GEOPHYSICAL FIELD AND LITHOSPHERE OF THE LIAODONG BAY

The Liaodong bay is a Cenozoic continental rift developed along the Tanlu Fault. The deep structure constrains the shallow. A detailed summarization and an integrated analysis of gravity field, magnetic field, seismic wave, heat flow, geothermal distribution and lithosphere speed are made for the Laodong bay in the paper. The study demonstrates that the Liaodong Bay is characterized by high deep gravity, relatively low heat flow with shallow Curie isothermal surface and intra-crustal and intra-mantle high conductive layers. The lower average velocity of Pn wave in this area may owe its origin to the heat flow intrusion into the top of upper mantle. Based on the direction of fast wave towards NE-trend, it is inferred that the strike slipping of eastern Liaodong bay is weaker than that of the Laizhou Bay and the Bozhong with the western Liaodong Bay as the weakest close to zero. The crust of the Liaodong Bay is obviously thinning and the uplifted Curie isothermal surface corresponds to the crust thinning area. It is very likely that the extensional detachment occurs in the process of crust thinning.