Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Hironobu Kan Last modified date:2023.11.22

Professor / Basic Structure of Human Societies / Department of Environmental Changes / Faculty of Social and Cultural Studies

1. Katagiri, C., Nakanishi, Y., Yoshizaki, S., Kimura, H., Kan, H., Reconstructing a WWII underwater wreck site: the battle of the destroyer USS Emmons and Japanese Special Attack Airplanes, International Journal of Nautical Archaeology,, 1-21, 2022.06.
2. Minamidate, K., Goto, K., Kan, H., Numerical estimation of maximum possible sizes of paleo-earthquakes and tsunamis from storm-derived boulders, Earth and Planetary Science Letters,, Volume 579, Article 117354, 2022.02.
3. Minamidate, K., Goto, K., Watanabe, M., Roeher, V., Toguchi, K., Sannoh, M., Nakashima, Y., Kan, H., Millennial scale maximum intensities of typhoon and storm wave in the northwestern Pacific Ocean inferred from storm deposited reef boulders, Scientific Reports,, 2020.04.
4. Fujita, K., Yagioka, N., Nakada, C., Kan, H., Miyairi, Y., Yokoyama, Y., Webster, J.M., Reef-flat and back-reef development in the Great Barrier Reef caused by rapid sea-level fall during the Last Glacial Maximum (30–17 ka), Geology,, 48, 1, 39-43, 2020.01.
5. Kimura, H., Yokota, K., Aizawa, J., Kan, H., Yoshimura, K., Depositional Environments of Aragonite Speleothem in Maboroshi-no-Shonyudo, Taishaku, Hiroshima Prefecture, Japan. Journal of the Speleological Society of Japan, Journal of the Speleological Society of Japan, 44, 21-36, 2019.12.
6. Minamidate, K., Goto, K., Watanabe, M., Roeber, V.,Toguhi, K., Sannoh, M., Nakashima, Y., Kan, H., Importance of high-resolution 3D topography for wave simulation, Proceedings of the 2019 CWMD Conference, 214-220, 2019.09.
7. Vila-Concejo, A., Scambary, L., Johansson, L., Duce, S.J., Hamylton, S. Webster, J., Salles, T., Fujita, K., Kan, H., Wave dissipation and lagoon infilling in the southern Great Barrier Reef, International Conference on Coastal Sediments 2019, 10.1142/9789811204487_0089, 1020-1028, 2019.05.
8. Humblet, M., Potts, D.C., Webster, J.M., Braga, J.C., Iryu, Y., Yokoyama, Y., Bourillot, R.7, Séard, C, Droxler, A., Fujita, K., Gischler, E., and Kan, H., Late glacial to deglacial variation of coralgal assemblages in the Great Barrier Reef, Australia, Global and Planetary Change,, 174, 70-91, 2019.03.
9. Yagioka, N., Nakada, C., Fujita, K., Kan, H., Yokoyama, Y., Webster, J. M., Depositional environments beneath the shelf-edge slopes of the Great Barrier Reef, inferred from foraminiferal assemblages: IODP Expedition 325, Palaeogeography, Palaeoclimatology, Palaeoecology,, 514, 386-397, 2019.01.
