Based on a data base of multi-channel seismic profiles covered over Dongsha plateau of the northern South China Sea margin, we found that the sea bed morphology of northern South China Sea margin had been changed dram...Based on a data base of multi-channel seismic profiles covered over Dongsha plateau of the northern South China Sea margin, we found that the sea bed morphology of northern South China Sea margin had been changed dramatically after Dongsha uplifting, that sedimentary layer since Miocene age had been eroded with maximum eroded thickness more than 1000 m, and that an erosive channel had been formed of 20 km in width and 200 km in length and several hundreds meters in depth on the outer shelf of northern South China Sea. The erosive channel is parallel to the 600 m isobath line, stretching from northeast to the southwest north of Dongsha uplift. The Kuroshio intrudes the South China Sea through Luzon Strait both in winter time and summer time, and in the northern South China Sea margin area, the intruded Kuroshio Branch takes the form of Pacific-Indian Ocean Through Flow (PITH) in winter time, while the Luzon Strait Subsurface Inflow (LSSIF) in summer time, the routes of both PITH and LSSIF coincide well with the distribution of the erosive channel. After climbing from the northern slope up to the northern shelf, and after joined by the southward flow from the middle northern shelf of South China Sea, the Kuroshio Branch is strengthened and thus is able to erode the sea floor, and the shape of the erosive channel is a result of the long-term interaction between the Kuroshio South China Sea Branch and the Dongsha outer shelf sea floor.展开更多
3D structure of the crust and upper mantle in the studied area has been analyzed from surface wave tomography. The velocity distribution in the uppermost crust is symmetrical on two sides of the central line of the se...3D structure of the crust and upper mantle in the studied area has been analyzed from surface wave tomography. The velocity distribution in the uppermost crust is symmetrical on two sides of the central line of the sea, and coincides with the structure of crystalline basement. The essential difference in tectonics between the East China Sea and the Yellow Sea mainly lies in that the velocity structures of their lower crust and upper mantle are identical to those of South China and North China respectively. In the upper mantle there exists a high-velocity zone with a nearly EW strike from the Hangzhou Bay, China, to the Tokara Channel, Japan, along about the latitude of 30°N. It is found that between the East China Sea and the Yellow Sea there are systematical differences in geomorphology, geology, seismicity, heat flow, quality factor and gravity and aeromagnetic anomalies, which is related to both left-lateral shear dislocation and right-lateral tear of the Benioff zone from the Hangzhou Bay to the Tokara Channel.It is inferred that the East China Sea was formed by Cenozoic back-arc extension. The boundary between the North China and South China crustal blocks stretches along the southern piedmont of Mts. Daba-Dabie-Hangzhou Bay-Tokara Channel, and the subduction zone at the Okinawa trench is the eastern boundary of the South China crustal block. The movements of the Pacific plate, Indian plate and upper mantle rather than the Philippine plate subduction have played a dominant role for the modern tectonic movements in East Asia.展开更多
The unsteady flow in the Middle Route South-to-North Water Transfer Channel was simulated numerically using an implicit solution procedure for the Saint Venant equations. An equivalent roughness was used to simulate t...The unsteady flow in the Middle Route South-to-North Water Transfer Channel was simulated numerically using an implicit solution procedure for the Saint Venant equations. An equivalent roughness was used to simulate the effect of many transfer structures on the water levels in the main channel. Various gate operating and control methods were analyzed to study the response to disturbances produced by varying the flow rates through the Tianjin outlet. The results show that when the inflow at the head changes in the same way as the sum of the flow rates through all the outlets, the transition time and the fluctuation of the water levels using the timed gate operation method are less than when using the simultaneous gate operation method, but the variations of the gate openings and flow rates through each control gate are much larger. The flow disturbances produced by the Tianjin outlet can be rectified within several channel sections and the transition time can be greatly shortened by allowing the water levels immediately upstream of the control gates to vary within proscribed ranges, rather than being held constant.展开更多
基金supported by National Basic Research Program of China (Grant No. 2007CB411702)
文摘Based on a data base of multi-channel seismic profiles covered over Dongsha plateau of the northern South China Sea margin, we found that the sea bed morphology of northern South China Sea margin had been changed dramatically after Dongsha uplifting, that sedimentary layer since Miocene age had been eroded with maximum eroded thickness more than 1000 m, and that an erosive channel had been formed of 20 km in width and 200 km in length and several hundreds meters in depth on the outer shelf of northern South China Sea. The erosive channel is parallel to the 600 m isobath line, stretching from northeast to the southwest north of Dongsha uplift. The Kuroshio intrudes the South China Sea through Luzon Strait both in winter time and summer time, and in the northern South China Sea margin area, the intruded Kuroshio Branch takes the form of Pacific-Indian Ocean Through Flow (PITH) in winter time, while the Luzon Strait Subsurface Inflow (LSSIF) in summer time, the routes of both PITH and LSSIF coincide well with the distribution of the erosive channel. After climbing from the northern slope up to the northern shelf, and after joined by the southward flow from the middle northern shelf of South China Sea, the Kuroshio Branch is strengthened and thus is able to erode the sea floor, and the shape of the erosive channel is a result of the long-term interaction between the Kuroshio South China Sea Branch and the Dongsha outer shelf sea floor.
基金The study (Project No. 85078) was supported by the Joint Foundation of Seismic Science.
文摘3D structure of the crust and upper mantle in the studied area has been analyzed from surface wave tomography. The velocity distribution in the uppermost crust is symmetrical on two sides of the central line of the sea, and coincides with the structure of crystalline basement. The essential difference in tectonics between the East China Sea and the Yellow Sea mainly lies in that the velocity structures of their lower crust and upper mantle are identical to those of South China and North China respectively. In the upper mantle there exists a high-velocity zone with a nearly EW strike from the Hangzhou Bay, China, to the Tokara Channel, Japan, along about the latitude of 30°N. It is found that between the East China Sea and the Yellow Sea there are systematical differences in geomorphology, geology, seismicity, heat flow, quality factor and gravity and aeromagnetic anomalies, which is related to both left-lateral shear dislocation and right-lateral tear of the Benioff zone from the Hangzhou Bay to the Tokara Channel.It is inferred that the East China Sea was formed by Cenozoic back-arc extension. The boundary between the North China and South China crustal blocks stretches along the southern piedmont of Mts. Daba-Dabie-Hangzhou Bay-Tokara Channel, and the subduction zone at the Okinawa trench is the eastern boundary of the South China crustal block. The movements of the Pacific plate, Indian plate and upper mantle rather than the Philippine plate subduction have played a dominant role for the modern tectonic movements in East Asia.
基金Supported by China Postdoctoral Science Foundation (No. 20060390078)
文摘The unsteady flow in the Middle Route South-to-North Water Transfer Channel was simulated numerically using an implicit solution procedure for the Saint Venant equations. An equivalent roughness was used to simulate the effect of many transfer structures on the water levels in the main channel. Various gate operating and control methods were analyzed to study the response to disturbances produced by varying the flow rates through the Tianjin outlet. The results show that when the inflow at the head changes in the same way as the sum of the flow rates through all the outlets, the transition time and the fluctuation of the water levels using the timed gate operation method are less than when using the simultaneous gate operation method, but the variations of the gate openings and flow rates through each control gate are much larger. The flow disturbances produced by the Tianjin outlet can be rectified within several channel sections and the transition time can be greatly shortened by allowing the water levels immediately upstream of the control gates to vary within proscribed ranges, rather than being held constant.
