マルチビーム測深調査とスクーバ潜水調査によるサンゴ礁および浅海域地形学の研究
キーワード：サンゴ礁，沈水カルスト，浅海底，地形学，マルチビーム測深機，スクーバ潜水
2014.06～2023.03.

沿岸浅海域の地理学研究：浅海底地形学の構築および海底景観の可視化と啓発
2021.04～2025.03, 代表者：菅　浩伸, 九州大学, 日本学術振興会.

浅海底地形学を基にした沿岸域の先進的学際研究 －三次元海底地形で開くパラダイム－
2016.06～2021.03, 代表者：菅　浩伸, 九州大学, 日本学術振興会.

マルチビーム測深技術を用いた浅海底地形学の開拓と防災・環境科学への応用
2013.04～2017.03, 代表者：菅　浩伸, 九州大学　比較社会文化研究院, 日本学術振興会
本研究は熱帯・亜熱帯島嶼のサンゴ礁地形および堆積構造を，防災構造および環境や文化を支える地形として評価することを目指した研究である。本研究では，最先端のマルチビーム測深を用いて作成する精密海底地形図を基に，これまでの知見がきわめて少なかった浅海底の地形とその形成について議論を行い，従来の地形学にない「浅海底地形学」を開拓する端緒となる研究へと発展させることを目指す。まずサンゴ礁の地形を平成22年度に導入したワイドバンドマルチビーム測深機を用いて可視化する。特に波浪を減衰する礁縁部から上部礁斜面の地形についての高解像度三次元図を提示する。可視化した沿岸域の地形を「防災基盤」として評価し，台風・高潮災害の増大と津波のリスクに対して効果的な地形の分布を明らかにする。また，人の生活圏に近く海域利用が盛んである沿岸の海底地形を「環境や文化を支える地形」として捉え，作成した精密海底地形図を，健全な生態系と里海文化の継承につながる研究のためのベースマップとして利用する試みを行う。これらを通して，「浅海域」を鍵とした自然科学から社会・文化科学の領域にわたる学際研究へと発展させることを目指す。
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主要著書

1.	菅 浩伸, フォトグラメトリの利用―エモンズ号の調査. 『水中遺跡ハンドブック』, 文化庁文化財第二課, 文化庁文化財第二課, 143, 2022.03.
2.	菅 浩伸, マルチビーム測深でつくる大縮尺海底地形図. 木村淳, 小野林太郎編著 『図説 世界の水中遺跡』, グラフィック社, グラフィック社, 96-97, 2022.02.
3.	菅 浩伸, モルディブ概観 第２章　サンゴ礁とサンゴ洲島―独特なサンゴ礁地形をつくるインド洋の気候. 新井悦代・今泉慎也編 『モルディブを知るための３５章』, 明石書店, 明石書店, 22-29, 2021.12.
4.	菅 浩伸, 沖縄貝塚時代人がみたサンゴ礁. 青山和夫, 米延仁志, 坂井正人, 高宮広土編 『文明の盛衰と環境変動』, 岩波書店, 岩波書店, 208-209, 2014.09.
5.	菅 浩伸, サンゴ礁景観の成り立ちを探る. 小泉武栄，赤坂憲雄編 『自然景観の成り立ちを探る』, 玉川大学出版部, p.222-235., 2013.10.
6.	菅 浩伸, サンゴ礁形成研究の歴史と展望. 中森　亨編 『日本に於けるサンゴ礁研究Ⅰ』, 日本サンゴ礁学会, p.79-85., 2002.01.
7.	菅 浩伸, 南西諸島を縁どるサンゴ礁海岸.　米倉伸之，貝塚爽平，野上道男，鎮西清高編 『日本の地形１　総説』 7-5章 (3), 東京大学出版会, p255-258., 2001.03.
8.	菅 浩伸, 琉球列島のサンゴ礁形成過程. 高宮広土，新里貴之編『琉球列島先史・原始時代の環境と文化の変遷』, 琉球列島先史・原始時代における環境と文化の変遷に関する実証的研究 研究論文集 第2集, 六一書房, p.19-28., 2014.03.
9.	Webster, J., Yokoyama, Y., Cotterill, C., Kan, H., et al., Integrated Ocean Drilling Program Expedition 325 Preliminary Report Great Barrier Reef environmental changes The last deglacial sea level rise in the South Pacific: offshore drilling northeast Australia., Integrated Ocean Drilling Program Management International, Inc., 479pp, 2010.12.
10.	菅 浩伸, モルディブ諸島にみる環礁立国崩壊の危険性 －災害と開発の連鎖－. 日本地理学会災害対応委員会・平井幸弘・青木賢人編 『温暖化と自然災害－世界の六つの現場から』, 古今書院, p.59-84., 2009.09.
11.	Kan, H., Ryukyu Islands. In: Hopley, D. (ed.) Encyclopedia of Modern Coral Reefs: structure, form and process, Springer, Encyclopedia of Earth Science Series, p.940-945., 2011.01.

