Analysis and extension of earthquake rupture dynamics

Hayek Valencia, Jorge Nicolas (2025): Analysis and extension of earthquake rupture dynamics: a methodological exploration & links to global geodynamic studies. Dissertation, LMU München: Fakultät für Geowissenschaften

Abstract

Geophysics is a broad field that explains phenomenons on earth from an interdisciplinary and data rich perspective. One of its modern ramifications is earthquake rupture dynamics, in which the material properties and the stress field are collapsed onto a compact support in which maximum shear deformation localizes -or the fault plane is defined-, and its contextualization in the framework of friction brings a mechanical understanding of the energy budget throughout the fault, and thus of the dynamic propagation of the rupture. This nonlinear behaviour is reflected in the source characteristics that are identified, interpreted, and validated against observables, such as on-fault asperities, supershear occurrence, backward, bilateral and unilateral propagation, among others. This fundamentally data- and physics-driven approach faces particular challenges in constraining the initial conditions governing fault stresses and strengths, as it is highly sensitive to these parameters. This dissertation explores the extension of the initial conditions and assumptions used in rupture dynamic models through physics-driven methodologies. We first present a diffuse volumetric fault representation as an alternative to the traditional assumption of an infinitesimally thin fault representation. The study presents a 2D PETSc spectral element adaptation, se2dr, which adopts the stress glut method with a steady-state phase-field ansatz to reduce inherent spurious oscillations from the stress discontinuities inherent to the original stress glut method. The model successfully replicates planar interface results, while revealing dynamic complexities such as fault-oblique yielding within the volumetric fault zone. In a next step, we adopt a state-of-art dynamic rupture software SeisSol to investigate the dynamics of the 2021 Mw 7.4 Maduo earthquake. In this study we inform 3D dynamic rupture simulations, accounting for off-fault plasticity, with geodetically-inferred on-fault stress heterogeneities. The model can explain the event's complex kinematics and observations, in particular the mechanical viability of unilateral supershear propagation across this multi-segment fault system and its associated observational signatures. We further inform 3D dynamic rupture simulations, by coupling its initial conditions to the output of a long-term regional geodynamic model from pTatin3D. We develop a workflow to extract a fault geometry from the shear zone emergent from the evolving plastic strain in the long-term model. The study compares the effect of choices of the rheology and its associated stress, consistent with the fault geometry, on the dynamics of earthquake, the energy released, and its impact as an rupture arresting mechanism. The next part of this dissertation explores potential insights gained from a global geodynamic context, to understand large-scale deformation and the ambient stress field, thereby providing a contextual mechanical framework to regional studies. Following this line of thought, we extract maps of erosional/non-depositional periods, or hiatus, that serve as proxies for vertical surface deflections induce by mantle convection, or dynamic topography. This study highlights the temporal and spatial variation of such hiatus surfaces across continents, offering a test for mantle flow retrodictions and an observational tool to support the identification mantle flow regimes. Finally, we analyze the role of the mantle flow as a driver for the horizontal stress field from an analytical, Couette-Poisseuille flow representation of the asthenosphere. This study provides a process-driven explanation for global stress patterns observed in stress indicators compiled in the World Stress Map. It emphasizes the importance of considering a global domain in geodynamic studies, and carries implications on the expected asthenospheric stress magnitudes.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Keywords: Earthquake Physics, Earthquake rupture dynamics, Global Geodynamics, Numerical modelling and analysis, geophysics
• Themengebiete: 500 Naturwissenschaften und Mathematik ; 500 Naturwissenschaften und Mathematik > 550 Geowissenschaften
• Fakultäten: Fakultät für Geowissenschaften
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 19. Februar 2025
• 1. Bericht­erstatter:in: Bunge, Hans-Peter