Mantle S Wave Tomography Beneath China Using Absolute Travel Time Residual

We conducted the shear wave tomography of mantle beneath China and adjacent areas using absolute travel time residual of ISC(International Seismological Center)data and CEA(China Earthquake Administration)data from local earthquakes and teleseismic events.It can solve the problems of mantle heterogeneity outside the targeted areas and the resulting model's zero mean as opposed to relative travel time residual.Error of ISC data is estimated by summary ray method of calculating the standard deviation of all the travel time residuals within nearby events for every station,the extent to which the robustness of ISC data can be promoted effectively.Compared the results of synthetic test obtained by the ISC data and ISC + CEA data respectively,the resolutions of Cratons and slabs are significantly improved by combination of two datasets.From the resulting model,the upper mantle beneath China are widely dominated by the slow anomalies.Deeply rooted fast anomalies are observed beneath the stable Yangtze craton and Ordos craton and they may play a role in stability of the blocks.Another fast anomaly observed in India-Eurasia collision belt extends down to the depth of 200km-300km to which it may represent that the India slab has subducted down beneath Tibetan Plateau.The upper mantle beneath Tibetan plateau is almost surrounded by adjacent fast anomaly due to probable surrounding strong blocks.The large slow anomaly beneath South China Block may be related to thermal anomaly and partial melt.The subducted pacific slab is clearly imaged as fast velocity anomaly down to about 660km and it is extending to lower mantle.