Three-dimensional crustal velocity structure beneath the southern segment of the Tan-Lu fault revealed by joint inversion from multi-source data

The southern segment of the Tan-Lu fault zone is located in the intersection of different blocks, high-resolution crustal velocity structure is helpful to understand the structural characteristics and formation mechanisms in this region. Based on the body wave signals and high-frequency surface wave signals from the Anhui Airgun Experiment in 2015, the body wave signals of regional earthquakes from 2008 to 2018, and the surface wave dispersion of ambient noise, we jointly inverted the surface wave dispersion data and body wave travel times from different sources and different periods to obtain the high-precision crustal V-P, and V-S structure beneath the southern segment of the Tan-Lu fault zone. The results show that: (1) By adding surface wave data for joint inversion, the resolution capability of the obtained P-wave and S-wave velocity models in the middle and lower crust is significantly improved compared with inversion results using single body wave data. (2) Large velocity contrasts are observed across the Tan-Lu fault zone, which is the main factor controlling local geophysical/geological anomalies. Earthquakes are primarily concentrated near faults and are mostly located in areas with high- and low-V-P and V-S anomalies. (3) There are high velocity bodies beneath the Qinling-Dabie Orogenic Belt (QDOB), corresponding to the ultra-high-pressure metamorphic rocks, which are formed by the uplifting and exhumation of the deep subducted continent after undergoing ultra-high-pressure metamorphism. (4) The ore deposits beneath the Middle-Lower Yangtze River Metallogenic Belt (MLYRMB) present high P-wave and S-wave values, which may be formed by intracontinental subduction, lithosphere delamination, mantle-derived magmatic underplating and mineralization.