Quantifying the Role of Fluid Injection in Induced Seismicity at Changning Salt Mine

Understanding the causal mechanisms linking industrial fluid injection to induced seismicity is crucial for seismic hazard assessment. This study investigates the relationship between salt-mining operations and anomalous seismicity in Changning, Sichuan, China. We use two independent approaches: (1) calculating static Coulomb stress changes induced by fluid injection/extraction; (2) estimating stress perturbations via rate-and-state friction law. Key findings reveal that within 2 km of the wells, injection-induced stress perturbations promoted seismicity. Spatiotemporal correlation with positive Coulomb stress changes confirms injection modulated near-field fault stability. Beyond 2 km, minimal injection-induced stresses preclude direct triggering. Instead, external large events and cascading stress transfer from near-field earthquakes may dominate the mid- to far-field seismicity. Critically, cumulative seismic moment release exceeded the theoretical bound, demonstrating that tectonic processes supplied considerable seismic energy. The dual-path stress analysis quantifies injection’s fractional role and effectively evaluates the impact of fluid injection in complex geological settings.