东海北部虎皮礁邻近海域地磁异常研究

Study on Magnetic Anomalies in the Hupijiao Reef and Adjacent Sea Areas in the Northern East China Sea

虎皮礁临近海域处在南黄海近东西向构造与东海北部NE向构造的结合部,磁异常表现为以下2个特点,即西北部呈NE及东西向强烈变化异常区及东南部弱变化异常区。2个异常区被NE向延伸的诏安-济州岛深断裂分开,两侧磁场面貌不同。结合陆地资料,通过对磁异常的研究可以得到以下2点认识:(1)江绍断裂在进入杭州湾以后并非继续沿NE向延伸至朝鲜半岛南部,而是沿30°50′N线附近转为近东西向向东延伸,东界终止于125°20′E附近;(2)江南古陆并非终止于上海附近,而是继续向东延伸,长江凹陷实际上就是发育于上海以西地区的江南古陆的向东延伸部分。

The Hupijiao Reef and adjacent sea areas are located at the juncture of the nearly east-west trending structure in the southern Yellow Sea and the NE-trending structure in the northern East China Sea, and the magnetic anomalies in the sea area are characterized by an intensely variational magnetic anomaly area in the northwest part and a weakly variational magnetic anomaly area in the southeast part. The two magnetic anomaly areas are divided by the NE-trending Zhaoan-Jizhoudao deep fault, the magnetic anomalies in the northwest part vary intensely with a large gradient and NE and east-west trends, and the magnetic anomalies in the southeast part vary weakly with a small gradient. It is concluded from the terrestrial and marine magnetic anomaly study results that （1） after entering the Hangzhou Bay, the Jiangshao fault does not extend northeastward to the southern Korean Peninsula, but rather extends eastward along the 30°50′N parallel to the sea area near 125°20′E; （2） the Jiangnan paleoland does not end at Shanghai, but father continuously extends eastward, and the Changjiang depression is actually the east extension of the Jiangnan paleoland in the area west of Shanghai.