10. Yokoyama, Y., Esat, T.M., Thompson, W.G., Thomas, A.L., Webster, J.M., Miyairi, Y., Sawada, S., Aze, T., Matsuzaki, H., Okuno, J., Fallon, S., Braga, J-C., Humblet, M., Iryu, Y., Potts, D.C., Fujita, K., Suzuki, A., Kan, H., Rapid glaciation and a two-step sea-level plunge into The Last Glacial Maximum, Nature,, 559, 603-607, 2018.07, The approximately 10,000-year-long Last Glacial Maximum, before the termination of the last ice age, was the coldest period in Earth’s recent climate history1. Relative to the Holocene epoch, atmospheric carbon dioxide was about 100 parts per million lower and tropical sea surface temperatures were about 3 to 5 degrees Celsius lower2,3. The Last Glacial Maximum began when global mean sea level (GMSL) abruptly dropped by about 40 metres around 31,000 years ago4 and was followed by about 10,000 years of rapid deglaciation into the Holocene1. The masses of the melting polar ice sheets and the change in ocean volume, and hence in GMSL, are primary constraints for climate models constructed to describe the transition between the Last Glacial Maximum and the Holocene, and future changes; but the rate, timing and magnitude of this transition remain uncertain. Here we show that sea level at the shelf edge of the Great Barrier Reef dropped by around 20 metres between 21,900 and 20,500 years ago, to −118 metres relative to the modern level. Our findings are based on recovered and radiometrically dated fossil corals and coralline algae assemblages, and represent relative sea level at the Great Barrier Reef, rather than GMSL. Subsequently, relative sea level rose at a rate of about 3.5 millimetres per year for around 4,000 years. The rise is consistent with the warming previously observed at 19,000 years ago1,5, but we now show that it occurred just after the 20-metre drop in relative sea level and the related increase in global ice volumes. The detailed structure of our record is robust because the Great Barrier Reef is remote from former ice sheets and tectonic activity. Relative sea level can be influenced by Earth’s response to regional changes in ice and water loadings and may differ greatly from GMSL. Consequently, we used glacio-isostatic models to derive GMSL, and find that the Last Glacial Maximum culminated 20,500 years ago in a GMSL low of about −125 to −130 metres..
11. Kan, H., Katagiri, C., Nakanishi, Y., Yoshizaki, S., Nagao, M., Ono, R., Assessment and significance of a World War II battle site: recording the USS Emmons using a high-resolution DEM combining multibeam bathymetry and SfM photogrammetry, The International Journal of Nautical Archaeology, 10.1111/1095-9270.12301, 47, 2, 267-280, 2018.06, The USS Emmons, a 106m US Navy Gleaves‐class destroyer minesweeper that sank in 40m of water off Okinawa Island, Japan after kamikaze attack in 1945, is used as a case study for examining the history, multivocal significance, and heritage management of a World War II naval battle site. A baseline record of the site was made using an innovative method incorporating precise control points obtained from high‐resolution multibeam echosounding bathymetry to generate 3D models using structure‐from‐motion photogrammetry. The 3D models produced can be used for sharing information about this underwater cultural heritage and for future in situ monitoring of the archaeological remains..
12. Webster,J.M., Braga, J.C., Humblet, M., Potts, D.C., Iryu, Y., Yokoyama, Y., Fujita, K., Bourillot, R., Esat, T.M., Fallon, S., Thompson, W.G., Thomas, A.L., Kan, H., McGregor, H.V., Hinestrosa, G., Obrochta, S.P., Lougheed, B.C., Response of the Great Barrier Reef to sea-level and environmental changes over the past 30,000 years., Nature Geoscience,, 2018.05, [URL], Previous drilling through submerged fossil coral reefs has greatly improved our understanding of the general pattern of sea-level change since the Last Glacial Maximum, however, how reefs responded to these changes remains uncertain. Here we document the evolution of the Great Barrier Reef (GBR), the world’s largest reef system, to major, abrupt environmental changes over the past 30 thousand years based on comprehensive sedimentological, biological and geochronological records from fossil reef cores. We show that reefs migrated seaward as sea level fell to its lowest level during the most recent glaciation (~20.5–20.7 thousand years ago (ka)), then landward as the shelf flooded and ocean temperatures increased during the subsequent deglacial period (~20–10 ka). Growth was interrupted by five reef-death events caused by subaerial exposure or sea-level rise outpacing reef growth. Around 10 ka, the reef drowned as the sea level continued to rise, flooding more of the shelf and causing a higher sediment flux. The GBR’s capacity for rapid lateral migration at rates of 0.2–1.5 m yr−1 (and the ability to recruit locally) suggest that, as an ecosystem, the GBR has been more resilient to past sea-level and temperature fluctuations than previously thought, but it has been highly sensitive to increased sediment input over centennial–millennial timescales..
13. Miklavič, B., Yokoyama, Y., Urata, K., Miyairi, Y., Kan, H., Holocene relative sea level history from phreatic overgrowths on speleothems (POS) on Minami Daito Island, Northern Philippine Sea., Quaternary International,, 471, 359-368, 2018.04.
