Research Ondensity Interface Inversion Based On The Laterallyvariable Density Modelin Frequency Domain And Its Application

Inversion of density interface is an important method to deduce the structure of the basement and Moho surface.Conventional density interface inversion method is mostly based on constant or vertically variable density model.In the regional tectonic studies of large area,different blocks or tectonic units always have differences in crustal composition and structure,leading to a density lateral difference of crust,which means the conventional interface inversion method based on constant or vertically variable density model is not applicable.In this paper,a density interface inversion method based on the laterally variable density model in frequency domain is developed.The influence of relevant inversion parameters is evaluatedand this technique is used to obtain the depth distribution of the Moho surface in the eastern Ordos Basin.This method is of theoretical and practical significance for improving the inversion result of regional density interface,promoting regional structural interpretation and so on.The main achievements and understanding of this paper are as follows:(1)The inversion formula based on laterally variable density model in frequency domain is derived theoretically.The construction method of laterally variable density model is given and the flow of inversion algorithm is built.At the same time,a low pass filter is introduced to improve the inversion stability.(2)The validity of this method is verified by synthetic model data test.The evaluation of parameters show that the datum plane and filter factor have little influence on the interface inversion and can be adjusted by experiments,while the laterally variable density model have great influence on it.Therefore,the key to the application of this method is to build a reasonable and effective laterally variable density model.(3)The depth distribution of Moho in the eastern part of Ordos Basin is obtained by using this method.The results show that the inversion results of the laterally variable density model constructed by the seismicvelocity-density conversion formula are close to the results of previous seismic detection.The Moho surface in the study area is deep in the west and shallow in the east(30-50 km),the Moho depth is about 40 km in the Ordos Basin,42-45 km in the northern and Yinshan regions and 34-42 km in the east margin.A Moho cascade with NNE trendin Taihang Mountain is presented.The crust is thicker in the west and thinner in the east.