17:15 〜 18:45
[U15-P86] 2024年能登半島地震に伴う富山深海長谷への堆積物輸送
キーワード：2024年能登半島地震、富山深海長谷、炭素窒素安定同位体比
On January 1, 2024, a magnitude (Mw) 7.5 Noto Peninsula earthquake struck at a depth of 15.5 km north of the peninsula. Tsunami waves were observed along the coasts of the Sea of Japan, including South Korea and Russia. Instrumentally observed tsunami heights ranged from 0.4 m to over 1.2 m at Wajima Port, causing damage to the coastal areas. A significant landslide occurred within Toyama Bay, confirmed to have collapsed over a width of 1.1 km and a depth of 50 m. While there is a possibility of sediment movement from shallow to deep sea due to the collapsed slope and tsunami backwash, information regarding seafloor changes caused by the earthquake remains scarce.
In our laboratory, surface sediment samples have been collected annually from the Toyama Deep-Sea Channel (TDSC) since 2021. These samples have been analyzed for organic carbon and nitrogen stable isotope ratios, elemental concentrations, and grain size measurements. It indicates that the uppermost sediment in the TDSC is composed of coarse sandy silt and contains abundant land-derived organic carbon. Furthermore, elemental concentrations suggest a significant influence of sediment from the Hime and Kurobe River basins, indicated by higher Ni and Cr concentrations in the northern TDSC and K concentrations in the southern part.
Therefore R/V Hakuho-Maru KH-24-E1 cruise was carried out to collect surface sediment from the TDSC. The layer of clay with no trace fossil above the sand layers observed from the uppermost part of two multiple core samples, was not found in the core collected in May 2023 within the TDSC around the study area. Furthermore, chemical tracers (major and trace elements, carbon and nitrogen stable isotope etc.) will be measured to evaluate the origin of the sediment. Additionally, 137Cs and 210Pbex will also be analyzed to determine sedimentation chronologies. Finally, these data will be compared to the pre-earthquake data around the TDSC to constrain the sediment source.
In our laboratory, surface sediment samples have been collected annually from the Toyama Deep-Sea Channel (TDSC) since 2021. These samples have been analyzed for organic carbon and nitrogen stable isotope ratios, elemental concentrations, and grain size measurements. It indicates that the uppermost sediment in the TDSC is composed of coarse sandy silt and contains abundant land-derived organic carbon. Furthermore, elemental concentrations suggest a significant influence of sediment from the Hime and Kurobe River basins, indicated by higher Ni and Cr concentrations in the northern TDSC and K concentrations in the southern part.
Therefore R/V Hakuho-Maru KH-24-E1 cruise was carried out to collect surface sediment from the TDSC. The layer of clay with no trace fossil above the sand layers observed from the uppermost part of two multiple core samples, was not found in the core collected in May 2023 within the TDSC around the study area. Furthermore, chemical tracers (major and trace elements, carbon and nitrogen stable isotope etc.) will be measured to evaluate the origin of the sediment. Additionally, 137Cs and 210Pbex will also be analyzed to determine sedimentation chronologies. Finally, these data will be compared to the pre-earthquake data around the TDSC to constrain the sediment source.