Research On Restraining The Known Source Interference In Geoelectric Field Observation

Geoelectric field observation has very important practical sense in detecting earth interior electrical structures and forecasting earthquake. The problems of electromagnetic environment interference are more and more serious in China. Geoelectric field .signal output by earthquake electromagnetism station always have varieties of noise jamming. Restraining these noises jamming becomes absolutely necessarily in geoelectric field observation. This paper is established in software filter method, based on minute sampling and second sampling geoelectric field data, research on restraining and filtering some regular interferences, implement real-time identification and extraction for geoelectric field signal from strong electromagnetic environment interference.This paper first introduced principles of geoelectric field observation and generation mechanism and characteristic of resistivity equipment artificial electricity interference, and metros leakage interference were especially investigated. The time domain and frequency domain character of geoelectric field signals and some interference signals were detailed analysed. Research shows that the investigated interference signals and geoelectric field signal are aliasing in frequency domain. These interferences can't be filtered by conventional time domain or frequency domain filtering methods.Discusses the wavelet transformation elementary theory, and introduces the dyadic wavelet transform, multi-resolution analysis, Mallat algorithm and the theory of wavelet domain threshold filtering. Wavelet domain threshold filtering method is applied to restraining resistivity equipment artificial electricity interference and metros leakage interference. Based on characteristic of geoelectric field signals and the investigated interference signals,decompose layer and wavelet function are confirmed. In the wavelet domain threshold filtering, the selected threshold value direct impact on the filtering effect, and the traditional wavelet threshold selection rules do not apply to geoelectric field signals. By numerical simulation experiments, for different signal interference identified a different threshold selection rules, the interferences in geoelectric field signals were restrained successful. The basic principles of classical LMS self-adapting filtering algorithm and wavelet domain LMS algorithm were expounded and applied to restraining resistivity equipment artificial electricity interference. Then made some numerical simulation experiments, and he best adaptive filter parameters are determined. Filtering results showes that resistivity equipment artificial electricity interference is removed cleanly and effectively. It is also testified that wavelet domain LMS algorithm is more effective than classical LMS algorithm.Paper finally realize eliminating noise with the actual measurement geoelectric field observation signal, including resistivity equipment artificial electricity interference, metros leakage interference, pulse-like interference of Minshan station. Paper achieved the expected goals in practical disposal. And its main application and the existing problems were discussed in this paper can be extended to analysis and processing of other non-frequency interference signals in geoelectric field observations, as well as conventional analysis and information extraction of geoelectric field observations.