Paleotsunami researches along the Ryukyu Trench

Abstract

Paleotsunami research along the Ryukyu Trench has been undertaken for ca. 50 years. In particular, studies of tsunami-transported boulders have shown that large tsunamis have repeatedly occurred in the Sakishima Islands along the southern Ryukyu Trench, whereas no large tsunamis have affected the Amami and Okinawa islands along the northern and central Ryukyu Trench in the past 2300 yr. These observations are supported by seismological research and imply that earthquakes and tsunamis occur unevenly along the Ryukyu Trench. In contrast to studies of tsunami-transported boulders, sandy and gravely deposits related to tsunamis have been less extensively studied. Future research on such sandy deposits is expected to reveal more detailed paleotsunami histories, which include small- to moderate-scale events.