[S-CG40] Science of slow-to-fast earthquakes

[SCG40-26] Fault valving and fluid-pressure cycling in slow and fast earthquakes

★Invited Papers

*Luca Dal Zilio¹ (1.Earth Observatory of Singapore, Nanyang Technological University, Singapore)

Keywords:Earthquake Physics, Solid-Fluid Interactions, Poroelasticity, Slow and Fast Earthquakes

Traditional models of the earthquake cycle often neglect the dynamic interplay between fluid pressure variations and poroelastic effects in fault mechanics, despite increasing evidence of solid-fluid interactions influencing fault mechanics and the spectrum of slow-to-fast slip phenomena. In this study we introduce an advanced Hydro-Mechanical Earthquake Cycles (H-MECs) framework that encapsulates the interaction between solid and fluid phases within faults, thereby enriching our understanding of poroelastic stresses and fluid dynamics in fault systems. Our developed 2-D antiplane strike-slip fault model is embedded within a poro-visco-elasto-plastic compressible medium and is governed by rate- and state-dependent friction laws, enhanced with a novel permeability evolution mechanism that reflects the impact of fault slip variations and sealing over time. By simulating fluid migration in the seismogenic zone and considering the effects of metamorphic reactions as potential sources of fluids, our model probes into the scales of critical nucleation sizes. This allows an assessment of the interplay between fault friction, poroelastic stresses, and solid-fluid interactions. Our results reveal that for larger nucleation sizes, the solid-fluid interplay and poroelastic effects significantly influence fault behavior, with substantial seismic activities increasing fault permeability and promoting the migration of pressurized fluids. This process triggers slow-slip phenomena within the seismogenic zone. Conversely, for smaller nucleation sizes, the synergy between fault friction and solid-fluid interactions facilitates the emergence of seismic swarms through the fault valving mechanism, characterized by the successive occurrence of minor quakes followed by the pore pressure-driven migration of fluids. This research underscores the key role of transient fluid effects and poroelastic responses in modulating the spectrum of slip behaviors on faults, elucidating the conditions under which slow and fast slips occur. Moreover, it shines a light on the driving forces behind seismic swarm propagation via fault valving. By integrating hydro-mechanical insights with interdisciplinary methodologies, including advanced computational techniques and data-driven analysis, our study contributes to the comprehension of the complex dynamics governing slow-to-fast earthquake transitions.