Longer Migration and Spontaneous Decay of Aseismic Slip Pulse Caused by Fault Roughness

Ozawa, Shinobu; Hatano, Takahiro; Kame, Nobuki

doi:10.1029/2018gl081465

Cited by 21 publications

(17 citation statements)

References 48 publications

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“…One simple idea would be to incorporate the pre-stress that, in some statistical sense, is expected from repeated multiple cycles on a rough fault; however, that is not sufficient. The results reported here suggests that roughness drag (Fang and Dunham, 2013) explains key characteristics of earthquake ruptures on rough faults (see also Tal et al, 2018;Ozawa et al, 2019). Importing the correct stress distribution to a planar fault will not describe the influence of roughness drag.…”

Section: A Planar Fault Approximationmentioning

confidence: 73%

“…Other models have been developed that simulate the whole seismic cycle (Tal et al, 2018;Tal and Hager, 2018a;Ozawa et al, 2019). However, these methods lack a mechanism for stress relaxation, such as off-fault plasticity, and are purely elastic.…”

Section: Introductionmentioning

confidence: 99%

“…The spatial extent of the slip patch must be much larger than λ min for this to be valid. Roughness drag can be generalized to self-affine faults (Ozawa et al, 2019), but here I focus on the strictly self-similar case. In Section 3.1.1, I will use roughness drag to understand the certain rupture characteristic of the simulations in a quantitative manner.…”

Section: Introductionmentioning

confidence: 99%

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Crack to pulse transition and magnitude statistics during earthquake cycles on a self-similar rough fault

Heimisson

2020

Earth and Planetary Science Letters

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Faults in nature demonstrate fluctuations from planarity at most length scales that are relevant for earthquake dynamics. These fluctuations may influence all stages of the seismic cycle; earthquake nucleation, propagation, arrest, and inter-seismic behavior. Here I show quasi-dynamic plane-strain simulations of earthquake cycles on a self-similar and finite 10 km long rough fault with amplitude-to-wavelength ratio α = 0.01. The minimum roughness wavelength, λ min , and nucleation length scales are well resolved and much smaller than the fault length. Stress relaxation and fault loading is implemented using a variation of the backslip approach, which allows for efficient simulations of multiple cycles without stresses becoming unrealistically large. I explore varying λ min for the same stochastically generated realization of a rough fractal fault. Decreasing λ min causes the minimum and maximum earthquakes sizes to decrease. Thus the fault seismicity is characterized by smaller and more numerous earthquakes, on the other hand, increasing the λ min results in fewer and larger events. However, in all cases, the inferred b-value is constant and the same as for a reference no-roughness simulation (α = 0). I identify a new mechanism for generating pulse-like ruptures. Seismic events are initially crack-like, but at a critical length scale, they continue to propagate as pulses, locking in an approximately fixed amount of slip. I investigate this transition using simple arguments and derive a characteristic pulse length, L c = λ min /(4π 4 α 2) and slip distance, δ c based on roughness drag. I hypothesize that the ratio λ min /α 2 can be roughly estimated from kinematic rupture models. Furthermore, I suggest that when the fault size is much larger than L c , then most space-time characteristics of slip differ between a rough fault and a corresponding planar fault.

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Section: A Planar Fault Approximationmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Crack to pulse transition and magnitude statistics during earthquake cycles on a self-similar rough fault

Heimisson

2020

Earth and Planetary Science Letters

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“…On rate‐and‐state fault segments with velocity‐weakening friction, SSEs occur when the slipping region is large enough to cause slip acceleration, as during earthquake nucleation, but too small for that slip event to reach seismic slip rates (Liu & Rice, 2005). Several variants of rate‐and‐state fault models can significantly extend the range of parameters suitable for SSEs, including changes from velocity‐weakening to velocity‐strengthening friction with increasing slip rates (Leeman et al, 2016; Shibazaki & Shimamoto, 2007), geometric complexities and roughness (Li & Liu, 2016; Ozawa et al, 2019; Romanet et al, 2018), and decreases in pore fluid pressure due to shear‐induced dilatancy (Marone et al, 1990; Segall & Rice, 1995; Segall et al, 2010). SSEs can also be obtained in models of rate‐and‐state faults with velocity‐strengthening friction and additional destabilizing effects, for example, poroelastic (Heimisson et al, 2019), and in models with viscoplastic bulk effects (Tong & Lavier, 2018).…”

