Research On Key Technology Of Geospectral Exchange Observation System

In the past ten or twenty years, more and more geo-resistivity observation stations are being faced with increasingly electromagnetic interference, such as subway and rail traffic system in urban area, which seriously affects the quality of observation data. The AC geo-resistivity observation method has been found effective to solve this problem and can be used for earthquake monitoring and prediction.The AC geo-resistivity observation method is based on Electrical exploration methods and DC geo-resistivity observation method. When the AC signal frequency is between 10-3Hz-103Hz, it can be approximately considered the AC electric field follows Ohm’s law, and the AC electric field can be regarded as quasi-static electric field.First of all, three different signal detection methods, the digital filter method, the correlation detection method and the spectrum analysis methods, are used in the simulation. The analysis results are obtained by simulating an actual work process of AC geo-resistivity observation method and comparing the relative error and relative standard deviation in different signal-noise ratio (SNR), sampling rate (Fs) or sampling time. Meanwhile, considering the system hardware design and realization, the spectrum analysis method has been chosen as a suitable signal detection method to detect signal amplitude.In second instance, the signal characteristics of subway interference are analyzed and summarized by testing site responses of Beijing Xiji seismic station, Tianjin Qingguang seismic station, Liaoning Xinchengzi seismic station and Jiangsu Jiangning seismic station. The results are shown that the subway interference signals has a frequence of 120s-180s and the effect on SNR of sites is about 20dB-30dB.In third instance, based on the characteristics of subway signals, using the spectrum analysis method, the influence of real subway signals on geo-resistivity observation is simulated to verify the feasibility of AC geo-resistivity observation method.Finally, on the basis of all the above study, the main technical criteria for designing and developing the AC geo-resistivity observation system is summarized, which might provide theory reference and technical basis for AC geo-resistivity observation system.