The 2016 Mw 5.9 earthquake off the southeastern coast of Mie Prefecture as an indicator of preparatory processes of the next Nankai Trough megathrust earthquake

Hyodo, Mamoru; Nakanishi, Ayako; Yamashita, M; Hori, Takane; Kamiya, Shinichiro; Suzuki, Kensuke; Tonegawa, Takashi; Kodaira, Shuichi; Takahashi, Narumi; Kaneda, Yasufumi

doi:10.1186/s40645-018-0188-3

Cited by 22 publications

(17 citation statements)

References 61 publications

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“…A similar observation has been reported in Nankai, where shallow tremor and VLF earthquakes occurred after and close to an Mw 5.9 interplate earthquake (Annoura et al, ; Nakano, Hori, et al, ). Numerical simulation based on a laboratory‐driven friction law predicted afterslip in the region of tremor and VLF earthquakes (Nakano, Hyodo, et al, ). The association between triggered tremor and afterslip along the plate interface would also be an interesting topic for future work.…”

Section: Discussionmentioning

confidence: 99%

Shallow Low‐Frequency Tremor in the Northern Japan Trench Subduction Zone

Tanaka

Matsuzawa

Asano

2019

Geophysical Research Letters

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We found offshore shallow low‐frequency tremor in the northern Japan Trench subduction zone, using records from the Seafloor Observation Network for Earthquakes and Tsunamis along the Japan Trench. The tremor aligned with a narrow zone, which follows the 10‐ to 25‐km depth contours of the plate interface and occurred in two distinct areas, off Tokachi and Sanriku, separated by a gap. In the 1.75 years examined, two episodes lasting for a few weeks were identified off Tokachi. During these episodes, tremor occurred concurrently with swarms of very low frequency earthquakes and migrated laterally about 120 km along the trench strike. In contrast, tremor off Sanriku lasted shorter (half a day to 5 days) and repeated at shorter intervals (1–4 months). The variation in tremor behavior such as duration, recurrence, migration, and the association with very low frequency earthquakes suggests along‐strike heterogeneities in frictional properties at the shallow plate interface.

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Section: Discussionmentioning

confidence: 99%

Shallow Low‐Frequency Tremor in the Northern Japan Trench Subduction Zone

Tanaka

Matsuzawa

Asano

2019

Geophysical Research Letters

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“…Shallow VLFEs and tectonic tremors off Kii Peninsula, Japan. (a) Hypocentral locations of VLFEs reported by Nakano et al () and Nakano, Hori, et al (; blue and red circles), the earthquake off Mie and its aftershocks from Nakano, Hyodo, et al (; green circles), and intraslab earthquakes from the Japan Meteorological Agency catalog (gray). The red star in the inset indicates the epicenter of the 2016 Kumamoto earthquake.…”

Section: Datamentioning

confidence: 99%

“…Reported activity was concentrated in October 2015 and April 2016 (Figure b). The former period was spontaneous activity, whereas the latter appears to have been triggered by two moderate to large earthquakes (Figure a): an M W 5.9 offshore Mie Prefecture event on 1 April 2016 (Nakano, Hyodo, et al, ) and the M W 7.0 Kumamoto mainshock of 16 April 2016 (K. Asano & Iwata, ). The former occurred on the plate interface of the Nankai subduction zone around node E of DONET1 (Figure a), while the latter was a crustal earthquake on Kyushu Island, Japan (~500 km from the source region of shallow slow earthquakes).…”

Section: Datamentioning

confidence: 99%

Scaled Energy Estimation for Shallow Slow Earthquakes

Yabe

Tonegawa

2019

JGR Solid Earth

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Deep and shallow slow earthquakes occur at the edge of the seismogenic zone in the Nankai subduction zone. Deep slow earthquakes occur under high‐temperature and high‐pressure conditions, whereas shallow slow earthquakes occur at lower temperatures and pressures. Although these two types of slow earthquake show qualitatively similar behaviors, such as slow deformation and depleted high‐frequency seismic signals, their similarities have not yet been evaluated in quantitative ways. In this work, we analyze shallow tectonic tremors accompanied by very low frequency earthquakes off Kii Peninsula, Japan. We estimate the seismic energy of the shallow tectonic tremors by correcting for the site amplifications of ocean bottom seismic stations and seismic attenuation in the shallow accretionary prism. The estimated seismic energy rates of these tectonic tremors are compared with seismic moment rates of accompanying very low frequency earthquakes, revealing that the scaled energy of shallow slow earthquakes is roughly constant, ~10−9 to 10−8, which is 0 to 1 order of magnitude larger than the typical scaled energy of deep slow earthquakes.

