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Abstract Using a novel high‐performance computing implementation of a nonlinear continuum damage‐breakage model, we explore interactions between 3D co‐seismic off‐fault damage, seismic radiation, and rupture dynamics. Our simulations demonstrate that off‐fault damage enhances high‐frequency wave radiation above 1 Hz, reduces rupture speed and alters the total kinetic energy. We identify distinct damage regimes separated by solid‐granular transition, with smooth distributions under low damage conditions transitioning to localized, mesh‐independent shear bands upon reaching brittle failure. The shear band orientations depend systematically on the background stress and agree with analytical predictions. The brittle damage inhibits transitions to supershear rupture propagation and the rupture front strain field results in locally reduced damage accumulation during supershear transition. The dynamically generated damage yields uniform and isotropic ratios of fault‐normal to fault‐parallel high‐frequency ground motions. Co‐seismic damage zones exhibit depth‐dependent width variations, becoming broader near the Earth's surface consistent with field observations, even under uniform stress conditions. We discover a new delayed dynamic triggering mechanism in multi‐fault systems, driven by reductions in elastic moduli and the ensuing stress heterogeneities in 3D tensile fault step‐overs. This mechanism affects the static and dynamic stress fields and includes the formation of high shear‐traction fronts around localized damage zones. The brittle damage facilitates rupture cascading across faults, linking delay times directly to damage rheology and fault zone evolution. Our results help explain near‐fault high‐frequency isotropic radiation and delayed rupture triggering, improving our understanding of earthquake processes, seismic wavefields and fault system interactions.
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A phase‐field model for quasi‐dynamic nucleation, growth, and propagation of rate‐and‐state faults
Abstract Despite its critical role in the study of earthquake processes, numerical simulation of the entire stages of fault rupture remains a formidable task. The main challenges in simulating a fault rupture process include the complex evolution of fault geometry, frictional contact, and off‐fault damage over a wide range of spatial and temporal scales. Here, we develop a phase‐field model for quasi‐dynamic fault nucleation, growth, and propagation, which features two standout advantages: (i) it does not require any sophisticated algorithms to represent fault geometry and its evolution; and (ii) it allows for modeling fault nucleation, propagation, and off‐fault damage processes with a single formulation. Built on a recently developed phase‐field framework for shear fractures with frictional contact, the proposed formulation incorporates rate‐ and state‐dependent friction, radiation damping, and their impacts on fault mechanics and off‐fault damage. We show that the numerical results of the phase‐field model are consistent with those obtained from well‐verified approaches that model the fault as a surface of discontinuity, without suffering from the mesh convergence issue in the existing continuous approaches to fault rupture (e.g., the stress glut method). Further, through numerical examples of fault propagation in various settings, we demonstrate that the phase‐field approach may open new opportunities for investigating complex earthquake processes that have remained overly challenging for the existing numerical methods.
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- PAR ID:
- 10390435
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- International Journal for Numerical and Analytical Methods in Geomechanics
- Volume:
- 47
- Issue:
- 2
- ISSN:
- 0363-9061
- Page Range / eLocation ID:
- p. 187-211
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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