Subduction zone paleoseismology along the Pacific coast of northeast Japan — progress and remaining problems

Sawai, Yuki

doi:10.1016/j.earscirev.2020.103261

Cited by 35 publications

(30 citation statements)

References 115 publications

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“…It has also been noted that the slip characteristics of this earthquake were similar to those of the 2011 Tohoku-Oki earthquake, which may have led to an 9M-class earthquake with a large slip in the shallow part of the plate interface (Ioki and Tanioka, 2016). In fact, traces of 15 tsunami deposits that span the past 6,000 years have been found (Sawai, 2020), and given the interval between the event of the Seventeenth century and the preceding event (some point in the 12th or 13th century), and the interval since the previous event, the indications are that a similar largest-class tsunami is imminent (Cabinet Office, 2020b). Furthermore, from the crustal deformation data on the land area, it is estimated that the slip-deficit that corresponds with the past source area is expanding (Hashimoto et al, 2012), and a seismic gap off the coast of Nemuro with low microseismic activity was noted by Takahashi and Kasahara (2013).…”

Section: Problem Settingsupporting

confidence: 52%

Sensitivity Analysis for Seafloor Geodetic Constraints on Coseismic Slip and Interseismic Slip-Deficit Distributions

et al. 2021

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Estimating the coseismic slip distribution and interseismic slip-deficit distribution play an important role in understanding the mechanism of massive earthquakes and predicting the resulting damage. It is useful to observe the crustal deformation not only in the land area, but also directly above the seismogenic zone. Therefore, improvements in terms of measurement precision and increase in the number of observation points have been proposed in various forms of seafloor observation. However, there is lack of research on the quantitative evaluation of the estimation accuracy in cases where new crustal deformation observation points are available or when the precision of the observation methods have been improved. On the other hand, the crustal structure models are improving and finite element analysis using these highly detailed crustal structure models is becoming possible. As such, there is the real possibility of performing an inverted slip estimation with high accuracy via numerical experiments. In view of this, in this study, we proposed a method for quantitatively evaluating the improvement in the estimation accuracy of the coseismic slip distribution and the interseismic slip-deficit distribution in cases where new crustal deformation observation points are available or where the precision of the observation methods have been improved. As a demonstration, a quantitative evaluation was performed using an actual crustal structure model and observation point arrangement. For the target area, we selected the Kuril Trench off Tokachi and Nemuro, where M9-class earthquakes have been known to occur in the past and where the next imminent earthquake is anticipated. To appropriately handle the effects of the topography and plate boundary geometry, a highly detailed three-dimensional finite element model was constructed and Green’s functions of crustal deformation were calculated with high accuracy. By performing many inversions via optimization using Green’s functions, we statistically evaluated the effect of increase in the number of observation points of the seafloor crustal deformation measurement and the influence of measurement error, taking into consideration the diversity of measurement errors. As a result, it was demonstrated that the observation of seafloor crustal deformation near the trench axis plays an extremely important role in the estimation performance.

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Section: Problem Settingsupporting

confidence: 52%

Sensitivity Analysis for Seafloor Geodetic Constraints on Coseismic Slip and Interseismic Slip-Deficit Distributions

et al. 2021

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“…However, the CT images and ITRAX pro les did not provide useful information to assess whether or not the event deposits had been eroded. Regarding the lack of historical documents and su cient quantitative estimation of inundation processes and sources (e.g., Sawai 2017Sawai , 2020, the question remains whether or not the BC 500-400…”

Section: Paleotsunami History Along the Southern And Central Part Of mentioning

confidence: 99%

“…Tsunami deposits are useful for identifying tsunami events with more extended time scales, i.e., more than hundreds of years. Therefore, they are effective for detecting huge tsunami events with prolonged recurrence intervals (Goto et al 2020;Sawai 2012Sawai , 2020Sugawara et al 2012). Due to the Tohoku earthquake and tsunami in 2011, considerable effort (by scienti c communities) has been dedicated to elucidating paleo-tsunami events using tsunami deposits.…”

Section: Introductionmentioning

confidence: 99%

Three thousand year paleo-tsunami history of the southern part of the Japan Trench