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“…The 2016 Mw 5.8 event, however, which occurred on April 1 11:39 local time, about 85 km closer to land than the 2004 event ( Fig. 1), has been suggested to be a plate boundary event (e.g., Wallace et al 2016;Nakano et al 2018;Takemura et al 2018). The 2016 Mw 5.8 event is the largest plate boundary event that occurred in the source region of the 1944 Tonankai earthquake (Mw ~ 8) after its occurrence (Kikuchi et al 2003;Asano 2018).…”

Section: Introductionmentioning

confidence: 98%

“…The 2016 Mw 5.8 event is the largest plate boundary event that occurred in the source region of the 1944 Tonankai earthquake (Mw ~ 8) after its occurrence (Kikuchi et al 2003;Asano 2018). That the 2016 Mw 5.8 event occurred in the coseismic slip area of the Tonankai earthquake has been interpreted to be an indicator of the ongoing process preparing for the next megathrust earthquake in the Nankai Trough (Nakano et al 2018). The ground motions for this event were recorded by hundreds of strong-motion stations on land and some tens of ocean bottom seismographs (Kawaguchi et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Evidence of strong long-period ground motions of engineering importance for Nankai Trough plate boundary earthquakes: comparison of ground motions of two moderate-magnitude earthquakes

Dhakal

Suzuki

Kimura

et al. 2018

Earth Planets Space

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We analyzed strong-motion and broadband recordings of two moderate-magnitude earthquakes that occurred in the Nankai Trough. The first event was the 2004 Mw 6.5 southeast off-Kii peninsula earthquake, an aftershock event inside the Philippine Sea Plate near the Nankai Trough axis. The second event was the 2016 Mw 5.8 southeast off-Mie Prefecture earthquake, an independent event in the rupture area of the 1944 Mw ~ 8 Tonankai earthquake. The centroid depths were 11 and 14 km for the 2004 and 2016 events, respectively. Despite a large difference in the moment magnitude between the two events, the JMA magnitude (Mj) was 6.5 for both the events. We found that the short-period ground motions (e.g., response spectra at periods < 1 s) as well as the much longer-period ground motions (> 20 s) for the 2016 event scaled generally well with the moment magnitude of the event. In contrast, the ground motions from the 2016 event were comparable to those for the larger-moment-magnitude 2004 event at equal distances at periods of about 2-20 s in wide areas and the observed acceleration response spectra at those periods were noticeably underestimated for the 2016 event by the ground motion prediction equation (GMPE) that employs Mw. An examination of the existing subsurface velocity model suggested that the difference in the relative location of the two events with respect to the thick accretionary prism of low seismic velocity most probably caused the comparable amplitude of the seismic waves at those periods. As a result, we posit that the values of Mj are equal for the two events because Mj is estimated using the displacement amplitude of ground motions at periods smaller than about 6 s. On the other hand, GMPE employing Mj generally described the observed data well. The results suggested that the plate boundary earthquakes in the Nankai Trough may excite strong long-period ground motions of engineering importance, and these ground motions appear to be better explained by Mj than by Mw in GMPEs for moderate-magnitude earthquakes in the Nankai Trough subduction zone. which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

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The 2016 Mw 5.9 earthquake off the southeastern coast of Mie Prefecture as an indicator of preparatory processes of the next Nankai Trough megathrust earthquake

Cited by 22 publications

References 61 publications

Shallow Low‐Frequency Tremor in the Northern Japan Trench Subduction Zone

Shallow Low‐Frequency Tremor in the Northern Japan Trench Subduction Zone

Scaled Energy Estimation for Shallow Slow Earthquakes

Evidence of strong long-period ground motions of engineering importance for Nankai Trough plate boundary earthquakes: comparison of ground motions of two moderate-magnitude earthquakes

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