SCEC2022 Plenary Talk, Fault and Rupture Mechanics (FARM)

Advancing models of earthquake source processes towards physics-informed seismic hazard assessment

Valere R. Lambert

Oral Presentation

2022 SCEC Annual Meeting, SCEC Contribution #12557
Numerical models of earthquake source processes are continuously advancing to incorporate new physical factors - including fault geometry and roughness, shear heating and fluid effects, visco-plastic deformation, and off-fault damage/healing - in order to identify and quantify the relative importance of different physical ingredients for short and long-term fault behavior. The expansion in modeling capabilities has been accompanied by community efforts to compare and verify simulation codes for dynamic rupture and sequences of earthquakes and aseismic slip (SEAS). Such initiatives have achieved excellent agreement among different codes for a growing collection of benchmarks. The continued development of robust modeling practices builds further confidence in numerical earthquake models as valuable tools for community efforts to bridge insight between laboratory and field observations for models of fault stress and fault zone rheology; calibrate observational techniques for estimating source properties and explore their relation to rupture/fault physics; and make predictions that can in principle be validated through lab or field studies.

The growing capability of simulating larger-scale, longer-term sequences of earthquakes with wider distributions of rupture sizes has illuminated increasingly complex fault behavior in even seemingly simple physical models. While simulations have shown that some statistical distributions of simulated quantities, such as scaling relations between average rupture properties like static stress drop and seismic moment, may be reliably determined from well-formulated numerical models, other quantities, such as the probability of an earthquake rupture jumping from one fault to another, can exhibit acute sensitivity to choices in numerical parameterization and physical assumptions. The extreme sensitivity of some hazard parameters in numerical studies to small perturbations may also suggest that such measures would be highly sensitive to physical perturbations on natural faults, implying that such hazard parameters could be highly unstable and impractical to estimate in a reliable manner. These developments pose intriguing questions about parameterizations of hazard and motivate further study of the sensitivity of hazard parameters to modeling ingredients, as well as metrics for describing seismic and aseismic rupture sequences and their connection to fault/bulk physics, tasks for which physics-based modeling is well-suited.