Section: Introductionmentioning

confidence: 99%

Unraveling Scaling Properties of Slow‐Slip Events

Zilio

Lapusta

Avouac

2020

Geophysical Research Letters

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A major debate in geophysics is whether earthquakes and slow-slip events (SSEs) arise from similar failure mechanisms. Recent observations from different subduction zones suggest that SSEs follow the same moment-duration scaling as earthquakes, unlike qualitatively different scaling proposed by earlier studies. Here, we examine the scaling properties using dynamic simulations of frictional sliding. The resulting sequences of SSEs match observations from the Cascadia subduction zone, including the earthquake-like cubic moment-duration scaling. In contrast to conventional and widely used assumptions of magnitude-invariant rupture velocities and stress drops, both simulated and natural SSEs have rupture velocities and stress drops that increase with event magnitudes. These findings support the same frictional origin for both earthquakes and SSEs while suggesting a new explanation for the observed SSEs scaling.Plain Language Summary Tectonic faults produce a wide spectrum of slip modes, ranging from fast earthquakes to slow-slip events. Whether slow-slip events and regular earthquakes result from a similar physics is debated. Here we present numerical simulations to show that slow-slip events can result from frictional sliding like seismic slip, with an additional mechanism that prevents acceleration to fast slip due to the presence of fluids. The model succeeds in reproducing a realistic sequence of slow-slip events and provides an excellent match to the observations from the Cascadia subduction zone, including the observation that the moment, which quantifies the energy released by fault slip, is proportional to the cube of the duration. Importantly, our study demonstrates that this scaling arises for different reasons from the traditional explanation proposed for regular earthquakes.

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“…On a rough fault, local stresses are perturbed during rupture growth, leading to complex rupture behavior. Manifestations of this complexity include rapid accelerations and decelerations of the rupture front, slip heterogeneity (Chester & Chester 2000;Dieterich & Smith 2009;Dunham et al 2011b;Shi & Day 2013), resistance to slip (Dieterich & Smith 2009;Fang & Dunham 2013), supershear transitions (Bruhat et al 2016), variability in moment release (Zielke et al 2017), in nucleation processes (Harbord et al 2017;Ozawa et al 2019), and inelastic deformation (Hirakawa & Ma 2018).…”

mentioning

confidence: 99%

Influence of fault roughness on surface displacement: from numerical simulations to coseismic slip distributions

Bruhat¹,

Klinger²,

Vallage³

et al. 2019

Preprint

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Field studies characterized early on natural faults as rough, i.e. non-planar at all scales. Fault roughness induces local stress perturbations, which dramatically affect rupture behavior, resulting in slip heterogeneity. The relation between fault roughness and produced slip remains, however, a key knowledge gap in current numerical and field studies. In this study, we analyze numerical simulations of earthquake rupture to determine how roughness influences final slip profiles. Using a rupture catalog of thousands dynamic rupture simulations on non-planar fault profiles with varying roughness and background shear stress levels, we demonstrate that fault roughness affects the spectral characteristics of the resulting slip distribution. In particular, slip distributions become increasingly more self-affine, i.e. containing more short wavelength at smaller scale, with higher fault roughness, despite self-similar initial fault profiles. We also show that, at very short wavelength (<1km), the fractal dimension of the slip distributions dramatically changes with increasing roughness, background shear stress, and rupture behavior (e.g., sub-Rayleigh vs. supershear). The existence of a critical wavelength around 1km, under which more short wavelength are either preserved or created, suggests the role of rupture process and dynamic effects, together with fault geometry, in resulting slip distributions. The same spectral analysis is finally performed on high-resolution coseismic slip distributions from real strike-slip earthquakes. Compared to numerical simulations, all events present slip distributions that are much more self-affine than the profiles from numerical simulations. A different critical wavelength, here around 5-6km, appears, potentially informing about a critical asperity length. While we show here that the relation between fault roughness and produced slip distribution is much more complex than expected, this study is a first attempt at using statistical analyses of numerical simulations on rough faults to investigate observed coseismic slip distributions.

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Longer Migration and Spontaneous Decay of Aseismic Slip Pulse Caused by Fault Roughness

Cited by 21 publications

References 48 publications

Crack to pulse transition and magnitude statistics during earthquake cycles on a self-similar rough fault

Crack to pulse transition and magnitude statistics during earthquake cycles on a self-similar rough fault

Unraveling Scaling Properties of Slow‐Slip Events

Influence of fault roughness on surface displacement: from numerical simulations to coseismic slip distributions

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