Study on disaster protection function of coral reefs and maintenance of structure for reef-island system in atoll nations

本研究旨在观察环礁国家可持续发展的前景。对印度洋马尔代夫的环礁岛对海啸的反应、基岩地质和地形进行了调查，并对太平洋环礁岛国家（马绍尔群岛共和国、基里巴斯和图瓦卢）进行了地形调查。我们观察到环礁和珊瑚岛的结构强度与岛屿基础设施对海啸的脆弱性形成对比。我们还观察到马尔代夫共和国首都马累的一堵礁墙在水下大规模坍塌。我们的研究结果指出了全新世海底胶结礁的硬地质结构对环礁岛基底地质的重要性，以及在世界上人口严重过剩的珊瑚礁城市中可能普遍存在的地质灾害风险。

This study aims to observe prospects for sustainable development of atoll nations. Surveys were conducted for atoll islands on the response against tsunami, substrate geology and topography in Maldives in the Indian Ocean along with the topographic surveys in atoll nations in the Pacific (Republic of Marshall Islands, Kiribati and Tuvalu). We observed the structural strength of atoll and coral islands in contrast to the vulnerability of infrastructures on islands against tsunami. We also observed a large-scale underwater collapse of a reef wall at Male, the capital city of the Republic of Maldives. Our findings point out the importance of hard geological structure of Holocene reef with submarine cementation for substrate geology for atoll islands, and also a geohazard risk that may be common in seriously overpopulated coral cay cities around the world.