Research On Microseismic Technology In Urban Underground Space Exploration

At present,microseismic technology has been widely used in various aspects of urban underground space exploration.Compared with many traditional geophysical methods,the advantages of microseismic technology are inexpensive,easy implementation,and high precision.Microseismic technology has played an important role in the basic structure of the layer for urban construction.Common microseismic exploration data processing methods include spatial auto correlation method,frequency-wavenumber method,refraction microseismic method,etc.This article elaborated the principles and processing steps of these methods in detail,and based on the most commonly used SPAC method,realized microseismic data processing Software.Through the study and analysis of previous research results,it is concluded that the large radius combination method is more reliable in the low frequency part,and the small radius combination method is more reliable in the high frequency part,and then a method of fitting Bessel function by frequency range,and averaging dispersion curve by radius is proposed.The method expands the range of available frequencies to some extent and enhances the detection accuracy.A series of experiments confirmed the reliability of the method.In the inversion part,some common microseismic inversion methods are briefly described,focusing on the perturbation method and the non-perturbation method.The software inversion part developed in this paper adopts a good original model based on the non-perturbation method and inversions through the perturbation method.Two synthetic models are given to verify the effectiveness of the inversion method.One is a layered model for increasing shear wave velocity with increasing depth.For such models,the perturbation method can be obtained very good inversion results;the other is a layered model with lowspeed interlayers.In this model,the perturbation method can invert low-speed interlayers,but there is small error,and the other parts are still very good.After writing the microseismic data processing software,it is used in the measured data.This article mainly shows the results of some practical applications.One is the processing of the microseismic data in Guangzhou,and successfully found the unweathered granite base rock layer,which is basically the same as the histogram of the borehole;the other is the experimental data of the lawn in the school.The two-dimensional profile obtained is the same as the previous experimental results.In this paper,a complete software for processing microseismic exploration data is realized.Finally,the prospect for the development of a joint processing program for seismic exploration of artificial sources and microseismic exploration of natural sources is proposed.