Coupling 3D geodynamics and dynamic earthquake rupture: fault geometry, rheology and stresses across timescales

TL;DR

This paper introduces a novel method that couples 3D geodynamic models with dynamic earthquake rupture simulations, enabling more realistic fault geometry and stress conditions to improve understanding of earthquake mechanics across timescales.

Contribution

It develops a new approach that integrates long-term geodynamics with dynamic rupture models, deriving fault geometry from lithospheric rheology and tectonic velocities without preset assumptions.

Findings

Long-term rheology influences fault slip behavior.

Minor stress variations can significantly affect rupture propagation.

Estimated critical slip distance falls within 0.6 to 1.5 meters.

Abstract

Tectonic deformation crucially 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 develop a new method that loosely couples 3D geodynamic models to 3D dynamic rupture simulations, 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 velocities using the medial axis transform. We perform three long-term geodynamics models of a strike-slip geodynamic system, each involving different continental crust rheology. We link these with nine dynamic rupture models, in which we investigate the role of varying fracture energy and plastic strain energy dissipation in the dynamic rupture behavior. These simulations suggest that for our fault, long-term rheology, and geodynamic system, a plausible critical linear slip weakening distance falls within Dc in [0.6,1.5]. Our results indicate that the long-term 3D stress field favors slip on fault segments better aligned with the regional plate motion and that 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.