[M-IS11] tsunami deposit

[MIS11-07] Event deposits at the coastal plain of the North Kyushu to Yamaguchi area in the Sea of Japan

*Atsushi Urabe¹, Yoshiya Kobayashi², Shinji Hamasaki² (1.Research Institute for Natural Hazards and Disaster Recovery, Niigata University, 2.Board of education, Shimonoseki City)

Keywords:event deposit, North Kyushu and Ymaguchi, Sea of Japan

The region from the North Kyushu to the Yamaguchi area in the Sea of Japan is estimated to be a source of tsunamis. However, there are only a few records on the history of tsunamis. This report summarizes tsunami sediment investigations in Shimonoseki, Yamaguchi and Iki, and Nagasaki.
Based on topography and an existing report, coring explorations were carried out at 11 sites in the Ayaragi River region and 6 sites in the Kajikuri River region near Shimonoseki. Two event sand layers estimated to be approximately 2,500 and 3,500 years old were found in the silty layer of the flood plain. In the Doigahama region near Shimonoseki, coring explorations were carried out at 16 sites; two event sand layers estimated to be between 2,500–2,700 and 3,500 years old (approximately) were found in the peaty silt layer from the flood plain to the marsh. Cores from the Ashibe district in the eastern part of Iki Island revealed event sediment 3,500 year old sediment from a silty bay.
These investigations revealed the presence of sediments from events that occurred approximately 2,500 and 3,500 years ago in the area from the coast of North Kyushu to the Yamaguchi area in the Sea of Japan.