抄録
On the basis of a distribution of Recent reef blocks scattered on Tarama Island, the southern Ryukyu Islands, a behavior and a run-up height of Yaeyama Seismic Tsunami (1771) which swept over the Island from SW can be inferred. There are many reef blocks in Tarama Island and they fall into two kinds : Recent reef blocks and Pleistocene Ryukyu Limestone blocks. From the distribution of the latter the movement of the tsunami cannot be inferred. However, as all Recent reef blocks on the Island are considered to have been thrown on the land by the tsunami, it can be inferred how the tsunami took place. Based on the fact aragonites, components of coral fossils in Recent reef blocks, are not inverted to calcite, the Recent reef blocks can be distinguished from the Ryukyu Limestone blocks. As a result of an examination of the distribution of Recent reef blocks and the topography of the sea floor and Tarama Island, it has been inferred that there were five northheaded strong branches of the tsunami on the Island. Western two branches ran across the Island and pushed many blocks to the north shore of the Island. The central strong branch moved many blocks from the sea area to the land or within the inland towards northward. This was the very branch that threw some Recent coral blocks over to 17m above the sea level, the highest level of the places where the blocks were thrown over. On the basis of altitude and height of the block, the highest run-up height of the tsumani at the Island was inferred to be a little higher than 18m.
