Reconciling Variability in Finite-Fault Models through Ensemble Dynamic Rupture Simulations: the Role of Stress Heterogeneity in the Tohoku-Oki Earthquake

Jeremy Wing Ching Wong, Alice-Agnes Gabriel, & Wenyuan Fan

Submitted September 7, 2025, SCEC Contribution #14509, 2025 SCEC Annual Meeting Poster #TBD

Finite-fault models provide detailed imaging of the spatio-temporal evolution of earthquakes, however, large variability among these slip models limits understanding of underlying dynamic rupture processes. The 2011 Mw 9.0 Tohoku-Oki earthquake, one of the largest and best recorded megathrust earthquakes, illustrates this challenge, with numerous finite-fault models proposing different slip distributions despite similar fits to observational data.

To address this issue, we develop ensembles of 3D dynamic rupture models as physics-based constraints, using Ensemble Kalman Inversion (EKI) and high-performance computing. We apply this approach to systematically evaluate the dynamic viability of 32 finite-fault models of the Tohoku-Oki earthquake. Our dynamic rupture models incorporate realistic fault geometry, 3D velocity structure, and fast-velocity weakening rate-and-state friction with depth-dependent frictional parameter a-b. We generate 26 spontaneously propagating, preferred dynamic rupture scenarios that balance regional tectonic stress with initial stress heterogeneity inferred from each slip model, requiring fewer than 12 forward simulations per case. Despite their variability, all preferred rupture scenarios reproduce the finite-fault slip distributions and match geodetic observations.

Interestingly, all dynamic rupture models produce large shallow slip toward the trench, resulting in only ~10% shallow slip deficit compared to the ~50% inferred from finite-fault models. We identify three dominant modes of dynamic rupture behavior: crack-like rupture, multiple rupture reactivation combining slip pulses and cracks, and simple pulse-to-crack transition. These rupture modes are controlled by the level of initial stress heterogeneity. Among these, multiple reactivation scenarios best match the frequency-dependent complexity observed during this earthquake. Our results suggest that the dynamic rupture of the Tohoku earthquake was controlled by the interplay between initial stress heterogeneity and dynamic restrengthening. Our EKI dynamic rupture modeling approach provides a new framework for efficiently assessing plausible rupture dynamics up to the largest earthquakes recorded to date and improving physics-based constraints on faulting conditions.

Citation
Wong, J., Gabriel, A., & Fan, W. (2025, 09). Reconciling Variability in Finite-Fault Models through Ensemble Dynamic Rupture Simulations: the Role of Stress Heterogeneity in the Tohoku-Oki Earthquake. Poster Presentation at 2025 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)