摘要
提出根据区域重力异常计算地壳表层视密度分布的方法。依据原观测平面异常与延拓到某一高度平面异常的差值场所具有的突出浅源异常、压制深源异常的特点 ,按维纳滤波原理 ,应用多层格林等效层模型精确模拟该差值重力场的径向对数功率谱 ,设计重力场在频率域进行异常分离的具有自适应性的优选延拓算子 ,实现垂向异常分离。利用重力场可看成由许多等效直立棱柱体叠加的原理 ,在频率域内 ,通过换算重力场的一次导数 ,计算出视密度的分布。用上述方法处理中国布格重力异常图 ,获得了中国地壳表层 0 10km剩余重力异常 ,并成功编制视密度图。比较表明 ,视密度的分布特征与大地构造单元及分区有较好的对应关系。地壳表层的岩石密度分布的获得 ,为中国的基础地质与构造研究提供了重要依据。
An apparent density mapping from gravity anomaly and a comparison of the mapping with the tectonic outline map of China are presented. A subtraction of upward continuation of gravity anomaly to a certain height from anomaly at observation level enhances short wavelength signal due to shallow layer of the crust with a thickness that equals to the height. A preferential continuation operator derived from Wiener filter and Green’s equivalent layer principles is used to separate the anomaly caused by the shallow layer from observed anomaly. An inversion using a series of right rectangular prisms and computation of the first derivative of gravity anomaly is applied to transform the anomaly due to the shallow\|layer yielded by the subtraction and the preferential continuation into a density map. By means of the above method the gravity anomaly attributed to the upper crust with a thickness of 10 km is separated from the Bouguer gravity of China and an apparent density mapping of China is derived. A comparison of the mapping with the tectonic outline map of China shows that characteristics such as closed density maxima (density high) or closed density minima (density low) of apparent density on the mapping well correspond to known tectonic units and geomorphological units, such as collision zone between plates, fault\|magmatic belts, basins, stable blocks and granitic distribution areas.
出处
《地学前缘》
EI
CAS
CSCD
2001年第2期407-413,共7页
Earth Science Frontiers
基金
国家自然科学基金!资助项目 (49772 14 9)
