摘要
东海陆架前缘斜坡(冲绳海槽西坡)北部的断块隆脊,是呈长条形的脊状台式隆起,位于29°30′N-31°10′N;128°00′E-128°20′E之间。其由NNE向链状排列的断块山地组成,且与NNE向的断裂构造相一致,其顶部水深约300m～400m左右。从实测单道地震剖面看,隆脊的东西两侧均有断层出现。隆脊西坡倾向陆架一侧,坡度大,有的地方坡度超过10°;而东侧坡度较缓,仅1°左右,缓倾至海槽西坡坡底,并以沟坎式与冲绳海槽槽底相连。冲绳海槽地区的构造运动,使隆脊地区受到断裂构造的作用。NNE向的大断裂使该隆脊位置的东西两侧断裂下降而中间抬起,加之下部岩浆上侵,显现出链式排列的断块山地,表现为一条长形的断块隆脊构造地貌体。推测该地貌体形成的时期较晚。
The rift block ridge in the north continental shelf front slope of the East China Sea, discussed in this paper, is a stripe of ridged platform uplift, which is composed of a chain of rift block mounts extending in the NNE direction, consistent with the run of the fault structure in the area. It lies in the latitude of 29°30'N to 31°10'N and longitude of 128°00'E to 128°20'E, in water depths of about 300m to 400m for its top surface. On the seismic profile, some big faults can be found on both sides of the ridge. The west side of the ridge slopes to the side of the continental shelf steeply, with a big gradient of over 10° in some places; the east side of the ridge slopes downward gently to the foot of the west slope of the Okinawa Trough, with a relatively very low gradient of about 1°, being connected with the Trough bottom through scarps and gullies. The formation of the block ridge is due to tectonic movement of the Okinawa Trough, which makes the region concerned undergo fault tectonic activity. The big faults in the NNE direction make the seabed on both sides of the ridge area decline while the middle part (the ridge area) rise. Meanwhile, the upward intrusion of magma also contributes to the formation of the ridge. As a result of the joint action, a chain of rift block mounts are formed, appearing as a long narrow rift block ridge as a whole. Therefore, it is supposed that the rift block ridge was formed at the time when the faults on both sides of the ridge occurred and the forming time was very late.
基金
中国科学院重大项目!( 5 2 1 0 4 5 6号 )资助
关键词
东海
陆架前缘斜坡
断块隆脊地貌
冲绳海槽
the continental shelf front slope of the East China Sea
rift block ridge
geomorphology
tectonism
Okinawa Trough
