Study On Characteristics Of Rugged Terrain Effect Of Ground-Airborne Transient Electromagnetic

Ground-airborne transient electromagnetic method has been paid more and more attention in field survey because of its advantages in detection efficiency,cost and safety.Especially in the detection of undulating areas,ground-airborne transient electromagnetic method has become one of the preferred methods.However,most of the current explanations of groundairborne transient electromagnetic data are based on flat terrain conditions.Neglecting the terrain effect caused by the undulating terrain and directly processing the data will reduce the accuracy of data interpretation.Therefore,further understanding of the undulating terrain effect plays an important role in the wide application of ground-airborne transient electromagnetic detection methods.Based on this problem,this paper studies the terrain effects of groundairborne transient electromagnetic fluctuations.For the forward modeling of the ground-airborne transient electromagnetic model,it is mostly calculated by first calculating the attenuation voltage of the magnetic field and then integrating to obtain the magnetic field value.The shortcoming of this method is that it will inevitably produce errors in the process of calculating the integral,thus reducing the accuracy of the field value results.Based on the predecessors,this paper modifies the finite element threedimensional forward program,so that the magnetic field value of the ground-airborne transient electromagnetic method can be directly calculated by the algorithm program,which avoids the error that occurred in the integral calculation process and improves.The reliability of forward data.In this paper,several typical undulating terrain models(slopes,valleys,ridges,combined peaks and valleys)are numerically simulated under pure terrain conditions and under anomalous conditions.The ground motion electromagnetic field values under two conditions are obtained.The magnetic induction multi-track curve and the apparent resistivity profile are drawn,and the analysis results show the influence characteristics of the undulating terrain effect under different terrains.Then the forward modeling of the undulating model under different parameters is carried out,and the variation law of the undulating terrain effect under different parameters(flight mode,receiving height,offset,terrain electrical,etc.)is discussed.Based on the forward modeling and results analysis of the undulating terrain model,this paper summarizes the influence characteristics of ground-airborne transient electromagnetic terrain effects under different undulating terrain conditions,and provides reference for terrain correction and further data interpretation of ground-airborne transient electromagnetic data.