Stephan Tobias, Enkelmann Eva, Kroner Uwe
Department of Geoscience, University of Calgary, Calgary, AB, T2N 1N4, Canada.
Department of Geology, Lakehead University, Thunder Bay, ON, P7B 5E1, Canada.
Sci Rep. 2023 Sep 20;13(1):15590. doi: 10.1038/s41598-023-42433-2.
The spatial analysis of horizontal stress orientation is important to study stress sources and understand tectonics and the deformation of the lithosphere. Additional to the stress sources, the geometry of stress fields depends on the underlying coordinate reference system, which causes spatial distortions that bias the analysis and interpretation of stresses. The bias can be avoided when the stress field is decomposed and transformed into the reference frame of its first-order stress source. We present a modified and extended theory based on the empirical link between the orientation of first-order stresses and the trajectories of lateral plate boundary forces. This link is applied to analyze the orientation of horizontal stresses, their patterns, and tectonic structures from the perspective of their first-order source or cause. By using only parameters for the relative motion between two neighboring plates, we model the first-order orientation of the maximum horizontal stress that statistically fits the orientation of [Formula: see text]80% of the global stress data adjacent to plate boundaries. Considerable deviations of the observed stress from the predicted first-order stress direction can reveal the geometry of second-order stresses and confine areas where other stress sources dominate. The model's simple assumptions, independence from the sample size, potential application to regional to global scale analysis, and compatibility with other spatial interpolation algorithms make it a powerful method for analyzing stress fields. For immediate use, the presented method is implemented in the free and open-source software package tectonicr, which is written in the computer language R.
水平应力方向的空间分析对于研究应力源、理解构造以及岩石圈的变形非常重要。除应力源外，应力场的几何形状取决于基础坐标参考系统，这会导致空间扭曲，从而使应力分析和解释产生偏差。当应力场被分解并转换为其一阶应力源的参考系时，这种偏差可以避免。我们基于一阶应力方向与板块边界侧向力轨迹之间的经验联系，提出了一种改进和扩展的理论。这种联系被用于从一阶源或成因的角度分析水平应力的方向、其模式以及构造结构。通过仅使用两个相邻板块之间相对运动的参数，我们对最大水平应力的一阶方向进行建模，该方向在统计上与板块边界附近80%的全球应力数据的方向相符。观测应力与预测的一阶应力方向之间的显著偏差可以揭示二阶应力的几何形状，并界定其他应力源占主导的区域。该模型的简单假设、与样本大小无关、在区域到全球尺度分析中的潜在应用以及与其他空间插值算法的兼容性，使其成为分析应力场的有力方法。为便于立即使用，所提出的方法在以计算机语言R编写的免费开源软件包tectonicr中得以实现。