主要原著論文

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, https://doi.org/10.1080/10572414.2021.2018870, 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, https://doi.org/10.1016/j.epsl.2021.117354, Volume 579, Article 117354, 2022.02.
3.	菅　浩伸，木村　颯，佐野　亘，三納正美, 玄武岩海食崖沖の海食台, 地形, 42, 3, 69-81, 2022.01.
4.	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, https://doi.org/10.1038/s41598-020-64100-6, 2020.04.
5.	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, https://doi.org/10.1130/G46792.1, 48, 1, 39-43, 2020.01.
6.	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, https://doi.org/10.1016/j.gloplacha.2018.12.014, 174, 70-91, 2019.03.
7.	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, https://doi.org/10.1016/j.palaeo.2018.10.033, 514, 386-397, 2019.01.
8.	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, https://doi.org/10.1038/s41586-018-0335-4, 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..
9.	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..
10.	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, https://doi.org/10.1038/s41561-018-0127-3, 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..
11.	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, https://doi.org/10.1016/j.quaint.2017.09.032, 471, 359-368, 2018.04.
12.	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..
13.	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..
14.	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..
15.	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..
16.	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..
17.	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..
18.	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 worldwide..
19.	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 greatest..
20.	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..
21.	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 season..
22.	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..
23.	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.
24.	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.
25.	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.
26.	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.
27.	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.
28.	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.
29.	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.
30.	Kan, H., Hori, N., Ichikawa, K., Formation of a coral reef-front spur, CORAL REEFS, 16, 1, 3-4, 1997.02.
31.	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.
32.	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.

主要総説, 論評, 解説, 書評, 報告書等

1.	菅　浩伸, 黒潮かつくったサンゴの楽園：沖縄., 科学, Vol.88, No.6, p.582-587., 2018.06.
2.	菅　浩伸, 人類のフロンティア「浅海底」を開拓する., 科学，Vol.84, No.12, p.1213-1215., 2016.12.

