Tidal modulation and back‐propagating fronts in slow slip events simulated with a velocity‐weakening to velocity‐strengthening friction law

Hawthorne, J. C.; Rubin, Allan M.

doi:10.1002/jgrb.50107

Cited by 35 publications

(89 citation statements)

References 78 publications

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“…Rubin 2011) or with a transition from velocity-weakening to velocity-strengthening at increasing slip rate (e.g. Hawthorne and Rubin 2013a;Shibazaki and Iio 2003). Some of these mechanisms require tuning model parameters within a very narrow range of values, which is problematic.…”

Section: Generation Of Slow Slip Eventsmentioning

confidence: 99%

“…Figure 7 shows the steady-state friction coefficient, µ(V, D c /V), as a function of slip velocity, for different values of V 2 . The VW-VS transition is governed by V 2 and friction properties a and b: it occurs at V t = V 2 b−a a (Hawthorne and Rubin 2013a). Strengthening effectively sets a soft limit to the maximum slip rate.…”

Section: Generation Of Slow Slip Eventsmentioning

confidence: 99%

“…Fault size and plate loading rate are also well constrained. Here we build up on a comprehensive study by Hawthorne and Rubin (2013a) that identified model parameters that reproduce observed SSE properties. The value of D c spans a relatively wide range in laboratory results and contributes to stress drop, but its effect trades off with b and σ.…”

Section: Generation Of Slow Slip Eventsmentioning

confidence: 99%

“…The range is especially narrow with the "slip law", the state evolution law that is most consistent with laboratory experiments with large velocity steps. This fine tuning issue has motivated the study of other physical ingredients to explain the generation of SSE, including more sophisticated friction laws with transitions from velocity-weakening to velocity-strengthening at increasing slip rate (Hawthorne and Rubin 2013a) and the hardening effect of fault gouge dilatancy in fluid-saturated fault zones (Segall et al 2010). Here we will investigate if fault heterogeneity can lead to robust SSEs under classical rate-and-state friction with the slip law.…”

Section: What Do Tremor Migration Patterns Tell Us About Fault Rheology?mentioning

confidence: 99%

“…Slow-slip events (SSEs) and non-volcanic tremors (NVTs) discovered in the last decade (Rogers and Dragert 2003) have greatly expanded the spectrum of observed earthquake behavior (Beroza and Ide 2011;Hawthorne and Rubin 2010;Ide et al 2007a;Peng and Gomberg 2010). SSEs are aseismic slip transients with a small slip rate (few orders of magnitude larger than the plate loading rate, well below seismic slip rate), they evolve more slowly and have a much longer duration than regular earthquakes, and have been mostly observed near the deep seismic-aseismic transition (30 to 50 km) below the conventional seismogenic zone depth.…”

Section: Introductionmentioning

confidence: 99%

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Preprint: Tremor migration patterns and the collective behavior of deep asperities mediated by creep

Luo¹,

Ampuero²

2017

Preprint

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Slow-slip events (SSE) and non-volcanic tremors have revealed a broad spectrum of earthquake behavior, involving entangled seismic and aseismic slip, and offer a unique window into fault mechanics at the bottom of seismogenic zones. A hierarchy of migration patterns of tremors has been observed in the Cascadia subduction zone, including large-scale along-strike tremor propagation and Rapid Tremor Reversals (RTR) migrating in opposite directions with much higher propagation speeds. Here we show that these tremor migration patterns can be reproduced by two end-member models of a fault with heterogeneous mechanical properties, composed of competent asperities embedded in a more frictionally stable, incompetent matrix. In the SSE-driven-tremor model, SSEs are spontaneously generated by the matrix, even in absence of seismic asperities, and drive tremor. In the tremor-driven-SSE model the matrix is stable, it slips steadily in absence of asperities, and SSEs result from the collective behavior of tremor asperities interacting via transient creep in the form of local afterslip fronts. We study these two end-member models through 2D quasi-dynamic multi-cycle simulations of faults governed by rate-and-state friction with heterogeneous frictional properties and effective normal stress, using the earthquake simulation software QDYN . In both models, tremor migration patterns emerge from interactions between asperities mediated by creep transients. The models successfully reproduce forward tremor propagation and RTRs, as well as various other observed tremor migration patterns, without the need to finely tune model parameters. Our modeling results suggest that, in contrast to a common view, SSE could be a result of tremor activity. Also, the hierarchical pattern of tremor migrations provides general constraints on fault zone rheology, and the location of RTRs and other tremor patterns might shed light on the finer scale spatial variability of fault properties. We also find that, despite important interactions between asperities, tremor activity rates are proportional to the underlying aseismic slip rate, supporting an approach to estimate SSE properties with high spatial-temporal resolutions via tremor activity.

