Coupling 3D Geodynamics and Dynamic Rupture: Rheology and Stress Control on Strike-Slip Fault Evolution and Earthquake Dynamics

Abstract

Tectonic deformation shapes the Earth's surface, with strain localization resulting in the formation of shear zones and faults that accommodate significant tectonic displacement. Earthquake dynamic rupture models, which provide valuable insights into earthquake mechanics and seismic ground motions, rely on initial conditions such as pre-stress states and fault geometry. However, these are often inadequately constrained due to observational limitations. To address these challenges, we loosely couple 3D geodynamic models to 3D strike-slip dynamic rupture simulations, for the first time accounting for off-fault plastic deformation, providing a mechanically consistent framework for earthquake analysis. Our approach does not prescribe fault geometry but derives it from the underlying lithospheric rheology and tectonic evolution of the system, captured by long-term geodynamic modeling. We perform three long-term geodynamics models of a strike-slip system, each involving different continental crust rheology. We link these with 14 dynamic rupture models, in which we investigate the role of varying fracture energy and plastic strain energy dissipation in the dynamic rupture behavior. Our results highlight the important role of the brittle-ductile transition and indicate that the long-term 3D stress field, which is directly related to the rheology of the lithosphere, favors slip on fault segments better aligned with the regional plate motion. Fault bends and minor variations in the long-term 3D stress field can strongly affect rupture dynamics, providing a physical mechanism for arresting earthquake propagation. Our geodynamically informed earthquake models highlight the need for detailed 3D fault modeling across time scales for a comprehensive understanding of earthquake mechanics.