Double-difference tomography in the Qinling orogenic belt and its adjacent areas

The Qinling orogenic belt and its adjacent areas serve as the convergence zone between the North China craton, the Yangtze craton, and the northeastern edge of the Qinghai-Xizang Plateau are characterized by complex tectonic activity. This study utilizes observational data from 159 fixed stations of the China Earthquake Administration in Shaanxi, Sichuan, Gansu, and other regions, as well as 182 broadband mobile stations from the ChinArray Ⅱ project. We obtained a three-dimensional velocity structure of the Qinling orogenic belt and its adjacent areas by employing the double-difference tomography method. The imaging results reveal that the crustal thickness of the Hanzhong basin is approximately 38 km, and the Moho interface exhibits a dome-like shape, convex in the center and concave on both sides. Additionally, a significant low-velocity anomaly is observed along the northern edge of the western Qinling orogenic belt and the southern side of the Longxian-Baoji fault zone, extending to a depth of approximately 39 km. This anomaly is associated with the eastward flow of materials from the middle and lower crust of the Qinghai-Xizang Plateau.