14. Ono, R., Katagiri, C., Kan, H., Nagao, M., Nakanishi, Y., Yomamoto, Y., Takemura, F., Sakagami, N., Discovery of Iron Grapnel Anchors in Early Modern Ryukyu and Management of Underwater Cultural Heritages in Okinawa, Japan, International Journal of Nautical Archaeology, 10.1111/1095-9270.12145, 45, 75-91, 2016.01, The Yarabuoki underwater site contains seven iron grapnel anchors and Early Modern Okinawan ceramic jars and is dated to the 16th–19th centuries. The site lies at a depth of 12–32 m off the western coast of Ishigaki Island in Okinawa, Japan. Based on underwater archaeological and broadband multibeam surveys, as well as historical research of the artefacts and Early Modern Ryukyuan shipping, we discuss the possible anchor and vessel types in Ryukyu and Eastern Asia in EarlyModern times.We also discuss the efficacy of low-costROV for assisting surveys in shallow-water environments and the value of educational programmes for promoting the management and conservation of underwater cultural heritage..
15. Hamanaka, N., Kan, H., Nakashima, Y., Yokoyama, Y., Okamoto, T., Ohashi, T., Adachi, H., Matsuzaki, H., Hori, N., Holocene reef-growth dynamics on Kodakara Island (29 degrees N, 129 degrees E) in the Northwest Pacific, Geomorphology, 10.1016/j.geomorph.2015.04.011, 243, 27-39, 2015.08, The spatial distribution of modern coral reefs in the Northwest Pacific (NWP) is restricted to approximately 30°N. Understanding the high-latitude reef-growth process and its correlation to climate change may provide important insights into future reef growth at even higher latitudes in response to globalwarming.We conducted field surveys and obtained seven cores from the raised reefs of Kodakara Island (29°N, 129°E) in the NWP to determine the changes in and response of reef growth dynamics to millennial-scale climate change through the Holocene. To reconstruct the timing of the reef growth, 37 coral ageswere determined using acceleratormass spectrometry (AMS) radiocarbon dating.
The island is characterized by three Holocene reef terraces (Terraces I to III), which were uplifted ca. 2.4 ka, 1.0–0.4 ka, and in the modern era. Three growth hiatuses occurred circa 5.9–5.8 ka, 4.4–4.0 ka, and 3.3–3.2 ka, which correlate with millennial-scale climate changes (Hamanaka et al., 2012). The reef growth began at least 8 ka. Relatively rapid vertical growth of 3.6–3.3 m kyr−1 occurred between 8 and 6 ka. The reef started growing near land and then gradually extended seaward. The reef growth around the reef slope decelerated after 6 ka
and most likely coincided with the first and second hiatuses detected landward. In contrast with the reef flat, which resumed its growth after the third hiatus event, the reef mound accretion on the slope ceased definitively. Terrace I was uplifted ca. 2.4 ka. The reef growth reactivated ca. 1.3 ka, and the reef grewat a rate of 9.1m kyr−1 between 1.3 and 1.0 ka; this rate is the fastest growth recorded in this study. This time interval corresponds to the Medieval Climatic Anomaly (MCA). The cause of the delayed reef growth between 2.4 and 1.4 ka remains unclear, but itmay imply the existence of a late Holocene hiatus due to a weaker Kuroshio Current (KC) ca. 1.7 ka and to strong El Niño-Southern Oscillation (ENSO) activity between 2 and 1.5 ka in the East Pacific. The timing of the hiatuses agrees with theweakening of the KC and themore frequent El Niño events during the positive phase of the Pacific Decadal Oscillation (PDO), whereas the rapid growth coincides with La Niña conditions, such as the MCA, during the negative phase of the PDO. Our results indicate that the climate event at approximately 4 ka caused the largest change in the reef growth, and it may have affected reefs throughout the Pacific region. Specifically, the ENSO and PDO phases may have impacted the reef growth and KC behavior..
