Estimation for a transport agent of historical tsunamis from huge boulders on a marine terrace

2016 Fiscal Year Final Research Report

• Project/Area Number: 25350430
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Geography
• Research Institution: Tokyo Gakugei University (2014-2016); Daito Bunka University (2013)
• Principal Investigator: Aoki Hisashi 東京学芸大学, 教育学部, 准教授 (30423742)
• Project Period (FY): 2013-04-01 – 2017-03-31
• Keywords: 津波 / 津波石 / 海食崖 / 海岸段丘 / 琉球列島 / 宮古島 / 石垣島

Outline of Final Research Achievements

Mega-boulders are found on a marine terrace along the shores of the Miyako and the Yaeyama Islands, both located in the western part of the Ryukyu Islands. The boulders are thought to have been transported onto the marine terrace by the action of historical tsunamis ever assaulted these islands. To estimate the transport ability of such tsunamis, this study investigated the weight (W) of boulders and the relative height (H) of a steep cliff at the seaward edge of the marine terrace. It is found that the quantity WH is available for a useful index for representing tsunami energy. The maximum value of WH at the study site of the Miyako Islands is higher than that of the Yaeyama Islands. This suggests that a transport agent of tsunamis hit the Miyako Islands was larger, which is different from the previous view that the 1771 Meiwa tsunami attacked Ishigaki Island, one of the Yaeyama Islands, had the largest agent in the Ryukyu Islands.

Free Research Field

地形学