Rupture Dynamics of Fast and Slow Earthquakes Controlled by Fluids

Le résumé fourni par la source

Fluids are ubiquitous in fault zones and can control rupture propagation through thermally induced pressurization and shear-induced dilatancy, which modulate pore pressure and thus fault strength. Among the mechanisms proposed for fast earthquakes and slow slip events, fault-zone fluids are particularly relevant to both behaviors. However, a theoretical rupture-tip equation of motion for elongated faults of finite width that quantitatively incorporates fluid effects remains lacking. Here we combine theoretical analysis with dynamic rupture simulations to investigate how thermal pressurization, shearinduced dilatancy, and fault-normal fluid diffusion interact with rupture mechanics on finite-width faults. We derive closed-form expressions for strength evolution, fracture energy, and energy release rate, as inputs to the fundamental rupture-tip equation of motion. The numerical simulations agree with the theoretical rupture-tip equation of motion and thus provide a numerical validation. In addition, both theoretical and numerical models suggest a critical dilatancy that delineates two rupture modes: when dilatancy falls below this critical value, ruptures accelerate toward the limiting speed, whereas when dilatancy exceeds it, ruptures sustain steady slow propagation. Spatial variations in fault-zone hydraulic and mechanical properties can explain the observed slow-to-fast rupture transitions in subduction zones. By explicitly incorporating fault-fluid processes into the theoretical framework, our model reconciles a broad spectrum of rupture speeds and slow-to-fast transitions, with potential implications for seismic hazard assessment.

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