16. Kan, H., Urata, K., Nagao, M., Hori, N., Fujita, K., Yokoyama, Y., Nakashima, Y., Ohashi, T., Goto, K., Suzuki, A., Submerged karst landforms observed by multibeam bathymetric survey in Nagura Bay, Ishigaki Island, southwestern Japan., Geomorphology, DOI: 10.1016/j.geomorph.2014.07.032, 229, 112-124, 2015.01, Submerged tropical karst features were discovered in Nagura Bay on Ishigaki Island in the southern Ryukyu Islands, Japan. The coastal seafloor at depths shallower than ~130 m has been subjected to repeated and alternating subaerial erosion and sedimentation during periods of Quaternary sea-level lowstands. We conducted a broadband multibeam survey in the central area of Nagura Bay (1.85 × 2.7 km) and visualized the high-resolution bathymetric results over a depth range of 1.6–58.5 m. Various types of humid tropical karst landforms were found to coexist within the bay, including fluviokarst, doline karst, cockpit karst, polygonal karst, uvalas, and mega-dolines. Although these submerged karst landforms are covered by thick postglacial reef and reef sediments, their shapes and sizes are distinct from those associated with coral reef geomorphology. The submerged landscape of Nagura Bay likely formed during multiple glacial and interglacial periods. According to our bathymetric results and the aerial photographs of the coastal area, this submerged karst landscape appears to have developed throughout Nagura Bay (i.e., over an area of approximately 6 × 5 km) and represents the largest submerged karst in Japan..
17. Ono, R., Kan, H., Sakagami, N., Nagao, M., Katagiri, C., First Discovery and Mapping of Early Modern Grapnel Anchors in Ishigaki Island and Cultural Resource Management of Underwater Cultural Heritage in Okinawa., Proceedings of the 2nd Asia-Pacific Regional Conference on Underwater Cultural Heritage, 2, 683-696, 2014.05.
18. Sowa, K., Watanabe, T., Kan, H., Yamano, H., Influence of Land Development on Holocene Porites Coral Calcification at Nagura Bay, Ishigaki Island, Japan, PLOS ONE, 10.1371/journal.pone.0088790, 9, 2, 2014.02, To evaluate the relationships between coral calcification, thermal stress, and sedimentation and eutrophication linked to
human impact (hereafter referred to as ‘‘land development’’) by river discharge, we analyzed growth characteristics in the
context of a paleoenvironment that was reconstructed from geochemical signals in modern and fossil (1.2 cal kyr BP and
3.5 cal kyr BP, respectively) massive Porites corals from Nagura Bay (‘‘Nagura’’) and from modern Porites corals from the
estuary of the Todoroki River, Shiraho Reef (‘‘Todoroki’’). Both sites are on Ishigaki Island, Japan, and Nagura is located
approximately 12 km west of Todoroki. At Nagura, the individual corals provide time windows of 13 (modern), 10 (1.2 cal
kyr BP), and 38 yr in length (3.5 cal kyr BP). Here, we present the coral annual calcification for Nagura and Todoroki, and (bi)
monthly resolved records of Sr/Ca (a proxy of sea surface temperature (SST)) and Ba/Ca (a proxy of sedimentation and
nutrients related to land development) for Nagura. At Nagura, the winter SST was cooler by 2.8uC in the 1.2 cal kyr BP, and
the annual and winter SSTs in the 3.5 cal kyr BP were cooler by 2.6uC and 4.6uC, respectively. The annual periodicity of Ba/Ca
in modern coral is linked to river discharge and is associated with land development including sugar cane cultivation.
Modern coral calcification also has declined with SST warming and increasing Ba/Ca peaks in winter. However, calcification
of fossil corals does not appear to have been influenced by variations in Sr/Ca and Ba/Ca. Modern coral growth
characteristics at Nagura and Todoroki indicate that coral growth is both spatially and temporally influenced by river
discharge and land development. At Nagura, our findings suggest that land development induces negative thermal
sensitivity for calcification in winter due to sugar cane harvest, which is a specifically modern phenomenon..
