Seismic and Aseismic Fault Growth Lead to Different Fault Orientations

Preuss, Simon; Herrendörfer, Robert; Gerya, Taras; Ampuero, Jean‐Paul; Dinther, Ylona van

doi:10.1029/2019jb017324

Cited by 35 publications

(75 citation statements)

References 126 publications

(188 reference statements)

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“…The local friction coefficient evolves according to the invariant reformulation of rate-and state-dependent friction for a continuum, introduced by Herrendörfer et al (2018). This formalism was applied to freely and spontaneously growing seismic and aseismic faults by Preuss et al (2019), by interpreting how plastic deformation starts to localize and forms a shear band that approximates a fault zone of finite width that can host earthquakes. Localized bulk deformation and fault slip are related by defining the plastic slip…”

Section: Methodsmentioning

confidence: 99%

“…In this manuscript we develop a computational model that combines the following features: dynamic off-fault yielding in a visco-elasto-plastic material, long-term evolution of a geometrically complicated fault system, consistent simulation of multiple subsequent earthquakes on the same fault system, effect of the finite seismogenic-elastic depth. Our method builds upon and extends the recently developed STM-RSF numerical model for Seismo-Thermo-Mechanical modeling under Rateand-State Friction (van Dinther et al, 2013b;Herrendörfer et al, 2018;Preuss et al, 2019) to, for the first time, simulate cyclic seismic and aseismic fault growth. The STM model was developed in van Dinther et al (2013b, a) to bridge long geodynamic time scales of fault and lithosphere evolution with short time scales approximating earthquake sequences in a visco-elastoplastic medium.…”

Section: [D]mentioning

confidence: 99%

“…Herrendörfer et al (2018) developed the STM-RSF version to simulate sequences of earthquakes with time steps down to milliseconds using a new invariant rate-and-state friction (RSF) formulation on predefined, mature faults. Preuss et al (2019) extended the STM-RSF code to simulate aseismic and seismic fault growth. However, once a fault was formed and ruptured dynamically in a velocity-weakening bulk medium it continued to rupture indefinitely if unhindered by model boundaries.…”

Section: [D]mentioning

confidence: 99%

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Characteristics of earthquake ruptures and dynamic off-fault deformation on propagating faults

Dinther¹,

Preuss²,

Ampuero³

et al. 2020

Preprint

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Abstract. Natural fault networks are geometrically complex systems that evolve through time. The evolution of faults and their off-fault damage pattern are influenced by both dynamic earthquake ruptures and aseismic deformation in the interseismic period. To better understand each of their contributions to faulting we simulate both earthquake rupture dynamics and long-term deformation in a visco-elasto-plastic crust subjected to rate-and-state-dependent friction. The continuum mechanics-based numerical model presented here includes three new features. First, a 2.5-D approximation to incorporate effects of a viscoelastic lower crustal substrate below a finite depth. Second, we introduce a dynamically adaptive (slip-velocity-dependent) measure of fault width to ensure grid size convergence of fault angles for evolving faults. Third, fault localization is facilitated by plastic strain weakening of bulk rate-and-state friction parameters as inspired by laboratory experiments. This allows us to for the first time simulate sequences of episodic fault growth due to earthquakes and aseismic creep. Localized fault growth is simulated for four bulk rheologies ranging from persistent velocity-weakening to velocity-strengthening. Interestingly, in each of these bulk rheologies, faults predominantly localize and grow due to aseismic deformation. Yet, cyclic fault growth at more realistic growth rates is obtained for a bulk rheology that transitions from velocity-strengthening friction to velocity-weakening friction. Fault growth occurs under Riedel and conjugate angles and transitions towards wing cracks. Off-fault deformation, both distributed and localized, is typically formed during dynamic earthquake ruptures. Simulated off-fault deformation structures range from fan-shaped distributed deformation to localized Riedel splay faults. We observe that the fault-normal width of the outer damage zone saturates with increasing fault length due to the finite depth of the seismogenic zone. We also observe that dynamically and statically evolving stress fields from neighboring fault strands affect primary and secondary fault growth and thus that normal stress variations affect earthquake sequences. Finally, we find that the amount of off-fault deformation distinctly depends on the degree of optimality of a fault with respect to the prevailing but dynamically changing stress field. Typically, we simulate off-fault deformation on faults parallel to the loading direction. This produces a 6.5-fold higher off-fault energy dissipation than on an optimally oriented fault, which in turn has a 1.5-fold larger stress drop. The misalignment of the fault with respect to the static stress field thus facilitates off-fault deformation. These results imply that fault geometries bend, individual fault strands interact and that optimal orientations and off-fault deformation vary through space and time. With our work we establish the basis for simulations and analyses of complex evolving fault networks subject to both long-term and short-term dynamics.