主要学会発表等

1.	伊藤真裕子, 清島璃乃, 菅 浩伸, 宮入陽介, 横山祐典, 藤田和彦, 堆積物特性と放射性炭素年代に基づく久米島ハテノハマ周辺サンゴ礁堆積物の生産・運搬・堆積, 日本地球惑星科学連合2018年大会, 2018.05.
2.	田中 圭, 濱 侃, 菅 浩伸, 長谷川 均, マルチプラットフォームリモートセンシングに基づく洲島の形状変化モニタリング, 日本地球惑星科学連合2018年大会, 2018.05.
3.	Kan, H., Katagiri, C., Nakanishi, Y., Yoshizaki, S., Nagao, M,, Ono, R., High-resolution seafloor DEM of World War II wreck site by combining multibeam bathymetry and SfM photogrammetry, 日本地球惑星科学連合2018年大会, 2018.05.
4.	菅　浩伸，藤田和彦，横山祐典，浦田健作，中島洋典，堀　信行，長尾正之，羽佐田葉子，Frederic SINNIGER, 宮入陽介，石沢成美，岩田良哉，大城夏生, 湿潤熱帯域の浅海底地形学：石垣島名蔵湾の沈水カルスト地形の発達, 2018年日本地理学会春季学術大会, 2018.03.
5.	鈴木　淳，酒井一彦，林　正裕，山本雄三，太田雄貴，井口　亮，井上麻夕里，菅　浩伸，野尻幸宏, 海洋酸性化現象が浅海の付着生物の加入定着に与える影響評価実験, 日本海洋学会秋季大会, 2017.10.
6.	Kan, H., Fujita, K., Hasegawa, H., Nagao, M., Nakashima, Y., Hori, N., Multibeam Bathymetric Mapping of Reef Geomorphology, eastern Kume Island, Japan-Australia Sangosho Geomorphology (JASAG) Workshop 2017, 2017.09.
7.	Kan, H., High-resolution Bathymetric Mapping Project for coral reef geomorphology and related sciences in the Ryukyu Islands, Japan, Japan-Australia Sangosho Geomorphology (JASAG) Symposium 2017, 2017.09.
8.	Toguchi, K., Fujita, Y., Nakai, T., Hasegawa, H., Takahashi, S., Kan, H., Bio-geomorphological evaluation of the depression “Katama” located in the reef edge as a fishery ground, Japan-Australia Sangosho Geomorphology (JASAG) Symposium 2017, 2017.09.
9.	Ana Vila-Concejo , Stephanie Duce, Masayuki Nagao , Yosuke Nakashima , Mayuko Ito , Kazuhiko Fujita and Hironobu Kan, Typhoon waves on coral reefs, Coastal Dynamics 2017, 2017.06.
10.	菅 浩伸, 長尾正之, 片桐千亜紀, 吉崎　伸, 中西裕見子, 小野林太郎, マルチビーム測深と多視点ステレオ写真測量(SfM)を組み合わせた海底の精密三次元モデル構築：水中戦争遺跡とサンゴ礁地形を例として, 2017年日本地理学会春季学術大会, 2017.03.
11.	Sinniger, F., Prasetia, R., Kan, H., Harii, S., Are deep reefs really refuges during massive bleaching events?, 日本サンゴ礁学会19回大会, 2016.12.
12.	Kan, H., Katagiri, C., Ono, R., Nagao, M., Nakanishi, Y., Yoshizaki, Y., 3D visualization of USS Emmons (WWII wreck) off Okinawa Island using multibeam bathymetry and PhotoScan SfM software, The Sixth International Congress on Underwater Archaeology, 2016.11.
13.	Kan, H., Fujita, K., Yokoyama Y., Suzuki, A., Miyairi, Y., Webster, J.M., Carbonate cement as an indicator of sea level during the last glacial period: IODP Exp. 325, Great Barrier Reef Environmental Changes, Goldschmidt 2016, 2016.06.
14.	Kan, H., Fujita, K., Hasegawa, H., Nagao, M., Nakashima, Y., Hori, N., High-energy window in modern reefs: an example from multibeam bathymetric mapping of reef geomorphology around the Ryukyu Islands, 13th International Coral Reef Symposium, 2016.06.
15.	Fujita, K., Yagioka, N., Nakada, C., Kan, H., Yokoyama, Y., Webster, J., Back-reef developments during MIS2 sea-level falls: IODP Expedition 325, Great Barrier Reef, 13th International Coral Reef Symposium, 2016.06.
16.	Webster, J.M., Braga, J.C., Humblet, M., Pottd. D.C., Iryu, Y., Yokoyama, Y., Fujita, K., Bourillot, R., Esat, T., Fallon, S., Thompson, W.G., Thomas, A.L., Kan, H., McGregor, H.V., Hinestrosa, G., The evolution of the Great Barrier Reef over thepast 30 ka – new insights from IODP Expedition 325, 13th International Coral Reef Symposium, 2016.06.
17.	Kan, H., Nagao, M, Fujita, K., Hasegawa, H., Nakashima, Y., Hori, N., High-resolution multibeam bathymetric mapping of barrier reef geomorphology of eastern Kume Island, the Ryukyus, 日本地球惑星科学連合2016年大会, H-GM01　Geomorphology（国際セッション）, 2016.05.
