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Group A, Poster #161, Fault and Rupture Mechanics (FARM)

Absolute stress levels in models of low-heat faults: Links to seismological observables and differences for crack-like ruptures and self-healing pulses

Valere R. Lambert, & Nadia Lapusta
Poster Image: 

Poster Presentation

2022 SCEC Annual Meeting, Poster #161, SCEC Contribution #12476 VIEW PDF
Determining absolute stress levels on faults has profound implications for fault mechanics and earthquake physics. Recent studies have shown that fault shear stress can depend on the style of fault motion and spatial scale at which the stress is inferred, posing challenges for comparing notions of fault shear resistance from laboratory to field scales. Here we investigate measures of average fault shear stress and their relationship to seismologically inferable quantities using numerical simulations of earthquake sequences on rate-and-state faults with low heat production, due to chronic fluid overpressure and/or enhanced dynamic weakening from the thermal pressurization of pore fluids. We ...highlight that energy-based measures of average shear stress, which in our models are similar to the area-averaged shear stresses, can in principle be estimated from thermal constraints and seismic inferences of static stress drop and apparent stress. Our models demonstrate the significance of rapid dynamic weakening and healing of shear resistance during ruptures, as exhibited in self-healing pulses, for allowing faults to maintain higher average interseismic stress levels despite low dynamic resistance and realistic static stress drops, potentially explaining the difference between topography-based and heat-flow-based constraints on fault shear stress. Our results emphasize the distinction between dynamic versus static stress changes when relating earthquake source observations to absolute fault stress and suggest that re-examining estimates of radiated energy and static stress drop from large earthquakes may improve constraints on absolute stress levels on faults.