Connecting slow earthquakes to huge earthquakes

Obara, Kazushige; Kato, Aitaro

doi:10.1126/science.aaf1512

Cited by 531 publications

(552 citation statements)

References 55 publications

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“…(e.g. Obara and Kato 2016;Yamashita et al 2015) Furthermore, it is not a viable candidate mechanism for depth-dependent slip behavior on strike-slip faults.…”

Section: Discussionmentioning

confidence: 99%

Stability of faults with heterogeneous friction properties and effective normal stress

2018

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Abundant geological, seismological and experimental evidence of the heterogeneous structure of natural faults motivates the theoretical and computational study of the mechanical behavior of heterogeneous frictional interfaces. Fault zones are composed of a mixture of materials with contrasting strength, which may affect the spatial variability of seismic coupling, the location of high-frequency radiation and the diversity of slip behavior observed in natural faults. To develop a quantitative understanding of the effect of strength heterogeneity on the mechanical behavior of faults, here we investigate a fault model with spatially variable frictional properties and pore pressure. Conceptually, this model may correspond to two rough surfaces in contact along discrete asperities, the space in between being filled by compressed gouge. The asperities have different permeability than the gouge matrix and may be hydraulically sealed, resulting in different pore pressure. We consider faults governed by rate-and-state friction, with mixtures of velocity-weakening and velocity-strengthening materials and contrasts of effective normal stress. We systematically study the diversity of slip behaviors generated by this model through multi-cycle simulations and linear stability analysis. The fault can be either stable without spontaneous slip transients, or unstable with spontaneous rupture. When the fault is unstable, slip can rupture either part or the entire fault. In some cases the fault alternates between these behaviors throughout multiple cycles. We determine how the fault behavior is controlled by the proportion of velocity-weakening and velocity-strengthening materials, their relative strength and other frictional properties. We also develop, through heuristic approximations, closed-form equations to predict the stability of slip on heterogeneous faults. Our study shows that a fault model with heterogeneous materials and pore pressure contrasts is a viable framework to reproduce the full spectrum of fault behaviors observed in natural faults: from fast earthquakes, to slow transients, to stable sliding. In particular, this model constitutes a building block for models of episodic tremor and slow slip events.Keywords: fault heterogeneity; heterogeneous pore-pressure; slip instability; earthquakes; rate-and-state friction; linear stability analysis Highlights:1. A comprehensive study of slip behaviors in fault models with mixed velocity-strengthening / velocity-weakening materials and heterogeneous effective normal stress 2. Fault stability investigated with numerical rate-and-state simulations and analytical linear stability analysis 3. Rich range of slip behaviors including steady-slip, slow aseismic slip transients, ruptures localized in part of the fault (P-instability), ruptures breaking the whole fault (T-instability) and combinations of both 4. Closed form equations that accurately describe the stability conditions for P-instabilities and T-instabilities 5. A useful framework to understand the full spectru...

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“…(e.g. Obara and Kato 2016;Yamashita et al 2015) Furthermore, it is not a viable candidate mechanism for depth-dependent slip behavior on strike-slip faults.…”

Section: Discussionmentioning

confidence: 99%

Stability of faults with heterogeneous friction properties and effective normal stress

2018

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“…Because of limited in situ monitoring combined with lower detection thresholds, geodetic data are less commonly used to study earthquake precursors. Therefore, the link between foreshock activity and associated deformation transients has never been directly established for periods exceeding a few weeks, although it has been observed and suggested [Obara and Kato, 2016, and references therein].…”

Section: Introductionmentioning

confidence: 99%

An 8 month slow slip event triggers progressive nucleation of the 2014 Chile megathrust

Socquet

Valdes

Jara

et al. 2017

Geophysical Research Letters

170

142

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The mechanisms leading to large earthquakes are poorly understood and documented. Here we characterize the long‐term precursory phase of the 1 April 2014 Mw8.1 North Chile megathrust. We show that a group of coastal GPS stations accelerated westward 8 months before the main shock, corresponding to a Mw6.5 slow slip event on the subduction interface, 80% of which was aseismic. Concurrent interface foreshocks underwent a diminution of their radiation at high frequency, as shown by the temporal evolution of Fourier spectra and residuals with respect to ground motions predicted by recent subduction models. Such ground motions change suggests that in response to the slow sliding of the subduction interface, seismic ruptures are progressively becoming smoother and/or slower. The gradual propagation of seismic ruptures beyond seismic asperities into surrounding metastable areas could explain these observations and might be the precursory mechanism eventually leading to the main shock.

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“…Geodetic and seismological observations have detected slow earthquakes in the circum-Pacific subduction zones since the late 1990s (Obara and Kato 2016). Slow earthquakes have different characteristic space-time scales, and a scaling law holds between their moment magnitudes (M w ) and durations (Ide et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Two long-term slow slip events around Tokyo Bay found by GNSS observation during 1996–2011

Tanaka

Yabe

2017

Earth Planets Space

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Slow slip events (SSEs) with durations ranging from days to more than a decade have been observed in plate subduction zones around the world. In the Kanto district in Japan, several SSEs have been identified based on geodetic observations. However, none of these events have had durations largely exceeding a year. In this study, we show that long-term SSEs with durations longer than 3 years occurred before the year 2000 and after 2007 on the upper interface of the Philippine Sea Plate at depths of 30-40 km. The fault model determined by inversion of global navigation satellite system data is located northeast of Tokyo Bay, where a seismic gap and low seismic wave velocities were detected by seismological observations. Moreover, the acceleration periods of the fault slip corresponded well with increases in the background seismicity for shallower earthquakes. The slip history was also temporally correlated with the long-term shear stress changes governed mainly by non-tidal variations in the ocean bottom pressure. However, the predicted slip from the long-term stress change was too small to reproduce the observed slow slips. To prove the causal relationship between the SSEs and the external stress change, more advanced modeling is necessary to confirm whether such a small slip can trigger an SSE.

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Connecting slow earthquakes to huge earthquakes

Cited by 531 publications

References 55 publications

Stability of faults with heterogeneous friction properties and effective normal stress

Stability of faults with heterogeneous friction properties and effective normal stress

An 8 month slow slip event triggers progressive nucleation of the 2014 Chile megathrust

Two long-term slow slip events around Tokyo Bay found by GNSS observation during 1996–2011

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