MULTI-LAYER TECTONIC MODEL FOR INTRAPLATE DEFORMATION AND PLASTIC-FLOW-NETWORK IN THE ASIAN CONTINENTAL LITHOSPHERE
Wang Shengzu (Institute of Geology, State Seismological Bureau, Beijing 100029)
The study of spatial distribution of earthquake indicates that most hypocenters of shallow earthquakes are concentrated in the upper and middle crust, forming the "seismogenic layer", and, furthermore, the belt- and network-like epicenter distributions in a large area of the central and eastern Asia continent show a unified seismic network system which is composed of two families of large-scale seismic piers that intersect conjugately. According to the geometric characteristics of the network system, such as the orthogonality of the two families of belts, it is revealed further by considering the brittle-ductile transition of rocks and the rationale of plasticity theory that the seismic network in the upper lithosphere is really a response and manifestation of the plastic-flow network in the lower lithosprere including the lower crust and lithospheric mantle. The existence of the unified plastic-flow network system confirms that the main driving force for intraplate tectonic deformation in the central and eastern Asia continent resuits from the compression of Indian plate, while the long-range transmission of the force is carried out by means of the network plastic flow along the lower lithosphere. The plastic-flow network controlling intraplata deformation may be an essential charcteristic of mechanical actions for the continental plates with collision boundaries just like the Benioff's zones for those with subduction bounlaries.