On the rupture processes of large earthquakes using three-dimensional data-integrated dynamic rupture simulations

Ulrich, Thomas (2020): On the rupture processes of large earthquakes using three-dimensional data-integrated dynamic rupture simulations. Dissertation, LMU München: Fakultät für Geowissenschaften

Abstract

In this dissertation, I use 3D dynamic rupture modeling to understand the dynamics of previous large earthquakes and, more generally, to advance the physical understanding of coseismic processes on natural faults. I focus on a set of large and destructive earthquakes, characterized by puzzling features, and I conduct additional numerical analyses to investigate the scale-dependence of fault roughness effects. I first study the complex dynamics of the 2016 Mw 7.8 Kaikōura earthquake. I present a highly realistic 3D dynamic rupture scenario that reproduces key characteristics of the event and constrains puzzling features. I show that the observed rupture cascade is dynamically consistent with regional stress estimates and a crustal fault network geometry inferred from seismic and geodetic data. In the model, overpressurized fluids, low dynamic friction and stress concentrations induced by deep fault creep result in low apparent friction. I then present a coupled scenario of the 2018 Palu, Sulawesi earthquake and tsunami. The model, constrained by rapidly available observations, suggests that the primary tsunami source, a key riddle of the event, may have been direct earthquake-induced uplift and subsidence. This study demonstrates that physics-based interpretations can be an important part of the rapid earthquake response toolset. Next, I explore the dynamics of the 2004, Mw 9.1 - 9.3 Sumatra-Andaman earthquake. My models suggest that along-depth variation of trench sediments, off-fault plastic yielding, and along-arc variations of regional stresses and tectonic convergence rates are the dominant factors controlling the event's dynamics and kinematics. I demonstrate that 3D dynamic rupture modeling of megathrust earthquakes is now feasible and is critical for understanding the interplay of subduction mechanics, megathrust earthquakes and tsunami genesis. Finally, I investigate the scale-dependence of fault roughness effects on earthquake kinematics, dynamics and ground motion. The models on fractal strike-slip rough faults do not reveal systematic wavelength dependence of these effects. Nevertheless, the characteristic length scale posed by rupture process zone width affects rupture dynamics locally. In this study, I also propose strategies to capture fault roughness effects on coarser geometric fault representations, which offer an interesting compromise between computational efficiency and accuracy. Overall, this work advances the physical understanding of earthquake rupture processes. The developed models shed light on the physical mechanisms of cascading ruptures in complex fault systems and of megathrust earthquakes. In particular, they pose constraints on the conditions leading to such large earthquakes. This work contributes to advancing the current state-of-the-art of modeling earthquake source dynamics, by bridging the gap between rupture dynamic modeling and seismic observations.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Themengebiete: 500 Naturwissenschaften und Mathematik ; 500 Naturwissenschaften und Mathematik > 550 Geowissenschaften
• Fakultäten: Fakultät für Geowissenschaften
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 25. Mai 2020
• 1. Bericht­erstatter:in: Igel, Heiner