基于EIGEN-6C2重力场模型反演青藏高原地壳结构

Tectonic Characteristics of the Tibetan Plateau Based on EIGEN-6C2 Gravity Field Model

重力数据是地下场源产生的重力场的叠加,包含了地下从浅部到深部的丰富信息.高阶卫星资料的丰富为青藏高原深部构造研究提供了重要资料.基于EIGEN-6C2模型作为原始数据,首先对青藏高原布格重力异常和均衡重力异常分别作1～5阶尺度分解,得到不同尺度重力异常的分布特性,探讨不同空间尺度反映的地壳构造意义.其次,基于径向对数功率谱估计平均深度方法理论,进一步研究1～5阶细节反映的场源深度.再次,利用Canny算子的多尺度边缘检测识别和分析重力异常中表现不明显的断裂,定位断裂在地表的位置,识别青藏高原内部断块边界,完成活动块体和次级块体的划分.最后,对布格重力异常进行沉积层及岩石圈改正,采用Parker-Oldenbarg三维位场反演法反演青藏高原莫霍界面起伏。

Gravity anomaly data are the results of gravity force field by all underground sources, including information in the shallow and deep parts of the earth. The studies of satellite gravity field have been increased in recent years, which provide im- portant information for the study of deep structures under the Tibetan Plateau. Using EIGEN-6C2 gravity field data, we first analyze the Bouguer gravity anomaly and isostatic gravity anomaly from one to five scale decomposition based on multi-resolution analysis method. Then distribution characteristics of gravity anomaly sources in different depths are evaluated with the help of other geophysical factors, in order to recover the geometric characteristics in different scale. Second, we estimate the approx- imate depths of the geologic bodies using the power spectral analysis on the decomposed anomalies from first to fifth order. Third, the edge detection method based on Canny operator is employed to identify the undistinguished fractures, to further de- termine the block boundary in the Tibetan plateau and to divide blocks and sub-blocks that are active tectonically. Final, after sedimentary and lithosphere corrections, the three dimensional Parker-Oldenbarg inverse theory on the Bouguer anomaly is ap- plied to invert Moho depths in Tibetan plateau.