[M-IS12] tsunami deposit

[MIS12-02] Before and after relationship between the seismic uplift and the large tsunami due to the seventeenth-century giant earthquake observed in the seismic barrier systems around the Kuril subduction zone

*Futoshi Nanayama^1,5, Kazuaki Watanabe¹, Keita Fukatsu², Takeshi Hasegawa⁴, Kiyoyuki Shigeno³, Masayuki Ishii⁶, Kazuhito Ishiwata⁷, Shigeto Inokuma⁸ (1.Geological Survey of Japan, AIST, 2.Notsuke Peninsula Nature Center, 3.Meiji consultant Co., Ltd., 4.Ibaraki University, 5.CWMD, Kumamoto Univ., 6.Ishii Professional Engineer Office, 7.Betsukai municipal museum, 8.Nemuro City museum history and nature)

Keywords:Seventeenth-century giant earthquake, Tsunami, Regional crustal movement, Barrier system, eastern Hokkaido, Kuril subduction zone

The Kuril subduction zone is one of the most frequent earthquakes in Japan. There are many undeveloped plains in this area, unspoiled nature is left, and many barrier coasts and tsunami deposits due to the giant earthquake (17th century type) repeatedly generated at 400 to 500 years intervals can be widely observed around this area. However, the relationship between the timing of both is not clear yet. Especially two tsunami deposits, which are occurred in the 17th century, can be observed in many places around the eastern Pacific coast of Hokkaido. On the other hand, there are many active barrier systems around the coast of Nemuro Strait and Konsen ~ Tokachi coast, and it has recently become evident that a 17th century giant earthquake occurred as a trigger. Our research group examined the relationship between the occurence timing of these uprifting barrier systems and the 17th century tsunami in several areas in detail, and some interesting facts have been found, so we will report the outline in this meeting.

This work was supported by JSPS KAKENHI Grant Number 18K03767.