Long-term slow slip events along the Nankai trough subduction zone after the 2011 Tohoku earthquake in Japan

Ozawa, Shinzaburo

doi:10.1186/s40623-017-0640-4

Cited by 46 publications

(88 citation statements)

References 28 publications

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“…1). In the Bungo Channel, most of these long-term SSEs were nearly of equal magnitudes (Ozawa et al 2013;Kobayashi and Yamamoto 2011), although smaller ones have also occurred (Ozawa 2017). In the Tokai region, the duration of the 2000-2005 longterm SSE (Suito and Ozawa 2009) was longer than those of earlier events detected by tide gauge and tiltmeter data (Kobayashi and Yoshida 2004;Yamamoto et al 2005).…”

Section: Introductionmentioning

confidence: 87%

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Objective detection of long-term slow slip events along the Nankai Trough using GNSS data (1996–2016)

Kobayashi¹

2017

Earth Planets Space

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This paper presents a method for objective detection of long-term slow slip events with durations on the order of years, on the plate boundary along the Nankai Trough, relying on global navigation satellite system daily coordinate data. The Chugoku region of Japan was held fixed to remove common mode errors, and a displacement component was calculated relative to the direction of plate subduction. Correlations were then calculated between this displacement component and a 3-year ramp function with a 1-year slope. Nearly all periods of strong correlation coincide with periods of previously reported long-term slow slip events. A period of strong correlation around the Kii Channel in 2000-2002 is attributed to a previously undocumented long-term slow slip event beneath the Kii Channel and the eastern part of Shikoku Island with an equivalent moment magnitude of 6.6. This detection method reveals variation among long-term slow slip events along the Nankai Trough.

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Section: Introductionmentioning

confidence: 87%

“…6). In addition, small long-term SSEs in western Shikoku in 2005 (Kobayashi 2010;Takagi et al 2016) and in the Bungo Channel in 2014 (Ozawa 2017) appear in the figure. Takagi et al (2016) also reported a small long-term SSE in western Shikoku in 2011-2013.…”

Section: Spatiotemporal Distribution Of Displacementsmentioning

confidence: 99%

Objective detection of long-term slow slip events along the Nankai Trough using GNSS data (1996–2016)

Kobayashi¹

2017

Earth Planets Space

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“…We initially fix the slip duration at T = 300 days for long‐term SSE detection. This duration is a typical timescale for long‐term SSEs within the study area (Ozawa, ; Yarai & Ozawa, ). Since the SSE displacement signals have simple shapes without oscillations, the detection is not so sensitive to the assumed duration of the ramp function.…”

Section: Methodsmentioning

confidence: 99%

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

2019

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We detected 24 long-term slow slip events (SSEs) in the western Nankai subduction zone, Japan, from 1996 to 2017 using a newly developed method: grid-based determination of slow slip events (GriD-SSEs). GriD-SSE systematically detects long-term SSEs and determines their fault parameters by fitting modeled displacement time series to observed Global Navigation Satellite System data. The detected SSEs included 11 previously undocumented events. The results suggest an along-strike segmentation of long-term SSEs. The along-strike variations in SSE recurrence intervals and total slip amounts appear to correlate with the variation of updip interplate locking. Long-term SSEs are less frequent in the downdip extensions of the Nankai megathrust (M W 8-9) and Hyuga-nada earthquakes (M W 7.5), with~6-year recurrence intervals and total slip amounts that account for only 10-20% of the plate convergence. However, long-term SSEs do occur frequently downdip of the Hyuga-nada stable sliding zone and of the gap between the Nankai and Hyuga-nada earthquakes, with 2-to 3-year recurrence intervals and total slip amounts that account for 50-60% of the plate convergence. This correlation suggests that the long-term SSE activity is controlled by the updip locked areas owing to the stress shadowing effect. We also observed that the long-term SSEs repeatedly migrated in the downdip regions from the southwestern creeping zone to the northeastern Nankai megathrust locked zone. This SSE migration may represent the current state of stress accumulation and release processes that are controlled by the along-strike variations in interplate coupling along the entire western Nankai subduction zone.

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“…This reflects the fact that the magnitude or spatial extension of the long‐term SSE in 2010 ( M w 7.0) was larger than that in 2014 ( M w 6.2) (Ozawa, ). The aseismic slip rate during the long‐term SSE in 2010 (Figure 10d of Ozawa et al, ) is larger than in 2014 (Figure 4c of Ozawa, ). Consequently, the stress change by long‐term SSE in 2010 can be larger than in 2014.…”

Section: Discussionmentioning

confidence: 99%

“…The time length of a graph is 2 years. The horizontal black arrows show periods of long‐term SSEs in 2010 and 2014 (Ozawa, ). The areas surrounded by the polygons correspond to G1 (black) and G2 (blue), the same as in Figure .…”

Section: Discussionmentioning

confidence: 99%

Temporal Activity Modulation of Deep Very Low Frequency Earthquakes in Shikoku, Southwest Japan

Baba

Takeo

Obara

et al. 2018

Geophysical Research Letters

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We investigated long‐term changes in the activity of deep very low frequency earthquakes (VLFEs) in western Shikoku, southwest part of the Nankai subduction zone in Japan for 13 years by the matched‐filter technique. VLFE activity is expected to be a proxy of interplate slips. In the Bungo channel, where long‐term slow slip events (SSEs) occurred frequently, the cumulative number of detected VLFEs increased rapidly in 2010 and 2014, which were modulated by long‐term SSEs. In the neighboring inland region near the Bungo channel, the cumulative number increased steeply every 6 months. This stepwise change was accompanied by episodic tremors and slips. Deep VLFE activity in western Shikoku has been low since the latter half of 2014. This decade‐scale quiescence may be attributed to the change in interplate coupling strength in the Nankai subduction zone.

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Long-term slow slip events along the Nankai trough subduction zone after the 2011 Tohoku earthquake in Japan

Cited by 46 publications

References 28 publications

Objective detection of long-term slow slip events along the Nankai Trough using GNSS data (1996–2016)

Objective detection of long-term slow slip events along the Nankai Trough using GNSS data (1996–2016)

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

Temporal Activity Modulation of Deep Very Low Frequency Earthquakes in Shikoku, Southwest Japan

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