Some new understandings on deep structure in Yellow Sea and East China Sea

Yellow Sea and part of East China Sea are chosen as the research region (26 degrees N similar to 36 degrees N, 120 degrees E similar to 130 degrees E) to discuss the deep structure and the relationship with adjacent geological units via tomography and gravity, magnetic inversion. Two density structure profiles are obtained after inversion. In East China Sea Continental Shelf region, the crust thickness doesn't change obviously. The thickness of crust begins to thin evidently in Okinawa Trough and middle crust disappears there. In Ryukyu Island Arc region, the crust thickness increases again and upper crust increases most obviously. We deduce that it is relative with the movement difference between plate and mantle around subduction zone. "Belt geophysical anomaly in longitude direction" is obvious symbol in research area and it is also the reflection of crust structure from West to East. With the increase of depth, tectonics in EW direction in lithosphere becomes the preponderance tectonic system. It is deduced that they are from collision and compression process of plates in Triassic but anomaly belts in NE direction are the reflection of later movement in shallow part of lithosphere. Unharmonious phenomena between deep and shallow preponderance tectonics exist in lithosphere of research region. The seismic tomography results from plane and profile not only approve the existence of East Marginal Fault Zone of South Yellow Sea but also give the attitude of that Shaoxing-Shiwandashan collision belt is a high velocity belt and it inclines to NW direction with 40 degrees dip angle. Another high velocity belt with almost the same direction of dip is the image of the boundary between Southern and Northern Yangtze Block in deep.