[U-15] The 2024 Noto Peninsula Earthquake (1:J)

[U15-P85] Sediment core samples possibly record 2024 Noto Peninsula Earthquake and past large earthquakes along the Toyama Deep-sea Channel

*Rina Fukuchi¹, Asuka Yamaguchi², Shimpei Ohtsuka³, JING ZHANG³, Yoichi Usui⁴, Atsushi Matsuoka⁵, Jumpei Yoshioka⁶, Takuya Sagawa⁴, Masafumi MURAYAMA⁷, Chiori Tamura², Seitaro Ono², Kyoko Okino², Jin-Oh Park², KH-24-E1cruise menber (1.Naruto university of Education, 2.Atmosphere and Ocean Research Institute, The University of Tokyo , 3.University of Toyama, 4.Kanazawa University, 5.Niigata University, 6.National Institute of Advanced Industrial Science and Technology (AIST), 7.Kochi University)

Keywords:2024 Noto Peninsula Earthquake, KH-24-E1 cruise, Piston core samples, Multiple core samples

The 2024 Noto Peninsula Earthquake on January 1, 2024, occurred along seafloor active faults extending from the northern part of the Noto Peninsula to the waters west of Sado Island, resulting in widespread tsunamis along the Japan Sea coast and uplifts of up to 4 meters in the northern part of the Noto Peninsula. Additionally, several slope failures occurred within Toyama Bay, leading to seafloor mass movements, and potentially causing the early arrival of tsunamis within the Bay. From the coastal area off Cape Suzu to the continental shelf slope, sediments transported from the land by a rip current of the tsunami are expected to be distributed on the seafloor surface. In addition, sediments from the eastern Noto Peninsula and Toyama Bay are likely to be transported via the Toyama Deep-sea Channel to the Japan Basin eventually.
To evaluate the volume and process of sediment transport associated with the tsunami and the turbidite downflow via the Toyama Deep-sea Channel from shallow to deep portion during the 2024 Noto Peninsula Earthquake, we conducted sediment sampling by using piston corers and multiple corers during the research cruise KH-24-E1, carried out by R/V Hakuho-maru from March 4 to 16, 2024.
As a result, layers of olive black, soupy silty clay were observed to deposit overlying layers containing dark olive-gray very fine to fine sand in the topmost parts of several multiple core samples, with variations in layer thickness observed at various locations. It is considered that seismogenic turbidites, after being transported sand by seismic activity, were re-suspended and redeposited the silty clay above the sand layers due to strong vibrations during the earthquake.
Particularly at TCW-2 site (PC07, total 441 cm in length), multiple sand layers were discovered within bioturbated clay-rich sediment from 0 to 295 cm expected to the Holocene, as observed through X-ray computed tomography (X-CT) scans and visual core observation. The deeper layers observed below the depth of 295 cm, exhibited alternating light and dark bands characteristic of Quaternary deposits in the Japan Sea of glaciation. These sand layers may potentially represent deposits from past large earthquakes, and further sediment analyses as well as the age dating are expected to enable the estimation of the recurrence intervals of past large earthquakes along the Toyama Deep-sea Channel.