Along‐Strike Variation and Migration of Long‐Term Slow Slip Events in the Western Nankai Subduction Zone, Japan

Takagi, Ryota; Uchida, Naoki; Obara, Kazushige

doi:10.1029/2018jb016738

Cited by 75 publications

(130 citation statements)

References 98 publications

(157 reference statements)

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“…Long stripe patterns of LFEs correspond to major ETS episodes. L-SSE means a long-term slow slip event in the Bungo Channel at the western edge of Shikoku island, which was detected by Takagi et al (2019). The vertical broken line corresponds to the timing of the 2011 Tohoku-Oki earthquake (Mw 9.0).…”

Section: Figurementioning

confidence: 99%

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: Figurementioning

confidence: 99%

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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“… 97 ) Although the amount of stress transferred from a given slow earthquake sequence is likely to be considerably small for triggering the rupture of a great earthquake, the frequent occurrence of slow earthquakes may result in stress accumulation, gradually approaching the critical rupture level. Takagi et al 43 ) revealed the northward migration of long-term SSEs along the subducting Philippine Sea plate, where the long-term SSEs migrated from the weakly coupled region in southeastern Kyushu to the firmly locked zone beneath Shikoku. Thus, a long-term SSE may load additional stress to the locked zone over a characteristic timescale of years.…”

Section: Discussionmentioning

confidence: 99%

“…Long-term SSEs were discovered in the Bungo Channel 1 ) and Tokai region 38 ) shortly after the deployment of GEONET in Japan. Long-term SSEs have since been detected at other locations, including the Kii Channel, 39 ) central Shikoku, 40 , 41 ) northern Miyazaki Prefecture, 42 , 43 ) and southern Miyazaki Prefecture. 44 ) These long-term SSEs are commonly observed between the locked and ETS zones along the subducting plate interface in southwest Japan.…”

Section: Classification Of Slow Earthquakesmentioning

confidence: 99%

“…Even though the geometry of the ETS source region differs, long-term SSEs frequently exhibit along-strike migration, as observed in the ETS activity, from southern Kyushu to central Shikoku. 43 ) The long-term SSE source regions are separated into four segments based on the distribution of the total slip amounts and recurrence interval, and a different slip amount can be observed along each segment. Further, a small slip was observed on the segment that is a downward extension of the coseismic rupture areas of the previous great earthquakes, whereas a large slip was observed on the segment that is a downward extension of the areas with no coseismic rupture.…”

Section: Characteristic Spatiotemporal Activity and Interaction Of Slmentioning

confidence: 99%

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Characteristic activities of slow earthquakes in Japan

Obara

2020

Proc. Jpn. Acad., Ser. B

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Slow earthquakes are a recently discovered phenomenon that mainly occur updip and downdip of the seismogenic zones of great earthquakes along the subducting plate interface. The spatiotemporal activity of various slow earthquakes occurring in the Nankai subduction zone is characterized by along-strike heterogeneity and along-dip systematic changes. Various slow earthquakes are horizontally distributed at their own depths and along-strike segments can be observed with respect to this distribution downdip of the locked zone; however, slow and great earthquakes occur in the same depth range near the Nankai Trough and Japan Trench axes. The frequently observed spatiotemporal interactions between different slow earthquakes can be attributed to their sensitivity and the stress transfer of the surrounding areas. This stress transfer is expected to extend to the adjacent sections in the seismogenic zone. Therefore, precise monitoring of slow earthquakes is important for future evaluations of great earthquakes, which requires the long-term maintenance and continuous improvement of the high-quality observation networks.

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“…However, slowslip events can be triggered by distant earthquakes (Araki 2017; Wallace et al 2017;Wei et al 2018), act like structural barriers (Vaca et al 2018;Rolandone 2018), or trigger other slow-slip events (Payero et al 2008;Kano et al 2019). Along-strike segmentation of slow-slip events in the Nankai Trough follows the spatial pattern of coupling in the seismogenic zone (Takagi et al 2019). Numerical simulations indicate that the recurrence pattern of slow slip is modulated by the earthquake cycle (Matsuzawa et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Structural control and system-level behavior of the seismic cycle at the Nankai Trough

Shi

Barbot

Wei

et al. 2020

Earth Planets Space

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The Nankai Trough in Southwest Japan exhibits a wide spectrum of fault slip, with long-term and short-term slowslip events, slow and fast earthquakes, all associated with different segments down the plate interface. Frictional and viscous properties vary depending on rock type, temperature, and pressure. However, what controls the downdip segmentation of the Nankai subduction zone megathrust and how the different domains of the subduction zone interact during the seismic cycle remains unclear. Here, we model a representative cross-section of the Nankai subduction zone offshore Shikoku Island where the frictional behavior is dictated by the structure and composition of the overriding plate. The intersections of the megathrust with the accretionary prism, arc crust, metamorphic belt, and upper mantle down to the asthenosphere constitute important domain boundaries that shape the characteristics of the seismic cycle. The mechanical interactions between neighboring fault segments and the impact from the long-term viscoelastic flow strongly modulate the recurrence pattern of earthquakes and slow-slip events. Afterslip penetrates down-dip and up-dip into slow-slip regions, leading to accelerated slow-slip cycles at depth and longlasting creep waves in the accretionary prism. The trench-ward migrating locking boundary near the bottom of the seismogenic zone progressively increases the size of long-term slow-slip events during the interseismic period. Fault dynamics is complex and potentially tsunami-genic in the accretionary region due to low friction, off-fault deformation, and coupling with the seismogenic zone.

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Along‐Strike Variation and Migration of Long‐Term Slow Slip Events in the Western Nankai Subduction Zone, Japan

Cited by 75 publications

References 98 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

Characteristic activities of slow earthquakes in Japan

Structural control and system-level behavior of the seismic cycle at the Nankai Trough

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