18.	菅 浩伸, 太平洋・インド洋の環礁国における土地利用と国土の脆弱性, 日本地球惑星科学連合2016年大会, セッションH-CG27環境問題の現場におけるScientistsとStakeholdersとの協働, 2016.05.
19.	菅 浩伸, 長谷川均, 藤田和彦, 長尾正之, 中島洋典, 堀　信行, 久米島東岸の堡礁地形：マルチビーム測深と潜水調査を基にした海底地形学, 2016年日本地理学会春季学術大, 2016.03.
20.	Kan, H., Fujita, K., Yokoyama, Y., Suzuki, A., Miyairi, Y., Webster, J., Shallow-water submarine cement observed from the shelf edge of the Great Barrier Reef, XIX INQUA (International Union for Quaternary Research) 2015, 2015.07.
21.	Fujita, K., Yagioka, N., Nakada, N., Miyairi, Y., Yokoyama, Y., Kan, H., Webster, J., Sea-level fluctuations from late MIS3 to MIS2, inferred from large benthic foraminiferal assemblages: IODP Exp. 325, Great Barrier Reef Environmental Changes, XIX INQUA (International Union for Quaternary Research) 2015, 2015.07.
22.	Yokoyama, Y., Esat, T.M., Thompson, W.G., Thomas, A.L., Webster, J., Miyairi, Y., Sawada, C., Aze, T., Matsuzaki, H., Okuno, J., Fallon, S., Braga, J.C., Humblet, M., Iryu, Y., Potts, D.C., Fujita, K., Suzuki, A., Kan, H., Sea level record obtained from submerged the Great Barrier Reef coral reefs for the last 30 ka, XIX INQUA (International Union for Quaternary Research) 2015, 2015.07.
23.	Webster, J., 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., Response of the Great Barrier Reef to sea level and environmental changes over the past 30 ka, XIX INQUA (International Union for Quaternary Research) 2015, 2015.07.
24.	Miklavič, B., Urata, K., Yokoyama, Y., Miyairi, Y., Kano, A., Kan, H., Phreatic cave deposits on Minami Daito – high precision indicators of Holocene sea-level change in the Northern Philippine Sea, XIX INQUA (International Union for Quaternary Research) 2015, 2015.07.
25.	Kan, H., Nagao, M., Toguchi, K., Hori, N., Urata, K., Fujita, K., Yokoyama, Y., Nakashima, Y., Hasegawa, H., Nakai, T., Goto, K., Katagiri, C., Ono, R., Sinniger, F., Prasetia, R., Harii, S., Iguchi, A., Suzuki, A., High-resolution multibeam bathymetric survey for coastal seafloor geomorphology and related sciences, 日本地球惑星科学連合2015年大会, 2015.05, The geomorphology of shallow coastal regions has been modulated by repeated subaerial and submarine processes during glacio-eustatic sea-level change. However, in contrast to the vast knowledge that has been accumulated regarding terrestrial landforms, few previous studies have dealt with shallow seafloor landforms, which represent former terrestrial landscapes modified by present marine processes, from a geomorphological perspective.A broadband multibeam echosounder (Sonic 2022, R2 Sonic, LLC) and its accessory system were introduced to H. Kan’s laboratory in 2010 using JSPS Grant-in-Aid for Scientific Research A. We have carried out our bathymetric survey in Kume, Ishigaki, Kikai Islands and the southeastern and northwestern coasts of Okinawa Island in the Ryukyus, southwestern Japan since 2010.The Sonic 2022 has a variable ultrasonic frequency of 200 to 400 kHz, 256 ultrasonic beams and selectable swath coverage of 10 to 160 degrees. The typical ultrasonic beam widths parallel and orthogonal to the direction of travel are within one degree of each other when an ultrasonic frequency of 400 kHz is selected. We used a VS111 GPS compass system with A20 and A30 antennas (Hemisphere Inc.) combined with