中国东部海区地球物理调查及重磁场特征

中国海洋地质调查始于20世纪50年代,大致分为创业阶段、起步阶段、发展阶段、全面发展阶段和蓬勃发展阶段,经过多年的地质与地球物理调查,获取了大量的地质地球物理资料。该区磁场强度一般为±200 nT,局部达到±500 nT以上,呈NE、NNE向作带状分布,局部异常走向不一,类型多变。空间和布格重力异常总体走向为NE向,陆区以负异常为主,海区主要表现为正异常,空间重力异常值总体上为-45~+100 mGal,局部异常值可达+200 mGal以上;布格重力异常极小值为-140 mGal,极大值可达+440 mGal,局部地区分布高值异常圈闭。根据重、磁异常的幅值高低、形态展布和区域变化等特征,将重、磁异常各自划分为华北-渤海异常区、山东半岛-北黄海异常区等9个异常区,重磁场特征充分展示了中国东部海区东西分带、南北分块的构造格局。

GEOPHYSICAL SURVEY IN EASTERN CHINA SEAS AND THE CHARACTERISTICS OF GRAVITY AND MAGNETIC FIELDS

Marine geophysical investigation in China started from 50's of the last century. It could be roughly divided into the starting-up stage, early stage, developing stage, rapid developing stage and accelerated developing stage. A large number of high-resolution geological and geophysical data have been acquired by the surveys in the past years. With regard to the magnetic data, the background of magnetic anomalies is ±200 nT, with some anomalies higher than ±500 nT occurring in some local areas. Most of the anomalies extend in NE or NNE direction in a band pattern. However, some anomalies vary in both types and distribution patterns. Free air and Bouguer gravity anomalies are also showing a NE distribution pattern. In a general view, negative anomalies prevail in land, whereas the sea is dominated by positive anomalies. The intensity of free air gravity anomalies normally vary in the range of -45 and +100 mGal, with some of anomalies higher than +200 mGal in local areas. The intensity of Bouguer gravity anomalies change between -140 and +440 mGal. According to the intensity of gravity and magnetic anomalies, in combination with the characteristics of geomorphology, we may divide the region into nine areas, such as the North China-Bohai magnetic anomaly area and Shandong peninsula-north Yellow Sea anomaly area. The distribution pattern of "zoning in east-west direction and blocking in north-south direction" is rather obvious.