Localized tsunamigenic earthquakes inferred from preferential distribution of coastal boulders on the Ryukyu Islands, Japan

Goto, Kazuhisa; Miyagi, Kunimasa; Imamura, Fumihiko

doi:10.1130/g34823.1

Cited by 40 publications

(44 citation statements)

References 21 publications

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“…The 1771 tsunami was an extremely large event, but historical documents show that it damaged only a restricted area, the Sakishima Islands, including Ishigaki Island (Goto et al 2010). Based on the clast sizes and spatial distributions of boulders on the reefs of the Ryukyu Islands, Goto et al (2013) suggested that large tsunamis have struck locally but repeatedly around the Sakishima Islands, but not around the Amami and Okinawa Islands, at least during the past 2300 years.…”

Section: Study Areamentioning

confidence: 99%

Using molluscan assemblages from paleotsunami deposits to evaluate the influence of topography on the magnitude of late Holocene mega-tsunamis on Ishigaki Island, Japan

Kitamura

Ito

Ikuta

et al. 2018

Prog Earth Planet Sci

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Four ancient tsunami deposits were identified in a trench excavated on Ishigaki Island, Okinawa, Japan. Three of the tsunami deposits (T-I, T-II, and T-IV) consist of calcareous sand beds, whereas the other (T-III, located stratigraphically between T-II and T-IV) consists of boulders. Deposit T-I was caused by a tsunami in 1771.14 C dating, together with the elevations of the landward margins of these sandy tsunami deposits, suggests that tsunamis II and IV were similar in size to the 1771 tsunami, although the influence of local topographic features on the magnitudes of tsunamis has not yet been examined. This study reconstructs the local topographic features by comparing the molluscan assemblages incorporated within the tsunami deposits with those in recent beach deposits. The presence of species that inhabit the intertidal zone in lagoonal settings in all the assemblages indicates that the present-day shallow lagoon has been present off the study area since the occurrence of tsunami T-IV, which supports the previous hypothesis that the magnitudes of the 1771 tsunami and tsunamis II and IV were similar. These molluscan assemblages also suggest that a high relative abundance of large, heavy mollusc shells is a feature of the paleotsunami deposits in the coastal lowlands found along the shallow coral lagoons.

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Section: Study Areamentioning

confidence: 99%

Using molluscan assemblages from paleotsunami deposits to evaluate the influence of topography on the magnitude of late Holocene mega-tsunamis on Ishigaki Island, Japan

Kitamura

Ito

Ikuta

et al. 2018

Prog Earth Planet Sci

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“…Dawson and Shi 2000). Offshore, the tsunami-derived material is distributed more evenly and occupies broader areas than the sediments deposited by tropical storms (Paris et al 2009;Goto et al 2013). A comparable thickness of the stromatoporoid beds between the sections and a lack of lateral size segregation of the stromatoporoids resemble the above-described modern boulder distribution, governed mainly by sea bottom topography.…”

Section: Stromatoporoid Beds -Distributionmentioning

confidence: 94%

“…Goto et al 2013), which are frequently exposed to both tsunami waves and tropical storms. Boulders of tsunami origin were transported there over a distance of more than 1 km landward from the reef crest, whereas the occurrence of those deposited by hurricanes is limited to a narrow strip (~ 200m) on the leeward side of the reef (Goto et al 2010a).…”

Section: Stromatoporoid Beds -Distributionmentioning

confidence: 99%

Stromatoporoid Beds and Flat-Pebble Conglomerates Interpreted as Tsunami Deposits in the Upper Silurian of Podolia, Ukraine

