Temporal variation in seismic moment release rate of slow slips inferred from deep low-frequency tremors in the Nankai subduction zone

Kono, Yoko; Nakamoto, Keita; Hiramatsu, Yoshihiro

doi:10.1186/s40623-020-1142-3

Cited by 5 publications

(6 citation statements)

References 28 publications

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“…The occurrence rate remained similar, regardless of stress perturbations induced by the megathrust rupture. This observation is consistent with Kono et al (2020), who demonstrated that there were no temporal variations in the estimated rate of seismic moment release by tectonic tremor along the Nankai subduction zone as a result of the Tohoku-Oki earthquake. But, note that the spatio-temporal evolution of LFEs has changed from ~2012, in Shikoku island where major ETS episodes more frequently migrated long-distance through multiple segments than before the Tohoku-Oki earthquake.…”

Section: Methodssupporting

confidence: 91%

Detection of deep low-frequency earthquakes in the Nankai subduction zone over 11 years using a matched filter technique

Kato¹,

Nakagawa²

2020

Preprint

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To improve our understanding of the long-term behavior of low-frequency earthquakes (LFEs) along the tremor belt of the Nankai subduction zone, we applied a matched filter technique to continuous seismic data recorded by a dense and highly sensitive seismic network over an 11 year window, April 2004 to August 2015. We detected a total of ~510,000 LFEs, or ~23× the number of LFEs in the JMA catalog for the same period. During long-term slow slip events (SSEs) in the Bungo Channel, a series of migrating LFE bursts intermittently occurred along the fault-strike direction, with slow hypocenter propagation. Elastic energy released by long-term SSEs appears to control the extent of LFE activity. We identify slowly migrating fronts of LFEs during major episodic tremor and slip (ETS) events, which extend over distances of up to 100 km and follow diffusion-like patterns of spatial evolution with a diffusion coefficient of ~10 4 m 2 /s. This migration pattern closely matches the spatio-temporal evolution of tectonic tremors reported by previous studies. At shorter distances, up to 15 km, we discovered rapid diffusion-like migration of LFEs with a coefficient of ~10 5 m 2 /s. We also recognize that rapid migration of LFEs occurred intermittently in many streaks during major ETS episodes. These observations suggest that slow slip transients contain a multitude of smaller, temporally clustered fault slip events whose evolution is controlled by a diffusional process.

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Section: Methodssupporting

confidence: 91%

Detection of deep low-frequency earthquakes in the Nankai subduction zone over 11 years using a matched filter technique

Kato¹,

Nakagawa²

2020

Preprint

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“…Before 2011, migrations of tremor episodes in western Shikoku terminated at a particular area that corresponds to the segment boundary between A and B in this study (Figures 5 and 6), but in some later episodes tremor activities migrated farther to the east crossing the segment boundary (Takagi et al, 2016). On the other hand, Kono et al (2020) reported that seismic moment rate inferred from apparent moment of tremors in Shikoku did not change around 2011. Taking these two observations into consideration, a probable scenario is that long‐term slip rate in the ETS zone does not change largely as in Segment A (Figure 8), but the occurrence of a long‐term SSE in the gap zone induces a synchronization of the timing of slip occurrence on the adjacent segments, and then the resultant slip extent and the seismic moment of a connected short‐term SSE becomes larger.…”

Section: Discussionmentioning

confidence: 97%

Slip Distributions of Short‐Term Slow Slip Events in Shikoku, Southwest Japan, From 2001 to 2019 Based on Tilt Change Measurements

Hirose

Kimura

2020

JGR Solid Earth

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In the southwest Japan subduction zone, short-term slow slip events (SSEs) accompanying nonvolcanic tremor (ETS: episodic tremor and slip) occur repeatedly with recurrence intervals of several months. It is important to know the detailed slip areas of the SSEs because short-term SSEs occur at the downdip extension of a megathrust earthquake rupture zone, and hence, the SSEs play a key role in the stress buildup processes of the megathrust earthquakes. Although most of the previous studies model a SSE fault motion with uniform slip on a rectangular fault, this may lead to a bias in estimating the slip area. In this study we estimate a spatial slip distribution for each of the short-term SSEs from tilt offset measurements. In total, the slip distributions of 61 SSEs in Shikoku from January 2001 to March 2019 are obtained. The ETS zone in Shikoku is divided into three segments in terms of slip history of the SSEs. Before 2011, the slip areas of most of the SSEs are limited in any one of the three segments. After 2012, however, the number of SSEs having a slip area that extends to multiple segments increases. The slip histories at each position in the ETS zone suggest that the short-term SSE activity is affected by the occurrence of nearby long-term SSEs. The average slip rate over 18 years suggests that an estimated slip deficit in the ETS zone in western Shikoku could be released by long-term SSEs, or coseismic slip or afterslip of the megathrust earthquakes.

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“…and therefore the source dimensions are also very large. Moreover, the relationship between M0 and x' is quasi-linear and tends to infinity as shown in literature [11,29,71].…”

Section: Workmentioning

confidence: 89%

A New Approach For Physically-Based Probabilistic Seismic Hazard Analysis For Portugal

Zacchei¹,

Brasil²

2021

Preprint

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Probabilistic seismic hazard analysis (PSHA) is nowadays the more complete analysis method to estimate the seismic input for structural analysis. However, it is strongly influenced by seismogenic parameters and attenuation equations. Here PSHA using empirical Green’s functions (EGFs) with 2 + 2 variables is carried out, which are correlated through the moment magnitude. This combination, already known as “physically-based PSHA (pb-PSHA)”, is an original approach that should be disseminated because it provides a good alternative in countries where the seismogenic zones and attenuation equations are not well known. The proposed model is based on linear faults, random, periodic, impulsive, linear source functions, and a punctual hypocentre. Differential equations are explained. Results are shown in terms of new seismic parameters, specific return periods and ground accelerations. The studied country is Portugal. It appears to the authors that no study has been published about pb-PSHA for Portugal.

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Temporal variation in seismic moment release rate of slow slips inferred from deep low-frequency tremors in the Nankai subduction zone

Cited by 5 publications

References 28 publications

Detection of deep low-frequency earthquakes in the Nankai subduction zone over 11 years using a matched filter technique

Detection of deep low-frequency earthquakes in the Nankai subduction zone over 11 years using a matched filter technique

Slip Distributions of Short‐Term Slow Slip Events in Shikoku, Southwest Japan, From 2001 to 2019 Based on Tilt Change Measurements

A New Approach For Physically-Based Probabilistic Seismic Hazard Analysis For Portugal

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