Research On The S-wave Velocity In The Crust And Geodynamical Mechanisms Beneath Sichuan

In this paper,162 teleseismic seismogram recorded in the Sichuan areas and its adjacent areas,ranging from 25 °N-34° N and longitude range from 98 °E-108 °E to a total of 49 stations were studied.By calculating the P-wave data of each station,the P-wave receiving function with Gaussian parameters of 1.0 and 2.5 is obtained,and then the receiver function is selected to collect the receiving function of each station.Then,the S-wave velocity structure of the Gaussian parameter 1.0 is obtained by inversion of the S-wave velocity structure by selecting a simple initial model,and then the Bootstrap method is re-sampled to obtain Gaussian Parameter 1.0 The speed structure of each station.Then the second inversion is carried out with the reference model of the receiver function with the velocity structure of Gauss parameter 2.5,and the final velocity structure under the station is obtained by resampling the Bootstrap method.According to these velocity structures,the depth of the Moho surface,the distribution position of the low speed station,the contour map of the different depth and the section of the velocity structure are calculated.Finally,the analysis of these maps is carried out,and it is hoped that the activities of the underground material structure and geological structure,the crustal velocity structure and the regional deformation mechanism and the dynamic mechanism can be further understood.Main results:1.The reliability of the inversion method with two reference models and the feasibility of the Bootstrap resampling method are proved by the numerical simulation.2.In the Songpan area,the depth of the low velocity zone is relatively concentrated at 20-35km,the low velocity value is not too low,and the mass of the Sichuan-Yunnan diamond block is lower than that of the Sichuan Basin.The crust has a large area of low-speed areas extending from a depth of 25 km to a depth of 45 km.3.There are obvious inhomogeneities in the horizontal depth of the Moho field in the study area.In particular,there are great differences in the burial depths of the Moho surface on both sides of the Longmen Mountains.From the Mohao contour map,The line is densely packed on the west side of Longmen,with a depth of about 40-43km in the east and about 52-60km in the west.4.According to the results of this paper,this paper supports the hypothesis of lower crust material flow.The eastern crust of the Qinghai-Tibet Plateau is extruded in the east,which is limited by the blockage of the hard Sichuan Basin and the structural constraints of the East Himalayan tectonic facies.Some of them are dipped into the Sichuan-Yunnan rhombic block by the Batang block,Yunnan area,part of the material breakthrough Lijiang-Xiaojin River Duanli flow to the southeast direction.