Distribution of Coral Boulders Beached by Huge Tsunamis and Calibrated Radiocarbon Ages of Fossil Porites sp. of Maibahbama, SE of Miyako Island, Okinawa Prefecture

Abstract

 A large number of coral boulders are scattered on reef flats and along the shores of Sakishima Islands, SW of Japan. Many were considered to have been cast ashore by huge tsunamis. In this report the author analyzes the distribution and calibrates the ¹⁴C ages of coral boulders collected from Maibahbama, southeast of Miyako Island. The calibrated ¹⁴C ages indicate a random distribution; however, some coincided exactly with the 1771 Meiwa tsunami. The tsunami travelled from the epicenter northeast and struck the Higashihenna Promontory, then turned westward leaving a large numbers of coral boulders on Maibahbama. Judging from tsunami deposits overlaying the lowest marine terrace the wave height seems not to have exceeded 10m.