南西北海道，石狩低地帯におけるテフラ層序学：

Nakagawa, Mitsuhiro; Amma-Miyasaka, Mizuho; Miura, Daisuke; Uesawa, Shimpei

doi:10.5575/geosoc.2018.0038

Cited by 17 publications

(15 citation statements)

References 15 publications

(1 reference statement)

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“…The left-hand side of the scarp, which is located near the ridge of the hill slope and did not collapse due to its shallower dip angle, exhibits a stratigraphic sequence of pyroclastic deposits originating from the Tarumai Volcano. We identified deposits Ta-b (AD 1667) 3,4 , Ta-c (ca. 2.5 ka), and Ta-d (ca.…”

Section: Field Investigation Of Landslidesmentioning

confidence: 97%

“…A total of 41 people were killed during the earthquake, with most of these (36 people) perishing in landslides near the epicenter. The hills in southwestern Hokkaido are widely covered by volcanic deposits, derived from the repeated eruptions of nearby volcanoes such as Tarumai, Eniwa, and Shikotsu 1–4 . In addition to intermittent rainfall over a period of several weeks before the earthquake, Typhoon Jebi caused heavy rainfall on 4 September in this area (Fig.…”

Section: Introductionmentioning

confidence: 99%

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Fluidized landslides triggered by the liquefaction of subsurface volcanic deposits during the 2018 Iburi–Tobu earthquake, Hokkaido

Kameda

Kamiya

Masumoto

et al. 2019

Sci Rep

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The 6.6 Mw Iburi–Tobu earthquake struck southern Hokkaido, Japan on 6 September 2018. The earthquake triggered widespread slope collapses in the hills near the epicenter, resulting in destructive landslides that killed 36 people. Volcanic deposits covering the region slid downhill in a flow-like manner suggestive of fluidized landslides. Here, we report a distinctive example of liquefaction in the field, which could be a prerequisite for the generation of fluidized landslides triggered by large earthquakes. In the scarp of a typical landslide, an altered halloysite-bearing volcanic layer is observed at a level almost coincident with the sliding surface. The layer is intensely undulating and can be divided into an upper clay-rich layer and a lower pumice-rich layer, suggesting that the altered layer had liquefied as a result of the strong coseismic ground motion. The layer had been soaked by heavy rainfall just one day before the earthquake and could have liquefied, producing a weak and slippery plane, resulting in the catastrophic landslides in this area.

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Section: Field Investigation Of Landslidesmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Fluidized landslides triggered by the liquefaction of subsurface volcanic deposits during the 2018 Iburi–Tobu earthquake, Hokkaido

Kameda

Kamiya

Masumoto

et al. 2019

Sci Rep

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“…2). The ground is mostly covered by several layers of volcanic ash, pumice, and scoria, with alternations of andosols, underlain by Miocene to Pleistocene sedimentary rocks (Yanai 1989;Ozaki et al 2014;Nakagawa et al 2018). These volcanic products originated from the Kuttara, Shikotsu, Eniwa, and Tarumae volcanoes located 50 to 70 km southwest of the area.…”

Section: Study Areamentioning

confidence: 99%

“…Most of the landslides observed in the area after the earthquake were shallow landslides, occurring on both concave and convex slopes. Low ridges separating small catchments allowed individual landslides to coalesce at many locations (e.g., 9,000 ybp (Yanai 1989;Nakagawa et al 2018). Figure 6 is a photograph of a landmass that slipped over the base of Ta-d layer (orange-brown) on the slope.…”

Section: Study Areamentioning

confidence: 99%

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Topographic effects on frequency-size distribution of landslides triggered by the Hokkaido Eastern Iburi Earthquake in 2018

Kasai

Yamada

2019

Earth Planets Space

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This study examined the frequency-size distribution of 6117 landslides spread over 440 km 2 in Iburi Subprefecture, Hokkaido, Japan, induced by the Hokkaido Eastern Iburi Earthquake (M w 6.6) on September 6, 2018. The study area is characterized by gently undulating terrain that is finely dissected by shallow streams and covered predominantly by layers of volcanic products with high water content. Most of the landslides were shallow landslides, and their slip surfaces often formed in a layer of volcanic soil called the "Ta-d, " deposited at 9000 ybp. Low ridges separating small catchments allowed individual landslides to coalesce in many locations. The average size of landslides was 7160 m 2. Landslide size tended to increase with slope angle up to 20° to 25° and then decrease with further increase of slope angle. About half of the landslides occurred in a feature with both concave planform and profile curvature, and their average size was 8720 m 2. In contrast, 17% of the total landslides occurred in the case of both curvatures being convex, and their average size was 5190 m 2. The results indicated that the accumulation of saturated soil in concave features provided more opportunities for landslides of large sizes. The frequency-size distribution of the landslides presented high rollover, 5.0 × 10 −3 km 2 , but the exponent of power law decay for medium to large landslides, − 2.46, was not largely different from those of studies in other locations. Compared with other seismically caused examples, the landslides triggered by the Hokkaido Eastern Iburi Earthquake can be characterized as more clustered, more numerous, and larger in size for the moment magnitude of the earthquake. Conversely, the magnitude scale for the landslide event estimated from the total landslide area was equivalent to that of a region struck by an earthquake of M w = 7.0 to 7.4. This study demonstrated that gently undulating regions can produce unexpectedly large and frequent landslides when struck by an intense earthquake, and when soil layers vulnerable to ground shaking cover the ground.

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Pressure Head Dynamics on a Natural Slope in Eastern Iburi Struck by the 2018 Hokkaido Earthquake

Aoki

Katsura

Yoshino

et al. 2020

Understanding and Reducing Landslide Disaster Risk

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南西北海道，石狩低地帯におけるテフラ層序学：

Cited by 17 publications

References 15 publications

Fluidized landslides triggered by the liquefaction of subsurface volcanic deposits during the 2018 Iburi–Tobu earthquake, Hokkaido

Fluidized landslides triggered by the liquefaction of subsurface volcanic deposits during the 2018 Iburi–Tobu earthquake, Hokkaido

Topographic effects on frequency-size distribution of landslides triggered by the Hokkaido Eastern Iburi Earthquake in 2018

Pressure Head Dynamics on a Natural Slope in Eastern Iburi Struck by the 2018 Hokkaido Earthquake

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