Numerical simulations on deep subduction of western Pacific plate to NE China

Using temperature-dependent viscosity and considering depth difference between oceanic plate and continental plate, We discuss numerically the possible geodynamical process for tomography results in NE China with convergence velocity of Pacific plate and Eurasian plate and multiple trench retreating models. The results front Our models show that trench retreat is necessary for reproducing the flat lying slab as observed by tomography under NE China. Occurrence of lying slab on 660 km phase change boundary is mainly Clue to the higher viscosity contrast between lower mantle and upper mantle. The subduction of the Pacific plate to Eurasian plate is most likely to have Occurred before 70 Ma B. P., the trench retreating velocity is probably variable but Must be less than 45mm/a which is estimated by sonic geologists. As to the reason of trench retreat. our simulation results indicate that the possible force for trench retreat is the eastward asthenospheric flow and pushing effect under the continental lithosphere which may be related to India-Eurasia collision. so the extensional tectonic features Must be, attributed to the total effects of India-Eurasia collision and Pacific-Eurasia convergence.