Abstract:

Yushan-Kume fault belt,situated along Yushan Archipelago of Eastern Zhejiang coast and Kume Islands in the west side of Kyukyu Archipelago,across the central part of East China Sea the strike direction of 300-305?,more than 1000km long and 100km wide,consists of three factures of Yushan-Kume,Yuzhong-Niaodao and Taohua-Suguo.It shows a relative high value zone on both gravity and magnetic maps,and a horst structure on a seismic profile section,the dip angle of which are about 70-80皌o NNE and SSW,the fault throw about 540-2260m respectively.The sea bottom topography in Okinawa Trough presents a uplift towards NWW.The belt is considered to be a normal anticlockwise fault with its north block moved westwards and south block eastwards,the offset distance is about 5-50km.The distribution of basalts can be found on the west part of the belt,showing that the belt has deeply cut the earth crust.The belt is huge to the west,which expands to the northeast of Zhejiang,passing through Kyukyu Trench to Okidaito Isiands of the west Pacific Ocean.The belt has been intensely activating since its formation in Cretaceous.The formation and development of wich is a result of the underthrusting of the Pacific Plate towards Eurasia Plate,and the creeping of Chinese Continental margin continously eastwards.It has played a role of dividing structural features of East China Sea into south and north sea area.The geophysical fields,sea floor features,Cenozoic sediments,major structural direc-tions,reginal structures,fault characteristics,volcanicities,the value of thermal flow in the sea floor and Moho depth within the south and north part of East China Sea are distinctly different.