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Section: Methodsmentioning

confidence: 99%

Section: [D]mentioning

confidence: 99%

Section: [D]mentioning

confidence: 99%

See 1 more Smart Citation

Characteristics of earthquake ruptures and dynamic off-fault deformation on propagating faults

Dinther¹,

Preuss²,

Ampuero³

et al. 2020

Preprint

Self Cite

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show abstract

“…Stress and/or strength variations due to, for example, variations in tectonic loading, stress changes from previous earthquakes, or local material heterogeneities, are expected, but poorly constrained, and therefore not included in this dynamic rupture model. Accounting for such features in relation to long term deformation can distinctly influence the stress field and lithological contrasts (e.g., van Dinther et al 2013;Dal Zilio et al 2018Preuss et al 2019;D'Acquisto et al 2018;van Zelst et al 2019). Realistic initial conditions in terms of stress and lithology are shown to significantly influence the dynamics of individual ruptures (Lotto et al 2017a;van Zelst et al 2019).…”

Section: The Sulawesi Earthquake Scenariomentioning

confidence: 99%

Coupled, Physics-Based Modeling Reveals Earthquake Displacements are Critical to the 2018 Palu, Sulawesi Tsunami

Ulrich

Vater

Madden

et al. 2019

Pure Appl. Geophys.

127

125

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The September 2018, M w 7.5 Sulawesi earthquake occurring on the Palu-Koro strike-slip fault system was followed by an unexpected localized tsunami. We show that direct earthquakeinduced uplift and subsidence could have sourced the observed tsunami within Palu Bay. To this end, we use a physics-based, coupled earthquake-tsunami modeling framework tightly constrained by observations. The model combines rupture dynamics, seismic wave propagation, tsunami propagation and inundation. The earthquake scenario, featuring sustained supershear rupture propagation, matches key observed earthquake characteristics, including the moment magnitude, rupture duration, fault plane solution, teleseismic waveforms and inferred horizontal ground displacements. The remote stress regime reflecting regional transtension applied in the model produces a combination of up to 6 m left-lateral slip and up to 2 m normal slip on the straight fault segment dipping 65 East beneath Palu Bay. The time-dependent, 3D seafloor displacements are translated into bathymetry perturbations with a mean vertical offset of 1.5 m across the submarine fault segment. This sources a tsunami with wave amplitudes and periods that match those measured at the Pantoloan wave gauge and inundation that reproduces observations from field surveys. We conclude that a source related to earthquake displacements is probable and that landsliding may not have been the primary source of the tsunami. These results have important implications for submarine strike-slip fault systems worldwide. Physics-based modeling offers rapid response specifically in tectonic settings that are currently underrepresented in operational tsunami hazard assessment.

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“…There is a need for development of computational algorithms that may nucleate and grow faults on the fly with minimum or no mesh dependency. Potential candidates include nonlocal damage and plasticity models ; Preuss et al (2019), extended finite element methods Borja (2009, 2013), and Discontinuous Galerkin scheme with adaptive mesh refinement Pelties et al (2012Pelties et al ( , 2014.…”

Section: Discussionmentioning

confidence: 99%

Dynamic rupture propagation on fault planes with explicit representation of short branches

Elbanna

2019

Earth and Planetary Science Letters

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An active fault zone is home to a plethora of complex structural and geometric features that are expected to affect earthquake rupture nucleation, propagation, and arrest, as well as interseismic deformation. Simulations of these complexities have been largely done using continuum plasticity or scalar damage theories. In this paper, we use a highly efficient novel hybrid finite element-spectral boundary integral equation scheme to investigate the dynamics of fault zones with small scale pre-existing branches as a first step towards explicit representation of anisotropic damage features in fault zones. The hybrid computational scheme enables exact near-field truncation of the elastodynamic field allowing us to use high resolution finite element discretization in a narrow region surrounding the fault zone that encompasses the small scale branches while remaining computationally efficient. Our results suggest that the small scale branches may influence the rupture in ways that may not be realizable in homogenized continuum models. Specifically, we show that these short secondary branches significantly affect the post event stress state on the main fault leading to strong heterogeneities in both normal and shear stresses and also contribute to the enhanced generation of high frequency radiation. The secondary branches also affect off-fault plastic strain distribution and suggest that co-seismic inelasticity is sensitive to pre-existing damage features. We discuss our results in the larger context of the need for modeling earthquake ruptures with high resolution fault zone physics.

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Seismic and Aseismic Fault Growth Lead to Different Fault Orientations

Cited by 35 publications

References 126 publications

Characteristics of earthquake ruptures and dynamic off-fault deformation on propagating faults

Characteristics of earthquake ruptures and dynamic off-fault deformation on propagating faults

Coupled, Physics-Based Modeling Reveals Earthquake Displacements are Critical to the 2018 Palu, Sulawesi Tsunami

Dynamic rupture propagation on fault planes with explicit representation of short branches

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