The Structure Of The Crust In Fujian And Jiangxi From Teleseismic Receiver Function

The South China area,which is made up of the Yangtze block and the Huaxia block,is a popular geological research area.The area is widely distributed with intrusive granites.After undergoing multi-phase tectonic movements,the present mineral reserves are huge and the status quo is varied.Its unique geological pattern is also Shows a profound and complex tectonic evolution process.The study area is located at 114°E-117°E and 24°N-26°N in southern China.The stations are distributed in the NW-SE direction along the Gansu-Jiangxi-Longyan,Fujian province,and are distributed on the Huaxia landmass.A total of 52 mobile station waveform data from 2017 to 2018 were collected to obtain updated results of the study of the crust-mantle structure in this area,which provides basic data for the structural morphology and structural evolution characteristics of eastern South China.The research uses the receiver function H-k superposition method.The teleseismic P waves used in the method carry information about the Ps converted waves and subsequent multiple reflection waves generated by the crust and upper mantle velocity discontinuities below the receiving stations.The receiver function deducts the effect of the source effect and the response of the instrument,and contains only the information of the underground medium,from which the underground longitudinal wave velocity ratio,Poisson's ratio value,discontinuity thickness,etc.can be obtained.The final result is:(1)The crustal thickness in the study area varies from 26.6 to 34.3 km,and the average thickness is 29.5 km.The overall thickness is thin,and the trend is from thinner to thicker and then thinner and thicker from west to east.This may be because the region first experienced the continental rift activity period,and the extensional movement caused a large number of tensile fractures in the area;and then experienced the compressive tectonic activity period,which turned part of the tensile fractures into compressive fractures and produced napping Tectonics;the later extensional extension period caused each rift to open again,and finally formed the present crustal thickness distribution;(2)The wave velocity ratio in the study area is between 1.59-1.88,with an average value of 1.75.The overall value on the west side is slightly higher than that on the east side.The high wave velocity ratio is mostly distributed in the main fault zone,which may be due to the magma uplift of the deep fault Or the ejection provided a channel,and the crust and mantle material upwelled and concentrated near the fault;(3)The Poisson's ratio and crustal thickness in the study area show a negative correlation trend,which may be related to the wide range of folds and thrust nappe structures in the area.