MSATSI: A MATLAB Package for Stress Inversion Combining Solid Classic Methodology, a New Simplified User‐Handling, and a Visualization Tool

Online Material: Figures of complete stress inversion results. The estimation of the stress‐field orientation from focal mechanisms of earthquakes is a relevant tool to understand crustal mechanics and the physics of earthquakes. In global seismology, Formal Stress Inversion (FSI) is a well‐established technique to study tectonic processes associated with the occurrence of large earthquakes (e.g., Hardebeck and Michael, 2004; Yoshida et al. , 2012). Information on the stress‐field orientation is also relevant for the exploitation of hydrocarbon and geothermal reservoirs. Knowledge of the orientation of the maximum horizontal stress ( σ Hmax) is crucial for reservoir development, such as drilling and leakage risk assessment (Terakawa et al. , 2012; Martinez‐Garzon et al. , 2013). Additionally, the FSI technique may be useful for understanding the physics of rupture processes at a microscale in the frame of rock deformation experiments in the laboratory. In seismological practice, the stress tensor is obtained either from inverting earthquake focal mechanisms or directly from first‐motion polarities. Most of the developed FSI methods share two main assumptions: Estimation of stress‐field orientation is a nonlinear inverse problem that can be solved either directly or linearized. When solving the nonlinear inverse problem, the best‐fitting stress tensor to the group of focal mechanisms is obtained using grid‐search algorithms (Gephart and Forsyth, 1984; Gephart, 1990; Arnold and Townend, 2007) or Monte Carlo sampling‐based optimization methods (Angelier, 1984; Xu, 2004). The linearized inversion scheme is solved by a generally less computationally extensive least‐squares technique (Michael, 1984; Hardebeck and Michael, 2006). Because of …