Higaki

Goto

Yanagisawa

et al. 2020

Preprint

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This study conducted a field survey and multiproxy analyses on sediment cores retrieved from the Kobatake-ike pond in Choshi City, Chiba prefecture, Japan. Kobatake-ike pond is located at a high elevation (i.e., 11 m above present-day sea level) and faces the southern part of the Japan Trench. Three sedimentological events were detected within the continuous mud and peat sequences of three thousand years. Based on the multi-proxy analyses, including mineralogical composition, diatom assemblages, and geochemical markers, these sedimentological events were associated with past tsunamis. The most recent event was a sandy layer from the AD 1677 Enpo tsunami, reported by an earlier study conducted in the pond. The estimated recurrence interval for tsunamis was approximately 700 years, comparable to that of the central part of the Japan Trench. The timing of at least two of three sedimentological events seems to have been close (i.e., intervals of few tens of years) before or after the occurrence of large earthquakes and tsunamis along the central part of the Japan Trench. This implies a possible spatiotemporal relation of earthquake generations between the central and southern parts of the Japan Trench, which can be associated with drastic changes in stress fields in the neighborhood of the rupture area. The risk of future large earthquakes and tsunamis along the southern part of the Japan Trench seems exceptionally high, considering the stress change caused by Tohoku-oki earthquake with 9.0 Mw in 2011. This study necessitates the need to investigate the spatiotemporal relationship of large earthquakes from the perspectives of geology, seismology, and history.

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“…Tsunami deposits are useful for identifying tsunami events with more extended time scales, i.e., more than hundreds of years. Therefore, they are effective for detecting huge tsunami events with prolonged recurrence intervals (Goto et al 2021;Sawai 2012Sawai , 2020Sugawara et al 2012). Due to the Tohoku-oki earthquake and tsunami in 2011, considerable effort by scientific communities has been dedicated to elucidating paleo-tsunami events using tsunami deposits.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, the findings from the analyses of the deposits have been critical for the long-term risk assessment of huge tsunami events. Since the occurrence of Tohoku-oki event in 2011, many studies have been conducted along the coasts facing the central to northern parts of the Japan Trench to reevaluate paleo-tsunami histories (e.g., Goto et al 2015Goto et al , 2019Inoue et al 2017;Ishimura and Miyauchi 2015;Ishizawa et al 2018Ishizawa et al , 2019Kusumoto et al 2018;Minoura et al 2013;Sawai et al 2012Sawai et al , 2015Takada et al 2016;Takeda et al 2018;Tanigawa et al 2014aTanigawa et al , 2014bWatanabe et al 2014; see also Sawai 2017Sawai , 2020. For instance, Tanigawa et al (2014b) reported two event layers of the past 6000 years in a meadow of Misawa City, Shimokita Peninsula, Aomori Prefecture (Fig.…”

Section: Introductionmentioning

confidence: 99%

Three thousand year paleo-tsunami history of the southern part of the Japan Trench

Higaki

Goto

Yanagisawa

et al. 2021

Prog Earth Planet Sci

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This study conducted a field survey and multiproxy analyses on sediment cores retrieved from the Kobatake-ike pond in Choshi City, Chiba Prefecture, Japan. Kobatake-ike pond is located at a high elevation (i.e., 11 m above present-day sea level) and faces the southern part of the Japan Trench. Three event sand layers were detected within the continuous mud and peat sequences of 3000 years. Based on the multi-proxy analyses, including mineralogical composition, diatom assemblages, and geochemical markers, these sedimentological events were associated with past tsunamis. The most recent event was a sandy layer and is attributed to the AD 1677 Enpo tsunami, which was reported by an earlier study conducted in the pond. Our results demonstrated that two older sand layers are associated with large tsunamis that struck the Choshi area in AD 896–1445 and in BC 488–AD 215. In addition, the age ranges of these events seem to overlap that of large earthquakes and tsunamis known from the central part of the Japan Trench. This implies a possible spatiotemporal relation of earthquake generations between the central and southern parts of the Japan Trench. However, since the error ranges of the ages of tsunami deposits at the southern and central parts of the Japan Trench are still large, further investigation is required to clarify the relations of large earthquakes in both areas.

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Subduction zone paleoseismology along the Pacific coast of northeast Japan — progress and remaining problems

Cited by 35 publications

References 115 publications

Sensitivity Analysis for Seafloor Geodetic Constraints on Coseismic Slip and Interseismic Slip-Deficit Distributions

Sensitivity Analysis for Seafloor Geodetic Constraints on Coseismic Slip and Interseismic Slip-Deficit Distributions

Three thousand year paleo-tsunami history of the southern part of the Japan Trench

Three thousand year paleo-tsunami history of the southern part of the Japan Trench

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