19. Inoue, M, Shinmen, K., Kawahata, H., Nakamura, T., Tanaka, Y., Kato, A., Shinzato, C., Iguchi, A., Kan, H., Suzuki, A., Sakai, K., Estimate of calcification responses to thermal and freshening stresses based on culture experiments with symbiotic and aposymbiotic primary polyps of a coral, Acropora digitifera, GLOBAL AND PLANETARY CHANGE, 10.1016/j.gloplacha.2012.05.001, 92-93, 1-7, 2012.07, Although coral calcification is directly related to coral health, few studies have examined the responses of
coral calcification to environmental stresses, with the exception of ocean acidification. In this study, we experimentally
exposed aposymbiotic (lacking symbionts) and symbiotic primary polyps of the scleractinian
coral Acropora digitifera to several seawater temperatures (27, 29, 31, and 33 °C) and salinities (26, 28, 30,
32, and 34) to investigate the effects of thermal and freshening stresses on coral calcification from the standpoint
of coral-algal symbiosis. Calcification rates were higher for symbiotic versus aposymbiotic polyps in
both sets of experiments, except for those reared at 31 °C and 33 °C. Calcification responses of symbiotic
polyps were a non-linear function of temperature, and the threshold temperature affecting skeletal growth
and bleaching was between 29 °C and 31 °C. Calcification rates of aposymbiotic polyps were also a nonlinear
function of temperature, with a maximum polyp weight at 31 °C, suggesting that thermal stress also
did some damage to the coral host itself. In contrast, skeletal growth of both aposymbiotic and symbiotic
polyps decreased linearly with increased salinity. Observations of the microstructure of polyp samples
revealed a clearly cyclic feature of skeletal surfaces that was likely related to organo-mineral deposition of
calcium carbonate even under lowered-salinity conditions. However, neither type of polyp reared at 33 °C
evidenced this characteristic, suggesting that thermal stress had compromised the normal calcification process,
which involves secretion of an organic matrix by the coral host. Our results suggest that the effects of
future global warming will include a reduction in coral calcification itself and the collapse of coral-algal symbiosis,
at least at the primary polyp stage. The present experiments showed that thermal stress would affect
the host's physiological functionality, whereas freshening stress, which is simply the dilution of ambient
seawater, would affect the mineralization process associated with coral calcification..
20. Seki, A., Yokoyama, Y., Suzuki, A., Kawakubo, Y., Okai, T., Miyairi, Y., Matsuzaki, H., Namizaki, N., Kan, H., Mid-Holocene sea-surface temperature reconstruction using fossil corals from Kume Island, Ryukyu, Japan., Geochemical Journal, 46, e27-e32, 2012.05, The relative warmth and stability of the Holocene was punctuated by several brief cold events. Whereas these cold
events on a global scale are widely reported, the lack of records from regions such as the East China Sea (ECS) results in
an incomplete understanding of the underlying cooling mechanism.
Here, we present a coral-based paleo-SST (sea-surface temperature) reconstruction from the ECS to constrain Holocene
variability in the Kuroshio Western Boundary Current and the East Asian Monsoon (EAM). Our new data confirm that
cold conditions prevailed at 3.8 cal kyr BP, which is consistent with the previously-reported Pulleniatina Minimum Event
(PME). While this previous reconstruction could not reveal seasonal differences, our high-resolution data indicate a differing
seasonal SST response between summer and winter. This result provides an important insight into understanding
the mechanism of the millennium scale cold event in the ECS, the region affected by EAM..
21. Hamanaka, N., Kan, H., Yokoyama, Y., Okamoto, T., Nakashima, Y., Kawana, T., Disturbances with hiatuses in high-latitude coral reef growth during the Holocene: Correlation with millennial-scale global climate change, GLOBAL AND PLANETARY CHANGE, 10.1016/j.gloplacha.2011.10.004, 80-81, 21-35, 2012.01, Recent studies have reported Holocene millennial-scale climate instability at a global scale. However, the relationship
between this climate variability and coral reef growth is still unclear. Field observations and highprecision,
in situ coral radiocarbon dating of the excavated trench walls of an uplifted middle-to-late Holocene
coral reef on Kodakara Island, located in the pathway of the Kuroshio Current in the northwestern Pacific,
show evidence of the existence of disturbances with hiatuses in coral reef growth and coral composition differences
before and after the disturbances.We found three disconformities in the reef, and the dating results indicate
that disturbances with hiatuses in reef growth occurred at approximately 5.9 to 5.8, 4.4 to 4.0, and 3.3 to
3.2 cal yr B.P. The results also indicate that the second and third eventswere associatedwith sea-level oscillation.
