基于重力梯度结构张量特征值斜导数边界识别方法及其在南海的应用

边界识别对地质构造解释具有十分重要的意义，其可以指出地下断层、接触带和其他构造单元的边界位置.现有的边界识别滤波器大多数基于重力梯度数据及其水平和垂直导数.然而，这些传统方法具有一定的局限性，对噪音的敏感，且不能有效的均衡深浅异常的振幅，尤其是当测量异常中同时出现正异常和负异常将产生假的边界结果，对后期构造解释带来误导.针对传统方法的缺点，本文提出Tilt-Eigen边界识别方法，利用重力梯度结构张量矩阵特征值通过倾斜角计算结果的最大值实现边界识别.通过理论模型试验，该方法不仅能均衡深部浅部振幅异常的边界，避免引入额外的虚假边界异常，且识别的边界结果更加准确、收敛.将Tilt-Eigen方法用于南海实际重力数据处理，获得了20条比较清晰的边界结果.根据这些边界结果，本文推断红河断裂往ES方向延伸到南海南部区域后，开始朝正南方向延伸，与越东万安断裂相连接；推断出南沙海槽东北部为古南海缝合带，而其西南部并不是缝合带，缝合带位于其南侧的文莱沙巴附近；将南海分为8个地质构造单元.

The edge detection method and its application in the south China sea based on the gravity gradient structure tensor eigenvalue

Boundary identification is of great significance to the interpretation of geological structure and can point out the horizontal position of underground faults, contact zones and other boundaries. Most of the existing boundary recognition methods are based on gravity horizontal and vertical derivatives. However, these traditional methods have certain limitations, are sensitive to noise, and cannot be effectively balanced depth anomaly amplitude, especially when there are positive and negative anomaly at the same time, and which will produce the false boundary, and bring misleading later structure explanation. Aiming at the shortcomings of traditional methods, this paper proposes an algorithm called Tilt-Eigen method which identifies the boundary through the maximum value of the calculated result of the Tilt Angle. Theoretical model test shows that this method can not only balance the boundaries of the deep and shallow anomaly, avoid introducing additional false boundary anomaly, but also can result more accurate and convergent boundary. The Tilt-Eigen method is used for the actual gravity data in the south China sea, and 20 clear boundary results are obtained. According to these boundary results and geological analysis, this paper concludes that the red river fault extends to the southern region of the south China sea, and then connects with the Yuedong Wanan fault. The southeast part of the Nansha Trough is the ancient South China Sea suture, and its southwestern part is not a suture zone,whereas suture zone is near the north of Brunei Saba. The south China sea can be divided into eight geologic tectonic units.