3-D velocity model of the crust and uppermost mantle beneath Xinjiang region, constructed by joint tomography of body and surface wave data

The Xinjiang region is situated between the Tethyan and Central Asian orogenic belts. It has undergone multiple episodes of accretionary orogenesis and was tectonically reactivated during the Cenozoic by the far-field compressional effects of the India-Eurasia continental collision. These processes have generated pronounced seismicity and recurrent earthquake-related hazards in this region. A high-resolution three-dimensional velocity model is essential for multi-scale velocity model construction, source-parameter inversion, simulation of strong ground motion, and seismic hazard assessment. In this study, we collected first-arrival body-wave travel-time data recorded by permanent stations in and around Xinjiang and processed both ambient-noise and regional-earthquake surface-wave records. The resulting dataset comprises ~8.1 million body-wave travel-time picks—including absolute arrival times and event-pair differential times—and ~5,000 surface-wave dispersion curves (5–50 s period). By joint inversion of these complementary body and surface wave datasets, we determined a high-resolution three-dimensional Vp and Vs model for the crust and uppermost mantle beneath Xinjiang (XJVM-1.0) with a lateral resolution of 50–100 km and a vertical resolution of ~10 km. XJVM-1.0 reveals that the Tianshan orogen exhibits a relatively rigid upper crust that hosts abundant seismicity under far-field compression, whereas its middle-lower crust accommodates the majority of compressional stress through plastic deformation and/or partial melting. In contrast, the interiors of the Junggar and Tarim basins have experienced negligible internal deformation and are inferred to underthrust beneath the Tianshan orogen in response to the India-Eurasia collision. Relocated seismicity indicates that earthquakes are predominantly concentrated within the Tianshan range, with a notable proportion occurring in the middle-lower crust, implying whole-crust tectonic activity and highlighting the potential for great earthquakes in this region.