日本地球惑星科学連合2024年大会

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セッション記号 M (領域外・複数領域) » M-GI 地球科学一般・情報地球科学

[M-GI25] Holocene paleoenvironment, paleoclimate, and paleohazards in the Pacific Islands

2024年5月28日(火) 15:30 〜 16:45 303 (幕張メッセ国際会議場)

コンビーナ:後藤 和久(東京大学大学院理学系研究科)、Goff James(University of New South Wales)、山崎 敦子(名古屋大学大学院環境学研究科)、市原 美恵(東京大学地震研究所)、座長:市原 美恵(東京大学地震研究所)、山崎 敦子(名古屋大学大学院環境学研究科)


16:30 〜 16:45

[MGI25-09] In search of paleotsunami deposits on Viti Levu Island, Fiji

*後藤 和久1ゴフ ジェームス2、マロダリ ジョジ3、クマー ニレシュ4石澤 尭史5笠井 克己1中田 光紀1 (1.東京大学大学院理学系研究科、2.ニューサウスウェールズ大学、3.鉱物資源局、4.南太平洋大学、5.東北大学)

Fiji is located in the central part of the South Pacific. Although there is no tsunamigenic subduction zone close to Fijian islands, Fiji has potential to be affected by large distant tsunamis generated along remote subduction zones such as Tonga Trench and large submarine volcanic eruptions like the 2022 Hunga Tonga-Hunga Haʻapai (HT-HH) event. Also, there is a risk of tsunamis generated by local submarine landslides (Lau et al., 2018). Notwithstanding the high tsunami risks, paleotsunami research in Fiji is scarce (Goff et al., 2020). In this study, we carried out preliminary site surveys on Viti Levu Island to explore its paleotsunami history. Generally, the southern coast of the island is a wave-dominated coast with coral reefs while the northern coastline is dry, with calm conditions and tide-dominated deltas with mangrove forests developed along the coast. As a result of such settings, terrestrial sediments along the northern coastline are generally dry with limited preservation potential for high-energy event deposits. Southern coasts on the other hand have higher potential to preserve such event deposits, although there are few coastal plains. For instance, we found multiple sandy event deposits in the wetlands landward of the Kiuva beach dunes, where the pumice, possibly including the 2022 HT-HH, is scattered over the beach surface. Some of these event deposits, which should be older than the 2022 HT-HH event, contain large pumice fragments. In a similar manner, some sand layers and coral boulders, both of which can be interpreted as event deposits, are also observed along the southwestern coast of the island. Although further analyses are required to identify the origin of these deposits, Viti Levu Island appears to be an important target to study the paleotsunami history of Fiji.

Acknowledgments: This research was supported by SATREPS, JST/JICA and JSPS.