Geodynamic response of Moho relief modes to the channel flow below the Tibetan Plateau: numerical simulation

The crust-mantle boundary (Moho) is not a 'rigid' interface in physics as evidenced by high-precision artificial source deep seismic sounding in the Tibetan Plateau. This interface is not only extremely uneven with large relief, but also cut by a series of deep faults with different sizes and different geometries. Therefore, it should have complex dynamic responses of material motion on the surface and in the deep subsurface. In the common channel flow model, the interface between the lower crust and upper mantle is assumed as a flat boundary, and simplified into a smooth constrained boundary in numerical simulation. This paper adopts 2-D viscoelastic models to simulate the response of the channel flow model by an undulating Moho interface. These models are based On the average velocities of the crust and upper mantle of the Tibetan plateau extracted observational data. The results shows that the effect of channel flow is limited to a small area. The changes of Moho relief can affect the channel flow. The undulating Moho interface enhances the synchronous motion of the lower crust and lithospheric mantle, but in a limited range. The changes of Moho shape produces different influences on horizontal displacements on the surface and the Moho interface. Where the Moho occurs dislocation, the horizontal displacement on the surface begins to significantly reduce, implying decoupling of displacement between the surface and subsurface. The deep dynamic effects of the model and the response of the surface are not of local characters, instead at least regional processes.