Event Size Distribution of Shallow Tectonic Tremor in the Nankai Trough

Yabe, Suguru; Sugioka, Hiroko; Shinohara, Masanao; Ide, Satoshi

doi:10.1029/2019gl083029

Cited by 28 publications

(22 citation statements)

References 42 publications

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“…LFEs are small seismic events contained within tremor, first recognized by Katsumata & Kamaya [ 83 ] in southwest Japan. They represent barely observable seismic signals extracted from continuous waveform data, which are characterized by lower frequencies (more than 1 Hz) and longer durations (0.2–0.5 s) than those observed for ordinary microearthquakes [ 84 , 85 ]. It is possible that localized, near-source attenuation of seismic waves, which may be the result of high pore-fluid pressures and rock damage in the LVL, could cause the bandlimited nature of LFEs through the depletion of high frequencies [ 86 , 87 ].…”

Section: Geophysical Observations Of Sst Environment and Sourcementioning

confidence: 99%

What’s down there? The structures, materials and environment of deep-seated slow slip and tremor

Behr

Bürgmann

2021

Phil. Trans. R. Soc. A.

123

151

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Deep-seated slow slip and tremor (SST), including slow slip events, episodic tremor and slip, and low-frequency earthquakes, occur downdip of the seismogenic zone of numerous subduction megathrusts and plate boundary strike-slip faults. These events represent a fascinating and perplexing mode of fault failure that has greatly broadened our view of earthquake dynamics. In this contribution, we review constraints on SST deformation processes from both geophysical observations of active subduction zones and geological observations of exhumed field analogues. We first provide an overview of what has been learned about the environment, kinematics and dynamics of SST from geodetic and seismologic data. We then describe the materials, deformation mechanisms, and metamorphic and fluid pressure conditions that characterize exhumed rocks from SST source depths. Both the geophysical and geological records strongly suggest the importance of a fluid-rich and high fluid pressure habitat for the SST source region. Additionally, transient deformation features preserved in the rock record, involving combined frictional-viscous shear in regions of mixed lithology and near-lithostatic fluid pressures, may scale with the tremor component of SST. While several open questions remain, it is clear that improved constraints on the materials, environment, structure, and conditions of the plate interface from geophysical imaging and geologic observations will enhance model representations of the boundary conditions and geometry of the SST deformation process. This article is part of a discussion meeting issue ‘Understanding earthquakes using the geological record’.

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Section: Geophysical Observations Of Sst Environment and Sourcementioning

confidence: 99%

What’s down there? The structures, materials and environment of deep-seated slow slip and tremor

Behr

Bürgmann

2021

Phil. Trans. R. Soc. A.

123

151

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“…We referred to the seismic energy catalog of Nakano et al. (2019) for the 2016 off‐Kumano activity, and for this study we estimated the radiated seismic energy of tremor events during the 2018 off‐Kii Channel activity.…”

Section: Observed Changes Of Tremor Size Distributionsmentioning

confidence: 99%

“…A recent study of shallow tectonic tremor along the Nankai trough (Nakano et al., 2019) found that the event size distribution follows a tapered Gutenberg‐Richter (TGR) distribution (Kagan, 2002), given by

Φ (M) = {(M_{t} / M)}^{β} exp (\frac{M_{t} - M}{M_{c}}) f o r M_{t} < M < \infty,

where M is seismic moment, M t is the catalog completeness threshold, and M c is the corner moment.

β

controls the slope of the distribution;

β = 2 b / 3

in the ordinary Gutenberg‐Richter law.…”

Section: Introductionmentioning

confidence: 99%

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Changes of Event Size Distribution During Episodes of Shallow Tectonic Tremor, Nankai Trough

Yabe

2021

Geophysical Research Letters

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Slow earthquakes follow a power‐law size distribution with an exponential taper for the largest events. We investigated changes in the size distribution of shallow tectonic tremor events during two prolonged tremor episodes (>1 month) along the Nankai trough and found that the slope of the size distributions increased while the cut‐off magnitudes decreased late during each episode, as tremor activity waned. Interpreting these changes with the two‐dimensional probabilistic cell automaton model of slow earthquakes, we found that a decrease in event ignition probability or an increase in energy dissipation during slip can qualitatively explain the observed changes. These changes imply that a decrease in accumulated stress or pore‐fluid pressure on the fault interface occurred during each tremor episode. Because the tremor source migrates during an episode, the changes in the size distribution parameters can be attributed to spatial variations or temporal changes in the source characteristics.

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“…Exponential distributions have also been reported for the size‐frequency (Hiramatsu et al., 2008) and size‐energy rate distributions of tremor events (Yabe & Ide, 2014). However, power‐law distributions with and without an exponential taper were observed in the size‐frequency distributions of shallow tremors in the Nankai Trough (Nakano et al., 2019) and LFEs in Cascadia (Bostock et al., 2015), respectively. These features are well explained by statistical models of slow earthquakes; for example, a Brownian model reproduces well the exponential scaling of duration‐amplitude distributions (Ide, 2008) and the power‐law scaling with an exponential taper of cumulative size distributions (Ide & Yabe, 2019).…”

Section: Introductionmentioning

confidence: 99%

Variations in the Characteristic Amplitude of Tectonic Tremor Induced by Long‐Term Slow Slip Events

et al. 2021

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Recent discoveries of slow earthquakes have revealed the diversity of slip phenomena and subduction dynamics worldwide. Slow earthquakes are usually classified into long-term slow slip events (L-SSEs, durations of months to years; e.g., Ozawa et al., 2002), short-term slow slip events (S-SSEs, durations of days to weeks; e.g., Dragert et al., 2001), very-low-frequency (VLF) earthquakes (e.g., Ito et al., 2007), low-frequency earthquakes (LFEs; e.g., Katsumata & Kamiya, 2003), and tectonic tremor (e.g., Obara, 2002). Slow earthquakes show characteristic scaling relationships that separate them from regular earthquakes. For example, Ide et al. (2007) proposed that the seismic moment of a slow earthquake is proportional to its duration, although the seismic moments of SSEs in Cascadia (Michel et al., 2019) and LFEs in Shikoku, Japan (Supino et al., 2020), are reported to be proportional to the cube of their duration, as observed for regular earthquakes. The duration-amplitude distribution of tremor events obeys an exponential distribution rather than a power-law distribution as usually observed for regular earthquakes (Watanabe et al., 2007

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Event Size Distribution of Shallow Tectonic Tremor in the Nankai Trough

Cited by 28 publications

References 42 publications

What’s down there? The structures, materials and environment of deep-seated slow slip and tremor

What’s down there? The structures, materials and environment of deep-seated slow slip and tremor

Changes of Event Size Distribution During Episodes of Shallow Tectonic Tremor, Nankai Trough

Variations in the Characteristic Amplitude of Tectonic Tremor Induced by Long‐Term Slow Slip Events

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