SCEC Award Number 25285 View PDF
Proposal Category Individual Research Project (Single Investigator / Institution)
Proposal Title Depth-dependent Evolution of Fault Zones and the Search for Informative Observables
Investigator(s)
Name Organization
Ahmed Elbanna University of Illinois at Urbana-Champaign
SCEC Milestones C3-1 SCEC Groups FARM, RC, Seismology
Report Due Date 03/15/2026 Date Report Submitted 05/07/2026
Project Abstract
 The dynamic interplay between earthquakes and fault zone structures has long been acknowledged as a critical mechanism in controlling source physics \citep{ben2008collective}, yet it remains an understudied topic due to the myriad of theoretical and computational challenges involved in such investigation. Active natural faults exist within broader damage zones characterized by a multitude of complex structural and geometric features, which are expected to affect earthquake nucleation, rupture propagation, potential for dilatation and compaction, energy partitioning between dissipation and radiation, and rupture arrest. Earthquakes, in turn, activate co-seismically off-fault damage that may be both distributed and localized, producing changes in fault zone geometry, elasticity, and rheology, which influence further energy radiation, post-seismic deformation, and subsequent earthquake sequences. These challenges suggest a need for a transformative approach to fill in these critical data gaps and to complement our expanding observational capabilities. Predictive physics-based numerical simulations for joint modeling of transient rheology, fault zone geometry, and seismicity, offer a promising pathway for addressing the aforementioned challenges. Here we will develop a prototype of such models to specifically investigate three major research questions: (a) How is the co-seismic off-fault damage distributed with depth along large strike-slip faults?, (b) How does the rate of healing contribute to further morphing of the fault zone structure during the interseismic period?, and (3) What observations are needed to better constrain fault zone structure at depth?.
SCEC Community Models Used Community Velocity Model (CVM)
Usage Description We use the community velocity model to define an approximate 1D velocity profile with depth for one of the problems considered in this research. We show that a layered velocity structure with a soft shallow layer may promote a flower like fault zone structure.
Intellectual Merit Understanding fault damage zone architecture requires resolving coupled, depth-dependent processes inaccessible to existing elastoplastic or 2D models. This work develops a 3D dynamic rupture simulator coupling continuum damage-breakage (CDB) rheology with slip-weakening friction, enabling spontaneous elastic-modulus evolution and granular transitions during rupture. Three physically distinct stress and pore-pressure configurations reveal that damage symmetry is governed by the pre-rupture strain invariant ratio, damage zone width is controlled by stress drop rather than frictional strength, and depth-dependent seismic properties produce flower-like structures matching field observations—all within a single unified framework.
Broader Impacts By reproducing asymmetric, symmetric, and en echelon damage patterns observed across fault systems worldwide, this framework bridges long-standing gaps between seismic tomography, field geology, and physics-based modeling. The open MOOSE-FARMS simulator provides a community resource for investigating fault zone evolution, ground motion amplification, and seismic hazard. Planned extensions to hydro-mechanical coupling, rate-and-state friction, and thermal effects will enable predictive modeling of fault zone recovery across the earthquake cycle—directly informing hazard assessments for active fault systems and training the next generation of computational earthquake scientists.
Project Participants USC and UIUC
Participants: Elbanna (UIUC/USC), Ben Zion (USC), and Chunhui Zhao (then a graduate student at UIUC, now a postdoctoral researcher at SCEC)
Exemplary Figure Figure 2
Linked Publications

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