The timing of the disturbances corresponds well with the periods when the Kuroshio Current was relatively
weak andwas associatedwith a relatively cold sea surface temperature,which may have enhanced the cold winter
Asian monsoons, and with Holocene North Atlantic ice-rafting cold events. The coral composition clearly
changed before and after the disturbances, with gradually reduced diversity resulting in a reef dominated by
acroporiid coral. These data led to the hypothesis that coral reef growth was interrupted by suborbital
millennial-scale global climate change induced by persistent solar activity during the Holocene in highlatitude
coral reefs, such as those in the Northwest Pacific, leading to low diversity in the reefs that experienced
each disturbance. Our results may provide new insights into theories of past and future coral reef formation
22. Riyaz, M., Park, K.-H., Ali, M., Kan, H., Influence of geological setting of islands and significance of reefs for tsunami wave impact on the Atoll Islands, Maldives, BULLETIN OF ENGINEERING GEOLOGY AND THE ENVIRONMENT, 10.1007/s10064-010-0278-y, 69, 3, 443-454, 2010.08, This paper discusses the influence of the geological
setting of islands and reefs in the Maldives on the
impact of the 26 December 2004 Indian Ocean Tsunami.
Geological and geomorphological data (including orientation,
location, size, ellipticity, reef-island distance, proportion
of reef area to island area) were collected for
completely flooded and\25% flooded islands. The results
show that although the different parameters may interact to
reduce or magnify the impact, the reef-island distance is
the most important factor. The critical minimum distance
between the reef and the island shoreline required for the
wave to set up is estimated as 89 m on the eastern and
140 m on the western sides of the island, respectively.
Circular islands with short reef-island distance and small
percent of reef area seem to be safer in the context of
tsunami. The result of this study can be applied to identify
islands that are naturally protected/resilient against natural
disasters such as tsunami and those where the hazard is
23. Araoka, D., Inoue, M., Suzuki, A., Yokoyama, Y., Edwards, R.L., Cheng, H., Matsuzaki, H., Kan, H., Shikazono, N., Kawahata, H., Historic 1771 Meiwa tsunami confirmed by high-resolution U/Th dating of massive Porites coral boulders at Ishigaki Island in the Ryukyus, Japan, GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 10.1029/2009GC002893, 11, 1-11, 2010.06, The chronicles of the Ryukyu Kingdom describe at least four coastal inundation events at Ishigaki
Island during the seventeenth through nineteenth centuries: the 1771 Meiwa earthquake tsunami, which
killed 12,000 people; another earthquake tsunami (1687); and two events with unrecorded causes (1625
and 1714). We used a high‐resolution U/Th method to date well‐preserved surface parts of massive Porites
spp. coral head boulders that had been cast ashore and found that the ages of two boulders correspond to
the 1771 event. One large Porites boulder (diameter > 4 m) was dated to 1625, suggesting that that event
was also a large inundation event. Calibrated 14C ages, based on a newly estimated local value for the
radiocarbon marine reservoir effect, clustered around 1625 and 1771, suggesting that these events were
larger than the others. Our study demonstrated that Porites boulders have enormous potential value for
studies of paleoinundation events such as tsunamis and extreme storms..