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Section: Generation Of Slow Slip Eventsmentioning

confidence: 99%

Section: Generation Of Slow Slip Eventsmentioning

confidence: 99%

Section: Generation Of Slow Slip Eventsmentioning

confidence: 99%

Section: What Do Tremor Migration Patterns Tell Us About Fault Rheology?mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Preprint: Tremor migration patterns and the collective behavior of deep asperities mediated by creep

Luo¹,

Ampuero²

2017

Preprint

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Imaging slow slip fronts in Cascadia with high precision cross‐station tremor locations

Rubin

Armbruster

2013

Geochem Geophys Geosyst

140

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[1] We apply a new method to obtain accurate locations of tremor sources beneath southern Vancouver Island. Unlike more standard ''cross-time'' methods, which compare waveforms from different time windows at the same station, this ''cross-station'' method compares waveforms from the same time window at widely separated stations. It performs well, relative to cross-time methods, when the response to an impulsive tremor source is dominated by the main arrival rather than coda and when multiple colocated sources are active within the time window examined. We focus on a region roughly 10 km across that was monitored by the POLARIS deployment from 2003 to 2006. Relative location errors appear to be <1 km, allowing us to image in great detail rapid and small-scale tremor migrations that arise behind the main slow slip front. The secondary fronts tend to (a) start at or within about 1 km of the main tremor front, and propagate back along strike at rates of 10-20 km/h; (b) less commonly do the reverse, ending at the main front; or (c) propagate up or downdip at or within 1-2 km of the main front. Estimated stress drops in the secondary events are comparable to that in the main event, implying that their 25-50 times greater propagation speed results from a similarly greater slip speed.

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Inferring fault rheology from low‐frequency earthquakes on the San Andreas

et al. 2013

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[1] Families of recurring low-frequency earthquakes (LFEs) within nonvolcanic tremor (NVT) on the San Andreas fault in central California show strong sensitivity to shear stress induced by the daily tidal cycle. LFEs occur at all levels of the tidal shear stress and are in phase with the very small,~400 Pa, stress amplitude. To quantitatively explain the correlation, we use a model from the existing literature that assumes the LFE sources are small, persistent regions that repeatedly fail during shear of a much larger scale, otherwise aseismically creeping fault zone. The LFE source patches see tectonic loading, creep of the surrounding fault which may be modulated by the tidal stress, and direct tidal loading. If the patches are small relative to the surrounding creeping fault then the stressing is dominated by fault creep, and if patch failure occurs at a threshold stress, then the resulting seismicity rate is proportional to the fault creep rate or fault zone strain rate. Using the seismicity rate as a proxy for strain rate and the tidal shear stress, we fit the data with possible fault rheologies that produce creep in laboratory experiments at temperatures of 400 to 600°C appropriate for the LFE source depth. The rheological properties of rock-forming minerals for dislocation creep and dislocation glide are not consistent with the observed fault creep because strong correlation between small stress perturbations and strain rate requires perturbation on the order of the ambient stress. The observed tidal modulation restricts ambient stress to be at most a few kilopascal, much lower than rock strength. A purely rate dependent friction is consistent with the observations only if the product of the friction rate dependence and effective normal stress is~0.5 kPa. Extrapolating the friction rate strengthening dependence of phyllosilicates (talc) to depth would require the effective normal stress to be~50 kPa, implying pore pressure is lithostatic. If the LFE source is on the order of tens of meters, as required by the model, rate-weakening friction rate dependence (e.g., olivine) at 400 to 600°C requires that the minimum effective pressure at the LFE source is~2.5 MPa.

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Tidal modulation and back‐propagating fronts in slow slip events simulated with a velocity‐weakening to velocity‐strengthening friction law

Cited by 35 publications

References 78 publications

Preprint: Tremor migration patterns and the collective behavior of deep asperities mediated by creep

Preprint: Tremor migration patterns and the collective behavior of deep asperities mediated by creep

Imaging slow slip fronts in Cascadia with high precision cross‐station tremor locations

Inferring fault rheology from low‐frequency earthquakes on the San Andreas

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