Seismic mapping of the central and southern segments of the Tanlu fault zone using P-wave receiver functions

The central and southern segments of the Tanlu fault zone, located in the collision boundary between the Yangtze Plate and the North China Craton, underwent complex tectonic deformation associated with the Pacific Plate subduction. The crustal thickness and Vp/Vs ratio are important parameters for comprehending tectonic evolution and geodynamic processes. By integrating a newly dense seismic array, our results based on P-wave receiver function analyses reveal the crust thickness varies significantly across the Tanlu fault zone. The Yangtze Plate is characterized by a thinner crust, contrasting a thicker crust imaged in the North China Craton, indicating the Tanlu fault zone is a prominent structural block boundary. The Vp/Vs ratio within the Tanlu fault zone is visibly higher than its surroundings, probably correlating with abundant fluids activity along the fault zone, as a result of the subduction of the Pacific Plate. Additionally, we observe a gradually deepening Moho discontinuity beneath the Sulu orogenic belt with a low-angle dip, presenting direct seismic evidence for supporting the ancient Yangtze Plate underthrusting beneath the Sulu orogenic belt.