Stress Drop Variability and Rapid Fault Activation in Hydraulic-Fracturing-Induced Earthquakes: Insights from the Southern Sichuan Basin

Hydraulic fracturing operations in the Southern Sichuan Basin have generated significant induced seismicity, raising important questions about the underlying rupture processes. We analyze stress drops of 3,369 induced earthquakes (ML > 0.5) using a non-parametric generalized inversion technique with rigorous reference-station corrections. Our analysis reveals two key characteristics of these induced events: first, they exhibit systematically low stress drops (median 0.07 MPa) that show positive scaling with seismic moment, challenging classical self-similarity assumptions; second, we observe pronounced spatial variations in stress release that correlate with depth and fault structure. Notably, fluid diffusion drives rapid activation of fault asperities, resulting in repeated high-stress-drop ruptures (0.3-6.0 MPa) within short timescales of days. This accelerated rupture cycle differs fundamentally from tectonic earthquake recurrence patterns. Our findings demonstrate that induced earthquake rupture dynamics are controlled by the interplay of heterogeneous fault strength and rapid fluid pressurization, providing critical insights for developing targeted hazard assessment strategies in energy-producing regions.