Łuczyński¹,

Skompski²,

Kozłowski³

2014

Acta Geologica Polonica

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ABSTRACT:Łuczyński, P., Skompski, S. and Kozłowski, W. 2014. Stromatoporoid beds and flat-pebble conglomerates interpreted as tsunami deposits in the Upper Silurian of Podolia, Ukraine. Acta Geologica Polonica, 64 (3), 261-280. Warszawa.Tsunami deposits are currently a subject of intensive studies. Tsunamis must have occurred in the geological past in the same frequency as nowadays, yet their identified depositional record is surprisingly scarce. Here we describe a hitherto unrecognized example of probable palaeotsunamites.The Upper Silurian (Pridoli) carbonate succession of Podolia (southwestern Ukraine) contains variously developed event beds forming intercalations within peritidal deposits (shallow water limestones, nodular marls and dolomites). The event beds are represented by stromatoporoid and fine-grained bioclastic limestones, in some places accompanied by flat-pebble conglomerates. The interval with event beds can be traced along the Zbruch River in separate outcrops over a distance of more than 20 km along a transect oblique to the palaeoshoreline. The stromatoporoid beds have erosional bottom surfaces and are composed of overturned and often fragmented massive skeletons. The material has been transported landward from their offshore habitats and deposited in lagoonal settings. The flat-pebble conglomerates are composed of sub-angular micritic clasts that are lithologically identical to the sediments forming the underlying beds.Large-scale landward transport of the biogenic material has to be attributed to phenomena with very high energy levels, such as tropical hurricanes or tsunamis. This paper presents a tsunamigenic interpretation. Morphometric features of redeposited stromatoporoids point to a calm original growth environment at depths well below storm wave base. Tsunami waves are the most probable factor that could cause their redeposition from such a setting. The vastness of the area covered by parabiostromal stromatoporoid beds resembles the distribution of modern tsunami deposits in offshore settings. The stromatoporoid beds with unsorted stromatoporoids of various dimensions evenly distributed throughout the thickness of the beds and with clast-supported textures most probably represent deposition by traction. In some sections, the stromatoporoids are restricted to the lowermost parts of the beds, which pass upwards into bioclastic limestones. In this case, the finer material was deposited from suspension. The coexistence of stromatoporoid beds and flat-pebble conglomerates also allows presenting a tsunami interpretation of the latter. The propagating tsunami waves, led to erosion of partly lithified thin-layered mudstones, their fragmentation into flat clasts and redeposition as flat-pebble conglomerates.

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“…The vastness of the area covered by the parabiostromal beds and the lack of stromatoporoid lateral size segregation resembles the distribution of modern tsunami-derived material and differs from storm derived deposits (comp. Paris et al 2009;Goto et al 2007Goto et al , 2013. The material was transported both by traction by the oncoming tsunami waves (clast supported varieties), and from suspension, probably during backwash flows (bioclastic limestones with the material derived from shallow-water areas) (comp.…”

Section: Tsunami Interpretation Of Stromato-poroid Beds and Flat-pebbmentioning

confidence: 99%

Recent studies on the Silurian of the western part of Ukraine

Łuczyński

Skompski²,

Kozłowski³

2016

Acta Geologica Polonica

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ABSTRACT:Łuczyński, P., Skompski, S. and Kozłowski, W. 2016. Recent studies on the Silurian of the western part of Ukraine. Acta Geologica Polonica, 66 (3), 281-297. Warszawa.The paper summarises the effects of recent studies carried out by a team from the Department of Historical and Regional Geology of the Faculty of Geology, University of Warsaw on the upper Silurian of Podolia (western part of Ukraine).The sedimentary history of the Silurian succession of Podolia is characterised by its cyclic pattern, with shallowing-upward cyclothems. In the traditional interpretation, the occurrence of stromatoporoid beds within each cyclothem marks the deepest (or most open-marine) sedimentary environment within the cycle. According to the results of recent studies, their occurrence is connected rather with a relatively shallow-water environment and with high energy phenomena. A substantial reinterpretation of the main sedimentary processes governing the deposition and facies distribution on the shelf is presented. Particularly, there are recognised and described high-energy sedimentary events repeatedly punctuating the generally calm sedimentation that prevailed in the lagoonal settings, some of which are interpreted as tsunami induced.Further perspectives for studies on the Silurian successions of Podolia are also discussed. The main problem is the precise correlation of particular sections that are scattered over vast distances and developed in similar facies associations.

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Localized tsunamigenic earthquakes inferred from preferential distribution of coastal boulders on the Ryukyu Islands, Japan

Cited by 40 publications

References 21 publications

Using molluscan assemblages from paleotsunami deposits to evaluate the influence of topography on the magnitude of late Holocene mega-tsunamis on Ishigaki Island, Japan

Using molluscan assemblages from paleotsunami deposits to evaluate the influence of topography on the magnitude of late Holocene mega-tsunamis on Ishigaki Island, Japan

Stromatoporoid Beds and Flat-Pebble Conglomerates Interpreted as Tsunami Deposits in the Upper Silurian of Podolia, Ukraine

Recent studies on the Silurian of the western part of Ukraine

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