a dynamic motion sensor (DMS-10, Teledyne TSS Ltd.), a sea surface sound velocity sensor (miniSVS, Valeport Ltd.), a sound velocity profiler (MicroSVP, AML Oceanographic Ltd.). Overlap of at least ~20% (typically ~50%) was implemented throughout the bathymetric survey to ensure 100% coverage of the surveyed area. The minimum and maximum depth was 1m and 400m, respectively. The HYPACK2010 software was used for both hydrographic survey and data processing. IVS3D Fledermaus was used for three-dimensional visualization. We conducted geomorphological studies of the coastal seafloor in the coral reef areas of the Ryukyu Islands based on our high-resolution bathymetric map with a grid size of 1 m combined with SCUBA diving observations. For example, the submerged tropical karst features were discovered in Nagura Bay, Ishigaki Island (Kan et al. 2015). This is the first description of submerged humid tropical karst using multibeam bathymetry. Along with the geomorphological studies, we have also started biological and archeological studies in our bathymetric areas to promote interdisciplinary researches which link natural and human sciences..
26.	菅 浩伸, Sinniger, F., Prasetia, R., 波利井佐紀, 藤田和彦, 浦田健作, 長尾正之, 中島洋典, 堀　信行, 佐伯信雄, 石垣島名蔵湾の沈水カルスト域における独特かつ未知のサンゴ礁地生態系, 2015年日本地理学会春季学術大, 2015.03.
27.	Kan, H., Urata, K., Nagao, M., Hori, N., Fujita, K., Yokoyama, Y., Nakashima, Y., Ohashi, T., Goto, K., Suzuki, A., Submerged humid tropical karst landforms observed by high-resolution multibeam survey in Nagura Bay, Ishigaki Island, southwestern Japan, American Geophysical Union 2014 Fall Meeting, 2014.12, Submerged tropical karst features were discovered in Nagura Bay on Ishigaki Island in the South Ryukyu Islands, Japan. This is the first description of submerged humid tropical karst using multibeam bathymetry. 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 with a grid size of 1 m 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. We assume that Nagura Bay was a large karst basin in which older limestone remained submerged, thus preventing corrosion and the accumulation of reef sediments during periods of submersion, whereas the limestone outcropping on land was corroded during multiple interglacial and glacial periods. Based on our bathymetric result together with aerial photographs of the coastal area, we conclude that the submerged karst landscape has likely developed throughout the whole of Nagura Bay, covering an area of ~6 × 5 km. Accordingly, this area hosts the largest submerged karst in Japan. We also observed abundant coral communities during our SCUBA observations. The present marine conditions of Nagura Bay are characterized by low energy (calm sea) and low irradiance owing to the terrestrial influence. Such conditions have been emphasized by the presence of large undulating landforms, which cause decreases in wave intensity and irradiance with depth. These characteristics have acted to establish unique conditions compared to other coral reef areas in the Ryukyu Islands. It may play an important role in supporting the regional coral reef ecosystem. .
28.	菅 浩伸, Sinniger, F., Prasetia, R.., 波利井佐紀, 佐伯信雄, 長尾正之, 浦田健作, 石垣島・名蔵湾の沈水カルスト地形とサンゴ群集, 日本サンゴ礁学会 第17回大会, 2014.11.

所属学会名

学協会役員等への就任

学会大会・会議・シンポジウム等における役割

学会誌・雑誌・著書の編集への参加状況

学術論文等の審査

海外渡航状況, 海外での教育研究歴

外国人研究者等の受入れ状況