Crustal velocity structure imaging and tectonic characterisation in Liaoning Province, China

This study analyzes near-seismic data from January 2008 to December 2022, extracting first-arrival wave travel times of P and S waves from 3946 natural earthquakes. A 3D fine-structure model of Vp and Vs for the Liaoning area is constructed using the regional-scale double-difference tomography (tomoDD) method. The results reveal that: (1) Shallow crust velocity structures align with geotectonic features, with low-velocity anomalies in basins and high-velocity anomalies in mountainous areas. (2) Significant low-velocity anomalies in the middle and upper crust are found in the Chaoyang-Yixian, Lower Liaohe, Wafangdian, and Liaodong Volcanic-Sedimentary Basins, likely linked to low-density, water-bearing granodiorite rocks. (3) Vertical profiles show complex, laterally inhomogeneous crustal velocity structures, with seismic events concentrated in low-velocity bodies or transition zones. This is related to the thinning of the North China Craton, where thermal upwelling has weakened the crust, facilitating earthquake initiation. These findings provide new insights into the region’s geodynamics and have implications for seismic hazard assessment.