用于塔里木地壳构造成像的重力场谱矩方法研究

A study on spectral moments of gravity field with application to crustal structure imaging of Tarim basin

现代地壳探测取得的各种地球物理场中包含有大量地壳构造信息,如果提取这些信息,可以在数学物理普适规律指导下计算出关于地壳构造的图件.由于区域重力场的高阶谱矩包含了场轮廓面的几何信息,可用于地质构造要素的分析计算,为地质构造要素选取和定位的计算机自动制图提供理论依据.由地面布格重力场的二阶谱矩的统计不变量计算,可导出表征地壳变形带的脊形化系数,用于计算机自动制作区域地壳变形带分布图.脊形化系数强弱区的边界代表了活动的和稳定的构造单元的边界.在计算脊形化系数的基础上,还可进一步计算其二阶谱矩的统计不变量并作进一步增强处理,计算构造单元的边界系数,对地壳构造单元边界作连续和精细的追踪.文中介绍了脊形化系数和边界系数的计算方法,以及用在塔里木盆地进行地壳构造分析的结果.圈定了塔里木盆地深层满中高密度扰动带和满南、满北低密度扰动带,为深层油气勘探提供重要基础资料.

Modern geophysical techniques provide great amount of geophysical field data that contain rich information about crustal structures, which can be extracted for geo-mapping based on the theory of mathematical physics. This paper shows that the high-order spectral moments of regional gravity data include information of geometrical contour surface, which can be used for selection, positioning and classification of some types of geological structures. By using second-order spectral moments of Bouguer gravity data, one can calculate their statistical unvaried quantities and the ridge-like parameter, which characterizes the crustal deformation belts and can be used for mapping regional distribution of the deformation belts. The boundaries between areas of strong or weak ridge-like parameters represent boundaries of different structural units. We can further compute the second-order spectral moments of the ridge-like parameter surface to calculate the boundary parameter, which may be used for tracing and positioning the structural boundaries after some enhancement is added. This paper gives all the formulae for computing the ridge-like and the boundary parameters, and the testing results of crustal structural analysis in Tarim Basin, Northwest China. As a result, the deep High- and Low-density belts within the Tarim Basin are located precisely, providing important basic images for oil/gas exploration in the basin.