Amplified seismic radiation and delayed dynamic triggering: brittle rock damage as a catalyst for 3D cascading earthquake dynamics

Alice-Agnes Gabriel, Zihua Niu, Sebastian Wolf, Vladimir Lyakhovsky, Yehuda Ben-Zion, & Heiner Igel

Published September 8, 2024, SCEC Contribution #13970, 2024 SCEC Annual Meeting Poster #152

Understanding the nonlinear mechanical response of rocks and soils to seismic waves is crucial for accurate earthquake modeling, not only in sedimentary surface layers but also within fault zones where stress changes can exceed 10 MPa during earthquakes. However, traditional models often neglect the critical reduction in elastic moduli during fault rupture and seismic wave propagation, potentially ignoring important feedback mechanisms for earthquake dynamics and ground motion.

We use a novel 3D discontinuous Galerkin implementation of the nonlinear Continuum Damage Breakage Rheology Model (CDBRM) within the high-performance computing software SeisSol to investigate the effects of co-seismic moduli reduction in 3D dynamic rupture simulations. SeisSol is accessible through the Quakeworx Science Gateway.

Our findings reveal that the earthquake energy budget differs significantly between elastic and damage-inclusive scenarios. The effects of nonlinear off-fault damage include increased high-frequency seismic waves due to the rapid transition from solid to granular phases, slower rupture speeds, lower peak slip rates, and the formation of off-fault shear bands. The nonlinear seismic wave field exhibits frequency modulation, damage- and stress-induced anisotropy, and additional anelastic attenuation.

We uncover a new mechanism of delayed dynamic triggering driven by the interplay of damage-induced stress heterogeneity, rock moduli reduction, and co-seismic fault zone evolution in tensile step-over fault systems. Nonlinear damage facilitates rupture cascading across multi-fault systems, with varying delay times linked to differences in damage rheology and geometric fault zone evolution, suggesting potential for new observational constraints.

Our results highlight the importance of explicitly accounting for nonlinear co-seismic effects across source, path, and site to better understand 3D cascading rupture dynamics and their associated hazards.

Citation
Gabriel, A., Niu, Z., Wolf, S., Lyakhovsky, V., Ben-Zion, Y., & Igel, H. (2024, 09). Amplified seismic radiation and delayed dynamic triggering: brittle rock damage as a catalyst for 3D cascading earthquake dynamics. Poster Presentation at 2024 SCEC Annual Meeting.

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