Insight into seismotectonics of the central-south Tanlu Fault in East China from P-wave tomography

Abstract

The Tanlu Fault is a significant fault in East China that has been associated with numerous destructive earthquakes in its central-south segment. However, the mechanisms behind these earthquakes remain unclear. This study aims to shed light on the seismic velocity structures of the crust and upper mantle under East China and their influence on the region's seismotectonics. Our findings reveal that the upper mantle structures play a crucial role in regional seismotectonics. The 1668 Tancheng earthquake (M 8.5) is located above remarkable upper-mantle high-velocity bodies on both sides of the Tanlu Fault. Thus, it was likely produced by the interaction between the North China and Yangtze plates, with the lithospheric mantle significantly affecting the plate interaction. Another group of earthquakes of magnitude M 5–6 is located in the Subei–Yellow Sea Basin (SYSB). We have imaged a low-velocity body in the upper mantle, which is believed to represent hot and buoyant materials under the SYSB. This anonymous body may reduce the vertical stress in the crust and provide fluids to fault planes, thereby facilitating moderate-to-large earthquakes in the crust. These new findings provide valuable insight into the seismotectonics of East China, particularly the role of the upper mantle structures in shaping the region's seismic activity.