Study On Deep Overburden Area Comprehensive Geophysical Mapping Technique In Hetao Basin

In the Hetao Basin,there is a thick layer of sedimentary covering,mineral resources and rich resources,which have great economic potential,but the structure is complex.China geological survey project approval within the basin to develop geological mapping work,as a result,the application of comprehensive geophysical method of basin coverage detection,provide geological mapping work with sedimentary coverage area of underground concealed geological information,in order to understand the tectonic activity,sedimentary layered geological problems,to serve the local national economy.According to the objectives of the project,in the study area has deployed the high accuracy gravity and magnetic method,CSAMT high-density resistivity and surface wave seismic profile measurement,This paper uses the data of heavy,magnetic,electrical and seismic profiles to carry out the research of underground structure and construction of the basin,combined with planar magnetic data and predecessor' s achievements of regional geological geophysical anomalies in the processing and comprehensive analysis and explanation,and give a semi quantitative three-dimensional structure,obtained the coverage area of subsurface structure model.Magnetic profile data is 2.5 D joint inversion,with the RGIS2010 software by planar magnetic and gravity data processing and profile data inversion results confirmed the research area of five zones,including four buried fault,the other for the color,the piedmont fault,has exposed on the surface.Profile data also shows that the study area south of the basement depth of 2.5 ~ 4.1 km,north central basal maximum depth of 6 km,North Seerteng before the fault zone began to rapidly rise to 0 ~ 1 km.The detection of electrical method is mainly arranged in the northern part of the northern part of the industrial area and the base of the northern bank of the Yellow River.The ultra-high density electrical method can directly reverse the true resistivity of the underground medium,and its inversion results show that the underground resistivity is low and the water content is high.The electrical stratification is obvious,which indicates the approximate level of basin formation.Single point of CSAMT data inversion resistivity distribution display,according to the observation results of inversion of resistivity distribution point below the resistivity distribution showed good transversely isotropic,low resistivity,stable sedimentary environment.Surface wave inversion results show that the basin in the shallow surface velocity layering,0 to 3 m below the surface for low-speed covered by loess in the loose layer,4 to 6 m for high speed slightly more dense loess overburden velocity layering,6 to 8 m is lacustrine facies loose gravel layer at low speed,9 m the following structure for high speed.According to the result of magnetic inversion,CSAMT inversion results and a depth of field analytical signal inversion results drawing the coverage area of 3 d geological structure model,indicating the basal,underground concealed fault non-uniform density and the spatial distribution of the magnetic body half quantitative characteristics.Based on the natural seismic data collected,the project was projected in the study area,with a significant natural earthquake gathering around four hidden faults.The data collection time was 1971-2016,and there were few natural earthquakes in the vicinity of the seelten mountains,indicating that the area has been stable since 1971.In view of the automatic inversion of potential field,at home and abroad in recent years,there appeared the analytic signal,edge recognition,euler inversion,such as the use of analytical signal rapid inversion objective geologic body buried depth,edge detection can effectively identify with physical differences of geologic body edge position,is one of the widely used numerical method,and using time of the original exception mixed derivative geological boundary location.Selected on the basis of modeling,the total level gradient model to deal with the actual data,the frequency domain is sometimes affected by high frequency interference,upward continuation as a low pass filter method is simple,the effect is good.Due to the actual magnetic anomaly is often affected by magnetic anomaly component and the direction of magnetization,identify the location of the will and the actual position deviation is bigger,so need to the magnetic anomaly processing.Finally,five points are used to filter out the conditional extremum,so as to sharpen the boundary.In this paper,we integrate the data processing algorithm,edge recognition and automatic inversion of frequency domain,integrated by using C + + programming language developed MDPv1.0 potential field processing and graphics software,the main features include magnetic anomaly pole and potential field continuation,modeling,edge recognition,rapid depth inversion,and geological mapping display,etc.,it provides an auxiliary tool for subsequent data processing and visualization of results.