混杂于正常大地电场变化的背景中,使用常规的分析方法无法识别和提取.研究结果还表明,地电场观测的台址条件和台址到震中区的距离与震前地电场比值异常出现的时间和幅度有关.

Eleven stations for telluric electric field observation have been running normally in the area around the capital of China since September, 2001. Up to now the data have been accumulated for nearly seven years. In this paper, we processed the data from 10 stations in the capital region and 2 other stations in its neighbor area by finding the ratio of long to short electrode spacing observation in the same measuring direction. The result indicates that this method can effectively exclude disturbing information from telluric electric field and from remote spontaneous electricity field,and then identify seismic precursory anomaly. Many stations observed short-term anomalous variations before the M5.1 Wen＇an earthquake of 4 July 2006, but researchers could not identify and distill them because they were merged into background variation. The study result also indicates that the appearing time and variation amplitude of the precursory anomaly have bearing to the station condition and station-to-epicenter distance.