Constraints on the evolution of East Asia's mantle from P-wave travel time tomography

High resolution tomographic images of the mantle structure beneath East Asia have been obtained through inversion of travel time data from global and regional seismograph stations and regional (temporary) arrays. These data resolve three-dimensional (3-D) upper mantle heterogeneity in unprecedented detail. In the west, high velocity anomalies are dominant beneath the Himalayas and the western portion of the Tibetan plateau to 300 km depth, which we interpret as the image of the northeastward subducting Indian lithospheric mantle. In contrast, P-wave tomography does not provide evidence for underthrusting of the Indian lithosphere beneath much of central and eastern Tibet. Beneath East China, slabs subducting from the Japan and Izu-Bonin trenches are deflected in the mantle transition zone. These stagnant slabs likely influence upper mantle convection beneath East Asia and might be related to volcanism in Korea and northeast China (such as the Changbai volcanic area). Low wavespeed structures in the shallow mantle beneath the Red River fault region connect to deep, slow anomalies beneath the South China Foldbelt. Tomographic imaging also reveals high wavespeed continental roots of the Precambrian Ordos block and Sichuan Basin (to 250-300 km depth) and strong heterogeneity between the latter and the Burma ranges further to the west. Together these structures may mark a transition in tectonic regime from the continental collision control in the west to control by subduction of Pacific, Philippine Sea and Indonesia plates to the east and the southeast.