Crustal structure characteristics beneath the Shandong-Jiangsu-Anhui segment of the Tan-Lu fault zone and its adjacent regions using receiver functions

Using 763 teleseismic waveform data recorded in 5 years by 261 broadband seismic stations in the Shandong-Jiangsu-Anhui segment of the Tan-Lu fault zone and adjacent areas, 10846 teleseismic P-wave receiver functions were calculated and filtered. The P-wave receiver function H-kappa method was used to obtain the crustal thickness and the average Poisson's ratio in the crust, and the CCP (Common Conversion Point) method was used to further reveal the undulation pattern of the Moho interface below the station. The comparison shows that the crustal thickness distribution characteristics obtained by the two different methods have good consistency. The research found that: (1) The Moho interface burial depth in the study area varies in the range of 27 similar to 40 km, with an average depth of similar to 34 km, and generally shows the characteristics of thinness in the east and thickness in the west with the Tan-Lu fault zone as the boundary. The thickness of the crust varies significantly between or within blocks, indicating that different geological units have undergone different tectonic evolutionary processes. (2) The Poisson's ratio of the crust in the study area varies between 0.15 and 0.32, and the average Poisson's ratio is 0.24, which is slightly lower than the average Poisson's ratio of the global continental crust and the Chinese continental crust; however, the larger floating range of Poisson's ratio means that the crustal material in the study area has strong lateral heterogeneity and complex material composition. There is an anomalous zone of high Poisson's ratio in the NNE-SSW direction along the Tan-Lu fault zone, which is presumed to be caused by the upwelling of ferromagnesian basal rocks to the crust along the Tan-Lu fault zone, or the bottom intrusion of high temperature and high pressure mantle-derived thermal material into the lower crust. (3) There is an inverse correlation between the crustal thickness and the average Poisson's ratio within the crust in the study area; the crustal thickness and the surface geomorphic features show a mirror relationship, i.e., the Moho interface is buried deeper in the orogenic uplift area and shallower in the plain basin area. The Moho burial depth contour distribution map and the Bouguer gravity anomaly feature in the study area correspond well. (4) The CCP stacking method for the Moho interface is in good agreement with the crustal thickness results obtained by the H-kappa stacking method, and the CCP section shows that the Tan-Lu Fracture Zone is not only a divisional fracture between the Yangzi fault block area and the North China block, but also a deep and large ultracrustal fracture zone cutting through the Moho surface and reaching the upper mantle with a misalignment of 4 similar to 7 km. (5) Some of the stations in the study area have intracrustal interfaces below them, and their burial depths can still be obtained by the H-kappa method after changing the intracrustal velocity.