固体地球物理研究生学术报告第九期(二）

The velocity perturbation, depth extent and lateral boundaries of the Sichuan Basin(SCB) craton are not well constrained by velocity tomography due to smearing and smoothing effects. With waveform data recorded by China National Seismic Network for events occurred at Solomon Island region, we obtain a detailed structure of the high velocity block beneath SCB. This high velocity block extends to a depth of at least 200 km and has a shear velocity perturbation of ~6%. We also notice a strong multi-pathing pattern on S arrivals, which cannot be explained by the high velocity block beneath SCB. To explain the multi-pathed S arrivals, we need to insert a southeastward dipping high velocity block within the top of the lower mantle below southeastern China，the dipping direction is  opposite to the westward subduction history in this region ,whether the imaged high velocity block tie to the Pacific/Paleo-Pacific subduction or the Philippine subduction is not clear.