Geophysical Data Fusion Method In Imaging And Application Based On Reflection Coefficient

Integrated geophysical investigation has become an important method to reduce multi-solution of geophysical exploration and improve the interpretation accuracy,which means the investigation was carried out with the help of various geophysical methods that have different advantages in formation physical response,investigation depth and resolution.According to the difference of physical parameters observed,geophysical methods can be divided into gravity method,magnetic method,resistivity method and reflection wave method.Each method has its advantages and disadvantages.For example,the seismic wave method characterized by greater detection depth but low accuracy because of the low detection frequency.Ground Penetrating radar(GPR)characterized by the high resolution but shallow detection depth.Also,different resistivity methods have different sensitive to the response of high and low resistivity abnormal body.Therefore,comprehensive use of geophysical exploration method could reflect more abundant geological information than the single method in terms of disaster investigation of subway,advance prediction of tunnel and interface recognition of landslide.At present,however,the expression of integrated geophysical results is still dominated by separate imaging and then comprehensive analysis.There are relatively few studies on the correlation degree and unified imaging between different types of observed data.Based on the concept of reflection coefficient,this paper attempts to convert the reflected wave data and resistivity data into reflection coefficient for fusion analysis and interpretation.Before fusion,resampling and feature reconstruction of different reflection coefficients are needed to unify the spatial and resolution.Finally,the correlation calculation and data fusion of the reconstructed reflection coefficients are carried out by means of Principal Component Analysis(PCA)transformation to obtain unified imaging of the multi-source geophysical data.Consequently,a set of more effective methods of geophysical data fusion imaging is preliminarily established.According to the above research ideas,this paper firstly processes and analyzes the theoretical response data obtained from numerical simulation.Three data fusion modes are formed by the seismic wave method,GPR,Electric Resistivity Tomography and Transient Electromagnetic:reflection wave data+reflection wave data;resistivity data+reflection wave data;resistivity data+resistivity data.For each mode,a layered and complex model are established to obtain response data,and conventional imaging analysis was conducted to find the advantages and disadvantages of single imaging analysis.Then the reflection coefficients were extracted from different theoretical response data and the imaging were compared with the conventional imaging.Finally,the PCA transformation algorithm is used to complete different reflection coefficients fusion,so as to realize the expression of geological interface based on the reflection coefficients and the fusion imaging of multi-source geophysical data.The method is also applied to the processing of measured data from multi-source geophysical exploration in a tunnel project in Jiangxi province.The reflection coefficient was extracted to image aiming at the multi-source geophysical data observed from the arch bottom and shoulder of a certain mileage range in tunnel.The features of geological structures were presented by the reflection coefficient of different geophysical methods.Then,the multi-source reflection coefficients of the two sites are fused to achieve unified imaging.The result is compared with the conventional imaging interpretation to prove the application value of this method in improving the recognition effect of geological structure interface and solving the unified imaging of multi-source geophysical data.