An Improved Method for Inverting the Spatiotemporal Stress Field Using Focal Mechanism Data and Its Application in Sichuan–Yunnan Region, China

This study presents a novel iterative method for inverting regional stress fields from focal mechanism data. Building upon key techniques in homogeneous stress inversion, the method enhances the accuracy of stress estimation. The procedure involves clustering seismic events based on spatial distribution to define discrete stress domains, followed by fault plane identification via a fault instability criterion, thereby relaxing the conventional assumption of uniform shear stress across all planes. Stress continuity between adjacent domains is imposed to ensure a smoothly varying stress field. The method is applied to both synthetic tests and earthquake data from the seismically active Sichuan–Yunnan region of China. Results demonstrate that, while principal stress orientations remain consistent with those obtained from conventional approaches, the proposed method provides more reliable estimates of the stress shape ratio, which align more closely with the regional tectonic framework.