Uppermost Mantle Seismic Pn‐Velocity in Continental China and Its Tectonic Implications

Abstract

AbstractWe construct a high‐resolution Pn‐velocity model in continental China through a new tomographic scheme simultaneously inverting event epicenter location and Pn‐velocity and accurately accounting for the Pn propagation effects of irregular crustal thickness variation. The inversion integrates a combined data set of 32,427 absolute Pn travel times and 62,431 interstation Pn differential travel times manually picked from the recordings of 2,989 stations in and around continental China, yielding a model of spatial resolutions ranging from 0.75° × 0.75°–3° × 3°. Major Pn‐velocity features revealed by the model and the tectonic processes we attribute to include: (a) high Pn‐velocities beneath major cratonic blocks and the southern Tibetan Plateau attributed to low temperatures of cratons, (b) low Pn‐velocities beneath the eastern North China craton around the Tan‐Lu fault and the central South China block attributed to high temperatures and low‐Mg# () peridotites in response to the Mesozoic‐Cenozoic subduction of the Pacific plate, and beneath the Trans‐North China orogen, most regions of the Tibetan blocks and the central Tianshan orogen attributed to high temperatures after multiple tectono‐thermal events in response to the Mesozoic‐Cenozoic subduction of the Pacific plate, the Triassic convergence of the North China, Yangtze, and northern Tibetan blocks and the Cenozoic India‐Eurasia collision, and (c) intermediate Pn‐velocities beneath the marginal regions of the Ordos block and Micang‐Daba region attributed to possible extrusion of hot asthenospheric flow from the Tibetan Plateau in response to far‐field effects of the India‐Eurasia collision.