利用地电场线性极化特性提取地震前兆异常的方法研究

Method of Extracting Earthquake Precursor Anomalies Based onthe Linear Polarization Characteristics of a Geoelectric Field

摘要:

处理平凉台2008-2017年的地电场观测资料，首先对地电场线性极化和非极化异常进行分析，提出利用地电场线性极化特性提取地震前兆异常的方法。其次，采用相关数据处理和计算方法对周期性质、极化系数、极化方向、垂直极化方向上的投影等进行讨论，结果表明平凉台地电场线性极化正常背景特征为：极化方向变化范围N（66.7±6）°E，极化系数在0.7~1之间，垂直极化方向上的投影值波动范围（-0.53~2.61）mV/km。最后，统计分析平凉台周边中强地震与地电场非线性极化异常的关系，认为平凉台地电场对中强地震有较好的映震能力，地电场非极化异常可以作为判断地震前兆异常的一个重要指标，其异常表现为：从震前非极化到震后恢复极化的一个过程，持续时间一般在4~15天，多出现在震前5天到1个月不等。

Abstract:

In this study, the observation data of a geoelectric field at Pingliang Station were collected from 2008 to 2017. The linear polarization and nonpolarization anomalies of the geoelectric field were analyzed, and a method for extracting seismic precursor anomalies was proposed on the basis of the linear polarization characteristics of the geoelectric field. Periodic properties, polarization coefficient, polarization direction, and projection in a vertical polarization direction were discussed with a relative data processing method. The following normal background characteristics of the linear polarization of the geoelectric field at Pingliang Station were obtained. The polarization direction varies within N(66.7±6)° E, and the polarization coefficient is between 0.7 and 1. The fluctuation range of the projection value in the vertical polarization direction varies from -0.53 mV/km to 2.61 mV/km. The relationship between moderate and strong earthquakes around Pingliang Station and the nonpolarization anomaly of the geoelectric field was analyzed statistically. Results showed that the geoelectric field at this station can reflect earthquakes. The nonpolarization anomaly of the geoelectric field can be used as an important indicator of earthquake precursor anomalies; that is, the duration from nonpolarization before the earthquake to polarization recovery after the earthquake generally ranges from 4 days to 15 days and occurs mostly within 5 days to 1 month before the earthquake.