24. Suzuki, A., Yokoyama, Y., Kan, H., Minoshima, K., Matsuzaki, H., Hamanaka, N., Kawahata, H., Identification of 1771 Meiwa Tsunami deposits using a combination of radiocarbon dating and oxygen isotope microprofiling of emerged massive Porites boulders, QUATERNARY GEOCHRONOLOGY, 10.1016/j.quageo.2007.12.002, 3, 3, 226-235, 2008.08, The Meiwa Tsunami, one of the largest tsunamis recorded in historical documents in Japan struck Ishigaki Island and neighboring
islands of the Ryukyu Arc in April 1771 AD, killing more than 12 000 people. An enormous number of massive Porites coral boulders are
scattered on the shore and in the reef moat of eastern Ishigaki Island. Although these boulders likely were cast ashore by the Meiwa
Tsunami, a detailed examination has not yet been conducted. When the marine reservoir effect is taken into account, one of mode values
of calibrated radiocarbon dates possibly corresponds to the time of the 1771 event. However, the range of calibrated radiocarbon ages
indicates that the transport of the boulders cannot be ascribed solely to the tsunami. Oxygen isotope microprofiling, which indicates seasurface
temperature variation, was therefore conducted to further investigate the mechanism of transport. The results suggest that the
skeletal growth of most coral colonies was interrupted in summer or autumn; hence, tropical storms and typhoons are also very likely to
be agents of transport. Thus, by combining radiocarbon dating with oxygen isotope microprofiling to investigate Porites coral boulders,
it is possible to separate paleotsunami boulders from those transported by storm events as far as tsunamis occurred during the non-storm
25. Kan, H., Ali, M, Riyaz, M, The 2004 Indian Ocean Tsunami in the Maldives: scale of the disaster and topographic effects on atoll reefs and islands., Atoll Research Bulletin, 554, 1-65, 2007.12, Following the tsunami caused by the Sumatra-Andaman earthquake of 26
December 2004, the Republic of Maldives reported 82 confirmed deaths, 26 people
missing and more than 3,997 incidents of house/building damage. Such an experience
suggests that all atoll nations/districts in the Pacific and Indian Oceans face a potential
risk of severe tsunami-induced damage, and an understanding of what occurred may help
us to form a basis for recognizing the safer areas of land on atoll islands.
To this end, we investigated 43 islands in the northern-to-southern Maldives by
measuring watermarks and profiles across the islands, and interviewing local residents to
determine the characteristics of the tsunami and evacuation procedures.
The movement and influence of the tsunami varied by atoll and island topography.
In the northern Maldives where the atoll rims consist of numerous faroes and are
interrupted by many channels, the tsunami entered the lagoons through these channels
and appeared to set-up the lagoon water level. The backwash of the lagoon water to the
open ocean caused inundation of the lagoon-side villages on islands at the eastern atoll
rim. Beach ridges developed on the eastern side of these islands acted as breakwaters
against the tsunami from the east. In contrast, catastrophic damage and high run-up levels
of 3.6 m above Mean Sea Level (MSL) at maximum water depth occurred on the eastern
islands in atolls with a continuous atoll rim in the southern Maldives. Damage on the
western atoll rims and in the lagoons was relatively small. The continuous eastern atoll
rim and its islands acted as a breakwater against the tsunami from the east. The eastern
islands in atolls in the central Maldives where the atoll rim is moderately interrupted by
channels were hit by both the direct surge from the east and floodwater from the lagoon.
Less damage was reported from the far southern atolls where major channels cut across
the atoll chain.
The movement of the tsunami in atolls thus differed according to the distribution
of the atolls in the archipelago and the continuity of atoll rims against the incoming
direction of the tsunami. The disaster status on individual islands also differed according
to the location of islands on atolls, height of islands, and development of beach ridges
and associated topographic zones.
It is generally understood that the Indian Ocean tsunami arrived without any
forerunning phenomena in areas located west of tsunami source area. However, according
to the results of our interviews in the southern Maldives, the following forerunning
phenomena were in fact observed: 1) loud noises (from 2-to-10 minutes before the
tsunami); 2) bubbling reef flat water (from 2-to-10 minutes before the tsunami); and 3)
the thrusting up of house floors or the bottoms of concrete wells (a few-to-10 seconds
before the maximum tsunami surge). Refuge taken in branched trees and in the lee of
strong walls was especially effective on low-lying atoll islands. Fishing boats (dhonis)
played an important role in the rescue of people swept into lagoons. It is hoped that the
collation of detailed information on the December 2004 tsunami events and disaster
measures taken in this report will contribute to a better understanding of the risks faced
by atoll nations, as well as to risk management development..
26. Kan, H., Kawana, T., ‘Catch-up’ of a high-latitude barrier reef by back-reef growth during the post-glacial sea-level rise, Southern Ryukyus, Japan., Proc. 10th International Coral Reef Symposium, 494-503., 2006.12.
27. Suzuki, A., Gagan, M.K., Kan, H., Siringan, E.A., Yoneda, M., Kawahata, H., Coral records of 1990s in the northwest Pacific: El Niño, coral bleaching, and global warming., Kawahata, H. (ed.) Global Climate Change and Response of Carbon Cycle in the Equatorial Pacific and Indian Oceans and adjacent landmasses. Elsevier Oceanography Series, 73, 217-244., 2006.10.
