开展小极距井下地电阻率观测的可行性分析

目前,我国用于地震监测的地电阻率观测面临着两个难题:①测区范围较大导致台网稀疏且分布不均匀;②易受环境干扰。本文结合台站实际的地下电性结构,采用地电阻率解析表达式和有限元数值分析方法,对开展小极距井下地电阻率观测的可行性进行了讨论。结果表明:小极距井下观测方式能有效抑制地表电性异常体类干扰和年变化的影响,也能记录到地表大极距观测和井下大极距观测所能记录到的震前异常变化。小极距井下观测能大幅减小布极区范围,有助于地电阻率的足密度组网成场观测,可为解决目前地电阻率观测面临的难题提供一种可选方案。

Feasibility Analysis on Short-electrode Spacing Well Apparent Resistivity Observation

Currently, apparent resistivity observation used in the earthquake prediction of China has been facing two serious difficulties. One is the sparsely and unevenly distributed networks, and the other is the susceptibility to environmental disturbances. One of the possible causes to the difficulties is the large-electrode spacing presently used at stations. In this paper, we will take an analysis on the feasibility of short-electrode spacing well measurement by the use of apparent resistivity analytical expression and finite element numerical method. Results display that the disturbance from surface electric anomalous bodies and annual variation effects can be well inhibited by the use of short-electrode spacing well measurement. And the new type of measurement can record anomalies associated with earthquake as effective as surface large spacing measurement and large spacing well measurement. Short-electrode spacing well measurement greatly reduce the covering areas needed, and can be helpful to field network observation. Therefore, it provides an alternative scheme to settle the difficulties current observations face.