Timing of Late Holocene Tsunamis Originated around the Southern Ryukyu Islands, Japan, Deduced from Coralline Tsunami Deposits

Kawana, Toshio; Nakata, Takashi

doi:10.5026/jgeography.103.4_352

Cited by 53 publications

(43 citation statements)

References 2 publications

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“…This result reinforces our interpretation that the group 2 boulders were deposited by repeated tsunamis. Kawana and Nakata (1994) (and see Goto et al, 2010b) also reported that the coralline boulders at the Sakishima Islands are useful to ascertain the occurrence of large tsunamis to 5000 yr B.P., the age of which is consistent with the time when the fringing reefs at the Sakishima Islands became stable. Therefore, we infer that large tsunamis, which could have moved >1-m-long boulders at least over the 1.5-km-wide reef, have struck the Sakishima Islands repeatedly during the past 5000 yr.…”

Section: Local Occurrence Of Large Tsunamis Along the Ryukyu Trenchmentioning

confidence: 85%

“…Numerous coastal boulders are deposited on the fringing reefs at each island (Kawana and Nakata, 1994;Goto et al, 2009Goto et al, , 2010aGoto et al, , 2010bGoto et al, , 2011. Differentiation of boulders according to whether they were deposited by tsunami or storm waves is controversial because many enigmatic boulders are present along rocky coasts or reefs throughout the world (e.g., Switzer and Burston, 2010;Buckley et al, 2012;Cox et al, 2012;Weiss, 2012).…”

Section: Introductionmentioning

confidence: 99%

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

Goto

Miyagi

Imamura

2013

Geology

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The occurrence of large earthquakes and tsunamis along the Ryukyu Trench is a subject of continuing interest, the key to which is the long-term geological record. Here we describe the clast size and spatial distributions of ~2900 boulders on the reefs of the Ryukyu Islands, Japan, as markers of paleotsunamis and causative tsunamigenic earthquakes. Boulders of tsunami origin were observed only at a specifi c island group at the southern end, suggesting the local occurrence of tsunamigenic earthquakes there. In contrast, in the central to northern Ryukyu Islands, no evidence exists of tsunamis larger than those at the southern end of the Ryukyu Islands during the past 2000-3000 yr. These islands have numerous boulders deposited by storm waves during the past 2300 yr or earlier. Their spatial distribution has not been disturbed by large tsunamis. This suggests that large tsunamis did not strike this area during that period; nevertheless, these regions are seismically active. Our study shows that coastal boulder deposits present great potential to not only ascertain the histories and effects of paleotsunamis but also to constrain fault models of the causative earthquakes.

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Section: Local Occurrence Of Large Tsunamis Along the Ryukyu Trenchmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

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

Goto

Miyagi

Imamura

2013

Geology

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“…A large number of massive boulders, locally called tsunami-ishi, are widely scattered along shorelines and on reefs in the southern Ryukyu region (e.g., Kawana and Nakata, 1994;Suzuki et al, 2008;Araoka et al, 2010;Goto et al, 2010a). These boulders, each consisting of a coral head, were likely transported from the back-reef moat onto the shore or reef by tsunamis (Goto et al, 2010a).…”

Section: Introductionmentioning

confidence: 99%

“…These boulders, each consisting of a coral head, were likely transported from the back-reef moat onto the shore or reef by tsunamis (Goto et al, 2010a). Several studies conducted in various regions of the world have proposed that it might be possible to date large prehistoric tsunami or storm events by determining the depositional ages of such boulders (e.g., Nott, 1997;Scheffers, 2004;Yu et al, 2004;Scicchitano et al, 2007), and Kawana and Nakata (1994) proposed on the basis of dated boulders that a large tsunami, which they called the "Sakishima tsunami," occurred ca. 2000 yr B.P.…”

Section: Introductionmentioning

confidence: 99%

Tsunami recurrence revealed by Porites coral boulders in the southern Ryukyu Islands, Japan

Araoka

Yokoyama

Suzuki

et al. 2013

Geology

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Information about past tsunami hazards, such as their recurrence interval and magnitude, is needed for future disaster prediction and mitigation. We examined radiocarbon ages of the surfaces of massive coral boulders cast ashore by past tsunamis in the southern Ryukyu Islands, Japan, where few historical and geological records of past tsunamis are available. We selected only non-eroded Porites coral boulders along the shoreline, because their characteristics make it possible to determine the probable timing of their deposition by tsunamis, and we applied a dating method that uses the cumulative probability distributions of large numbers of radiocarbon measurements of those boulders to determine the timing of past tsunamis. The results demonstrate that the southern Ryukyu Islands have repeatedly experienced tsunami events since at least 2400 yr ago, with a recurrence interval of ~150-400 yr. The largest Porites tsunami boulder that we studied (long axis, 9 m), which is probably the largest single-colony tsunami boulder in the world, was displaced by the A.D. 1771 Meiwa tsunami. Although the 1771 Meiwa tsunami was likely the largest event in at least the past 700 yr, calculations of current velocity show that all identifi ed tsunamis occurring before 1771 were probably large enough to cause considerable damage to human-built structures and loss of life. This study demonstrates that by reliably dating large numbers of selected coastal boulders it is possible to ascertain the timing, recurrence interval, and magnitude of past tsunamis in a location where few adequate survey sites of sandy tsunami deposits exist.

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“…Kawana (1996) suggested that several Holocene limestone boulders at the northern coast of Kikai-jima (Terrace IV) have been transported by tsunami. Such tsunami boulders are reported by Kawana and Nakata (1994) from the southern Ryukyu Islands. Based on 14 C dating of coral in these boulders they suggested that huge tsunami occurred periodically several times during the last 3000 years.…”

Section: Pedestalsmentioning

confidence: 73%

Surface lowering rates of uplifted limestone terraces estimated from the height of pedestals on a subtropical island of Japan

Matsukura

Maekado

Aoki

et al. 2007

Earth Surf Processes Landf

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In Kikai-jima, south-western Japan, many pedestal rocks have developed on the surface of Holocene raised coral-reef terraces with known dates of emergence. Pedestals are formed just under boulders, which are considered to have been transported by tsunami and settled on a reef flat before emergence. On the assumption that boulders protect the underlying limestone terrace from rainfall solution, the rate of surface lowering of these limestone terraces was evaluated from the height of pedestals and the period of their formation. The result showed that the mean lowering rate over 6000 years is 205 mm/ky. Figure 3. (a) History of altitude of each terrace. Since a few boulders on Terrace IV have no pedestals, it is considered that formation of pedestals starts when the height of terraces becomes higher than ca. 2 m above MSL. The amount of lowering of terrace surface due to solution after the uplift is ignored in this diagram. (b) Relation between the height of pedestals and the formative period, i.e., the surface lowering as a function of time. Surface lowering rates of uplifted limestone terraces estimated from the height of pedestals 1115

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Timing of Late Holocene Tsunamis Originated around the Southern Ryukyu Islands, Japan, Deduced from Coralline Tsunami Deposits

Cited by 53 publications

References 2 publications

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

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

Tsunami recurrence revealed by Porites coral boulders in the southern Ryukyu Islands, Japan

Surface lowering rates of uplifted limestone terraces estimated from the height of pedestals on a subtropical island of Japan

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