28. Watanabe, T., Suzuki, A., Kawahata, H., Kan, H., Ogawa, S., A 60-year isotopic record from a mid-Holocene fossil giant clam (Tridacna gigas) in the Ryukyu Islands: physiological and paleoclimatological implications., Palaeogeography Palaeoclimatology Palaeoecology, 212, 343-354., 2004.09.
29. Watanabe, T., Suzuki, A., Kawahata, H., Kan, H., Ogawa, S., A 60-year isotopic record from a mid-Holocene fossil giant clam (Tridacna gigas) in the Ryukyu Islands: physiological and paleoclimatological implications., 2004.09.
30. Inoue, M., Suzuki, A., Nohara, M., Kan, H., Kawahata, H., Coral Skeletal Tin and Copper Concentration at Pohnpei, Micronesia: Possible Index for Marine Pollution by Toxic Anti-biofouling Paints. , Environmental Pollution, Vol.129, p.399-407., 2004.06.
31. Fall, O., Hori, N., Kan, H., Diop, M., Toward an integrated management plan of the Djoudi Park water resources: Senegal River mouth., Environmental Management, Vol.31, p.14-28., 2003.01.
32. Kawana, T., Kan, H., Matsumoto, E., Holocene coral reefs at Gushichan coast in the southern Okinawa Island, the Ryukyus, Japan, as deduced from drilling cores., Matsumoto,E. (ed.) Coral climatology by annual bands, Proc. 3rd International Marine Science Symposium, p.58-63., 1998.03.
33. Kan, H., Hori, N., Kawana, T., Kaigara, T., Ichikawa, K., The evolution of a Holocene fringing reef and island: reefal environmental sequence and sea level change in Tonaki Island, the central Ryukyus., Atoll Research Bulletin, No.443, p.1-20., 1997.10.
34. Kan, H., Nakashima, Y., Hopley, D., Coral communities during structural development of a fringing reef flat, Hayman Island, the Great Barrier Reef., Proc. 8th International Coral Reef Symp., Vol.1, p.465-470., 1997.06.
35. Kan, H., Hori, N., Ichikawa, K., Formation of a coral reef-front spur, CORAL REEFS, 16, 1, 3-4, 1997.02.
36. Kan, H., Hori, N., Nakashima, Y., Ichikawa, K., The evolution of narrow reef flats at high-latitude in the Ryukyu Islands. , Coral Reefs, Vol.14, p.123-130., 1995.09.
37. Kan, H., Typhoon effects on sediment movement on reef edges and reef slopes., Bellwood,O. et al. (eds.) Recent advances in marine science and technology '94. Pacon International and James Cook Univ., Townsville, p.191-201., 1995.06.
38. Kan, H., Hori, N., Topographic formation on the well-developed fringing reef-flat, Minna Island, the central Ryukyus., Transactions Japanese Geomorphological Union, Vol.14. No.1, p.1-16., 1993.01.
39. Kan, H., Takahashi, T., Koba, M., Morpho-dynamics on Holocene reef accretion: drilling results from Nishimezaki Reef, Kume Island, the Central Ryukyus., Geographical Review of Japan, Vol.64 (Ser.B), No.2, p.114-131., 1991.12.
40. Kan, H., Hori, N., Methodology and conceptual design for geomorphological surveying of submarine 'road cut' in modern reef-flats. , Geographical Sciences, Vol.46, No.3, p.208-221., 1991.09.
41. Takahashi, T., Koba, M., Kan, H., Relationship between reef growth and sea level on the northwest coast of Kume Island, The Ryukyus: data from drill holes on the Holocene coral reef., Proceedings of the 6th International Coral Reef Symposium, Vol.3, p.491-496., 1988.12.
42. Koba, M., Tamura, M., Ikeya, M., Miki, T., Kaigara, T., Nakashima, Y., Kan, H., Quaternary shorelines and crustal movements on Minamidaito-Jima, northwestern Pacific., Yunshan, Q. and Songling, Z. (eds.), Late Quaternary Sea-Level Change, China Ocean Press, p.188-198., 1986.12.