Characteristics of geophysical response and fine identification of multi-stage strike-slip fault in Tabei area
Through the comprehensive analysis of field geological outcrop inspection,UAV scanning,ground penetrating ra-dar(GPR),core observation,and imaging logging data,a geological model of fault-controlled karst cavern in Tabei area was established.According to the characteristics of different strata in Tabei area,the relationship between multi-stage strike-slip faults and strata combination in different periods have been studied.According to the characteristics of strike-slip faults under different stratigraphic lithofacies backgrounds,the corresponding geophysical response characteristics are analyzed,which provides a basis for the identification of strike-slip faults with small fault throw and small distance of displacement.The re-sults show that in the Middle to Late Caledonian,regional strike-slip faults formed under extrusive stress,developing X-shaped conjugate faults and single shear faults,with NE and NNE-oriented strike-slip faults being left-lateral slip and NNW-oriented faults being right-lateral slip.Due to the differential distribution of extrusive stresses,the linear compressional-tor-sional uplift and translational misfracture of the slip surface of the Cambrian gypsum-salt rocks along the direction of the trunk fracture,combined with the strong seismic reflection characteristics of the plutonic salt formation,the PDZ of slip fault is highly identifiable.The strike of the Middle and Upper Ordovician strike-slip fractures is consistent with palaeotopographic trends.A large number of remnant hills,underground karst conduits and ancient water systems have formed in the study area as a result of the long period of surface karst exposure in the north,destroying the shallow fault features.In contrast,the southern slope area is short exposed,karst reservoirs are mainly developed along the slip fault,and there are large differences in wave impedance between fault-controlled karst reservoirs and carbonate bedrock,enhancing the identifiable characteristics of the fault.Single-shear strike-slip faults develop in the NNW direction in the Hercynian period and the NNE direction in the Himalayan period,mainly along the inherited development of the mid-Caledonian fault,and the unconformity of the clas-tic stratigraphy forms a distinctive break-spacing feature,which has an echelon in the spatial distribution,with negative flow-er structure visible in the section.
ground penetrating radar(GPR)slip faultskarst-fracture cavemulti-attribute analysisTabei area
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