Application Of Controlled Source Audio Magnetotelluric Method In Complex Terrain

With the increasing application of CSAMT in practical exploration,many problems in exploration have gradually emerged,such as topographic change,shadow effect,static effect and so on.Among them,topographic change has a widespread impact on the use of electromagnetic method,which leads to poor accuracy of exploration results,and will bring greater errors to data processing results,affecting the detection accuracy of CSAMT method.In this paper,based on the height difference fluctuation of the topography of a coal mining area,the geological models of valleys,ridges and slopes are established by using the software SCS2 D.The apparent resistivity response of CSAMT method under different topography(valleys,ridges and slopes)is studied by setting up a low resistivity geological body with the same size at buried depths of 300-350 m,500-600 m and 800-900 m,respectively.The relationship between sign and burial depth of anomalous body.The results show that the response characteristics of topographic changes(valleys,ridges and slopes)to CSAMT detection results have a greater impact on the low resistivity body with shallow burial depth and a smaller impact on the low resistivity anomaly body with larger burial depth.On the basis of the above work,the apparent resistivity response characteristics of CSAMT method for low resistivity anomalous bodies with the same burial depth(m),resistivity and wall rock resistivity but only changing topographic factors(valleys,ridges and slopes)are studied.By comparing and analyzing the response characteristics of the three terrain models,the results show that the valley terrain has the greatest impact,the ridge terrain has the second impact,and the slope terrain has the least impact.Secondly,the apparent resistivity response characteristics of CSAMT method are studied when the same burial depth(m),the same resistivity and the same terrain of low resistivity anomalous body only change the factors of resistivityof surrounding rock.By comparing and analyzing the response characteristics of three topographic models,the results show that the small influence of resistivityof surrounding rocks is greater than that of resistivity.Taking slope topography as an example,CSAMT is studied when the low resistivity anomaly body has the same burial depth(m),the same resistivityand the resistivity of surrounding rocks but only changes the inclination angle.Apparent resistivity response characteristics of the method.The results show that the bigger the inclination,the smaller the impact.Finally,the CSAMT apparent resistivity forward modeling results caused by topographic changes are applied to the exploration and application of underground water accumulation anomaly area in a coal mine,and the scope of water accumulation anomaly area is accurately divided.The location of the anomalous zones is basically consistent with the location of the anomalous zones,which proves the effectiveness of the forward modeling method.