地电场日变幅各向异性度异常提取方法初步研究

Preliminary Study on the Extraction of the Anisotropy Anomaly of Daily Amplitude Variations in a Geoelectric Field

摘要:

首先建立地电场日变幅各向异性度(S值)方法：对不同测向的地电场日变幅换算成各向异性系数，进而提取异常信号的方法。通过对不同台站的映震结果的对比分析表明：(1)该方法能够较好地识别地震前兆信息异常，对于5级左右地震，在震前4个月之内，震中距200 km范围内各台能够记录到地震的短期异常，异常出现的早晚与各台震中距的远近有关；对于4级地震，震中距越近异常越明显；(2)在正常情况下，S值曲线一般在均值的2倍均方差以内波动；当出现异常时，异常判据为S值2日以上超过各台均值的2倍均方差、曲线形态发生畸变；(3)各台映震结果存在较大的差异性，这可能与地下介质电性结构、发震构造与各台构造关联性存在一定关系。

Abstract:

In this study, the anisotropy degree (S-value) method of daily amplitude variations in a geoelectric field was proposed. Seismic reflection results obtained using the proposed method at different stations were compared and analyzed. Results showed that (1) the method can recognize anomaly precursors. The short-term anomalies of M=5.0 earthquakes with an epicenter distance of about 200 km can be recorded at each station within 4 months before an earthquake. The occurrence time of anomalies at different stations is related to epicenter distance. (2) Under normal circumstances, the S-value curve generally fluctuates within two times the mean square deviation of the mean. When the S-value in 2 days exceeds the value of two times the mean square deviation of the mean and the curved form is distorted, an anomaly appears. (3) Seismic reflection results from each station remarkably differ. Their difference may be related to the electrical structure of an underground medium, a seismological structure, and the related structure of each station.