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

Abstract This study introduces a novel iterative method for regional stress field inversion using focal mechanism data. By integrating key techniques from homogeneous stress inversion, the method enhances the accuracy of stress estimation. Seismic events are first clustered based on their spatial distribution to define distinct stress partitions. Fault planes are then identified using a fault instability criterion, and the conventional assumption of uniform shear stress across all planes is relaxed. Stress continuity between adjacent partitions is also enforced to produce a smooth stress field. The method is applied to both synthetic data and earthquake data from the seismically active Sichuan–Yunnan region of China. Results show that although the principal stress orientations are consistent with those obtained from conventional approaches, the proposed method yields more reliable stress shape ratios that better align with the regional tectonic setting.