A research group led by Lecturer Yoshiya Iwasa of the Faculty of Education at the University of Teacher Education Fukuoka, together with Professor Yasuhiro Kumahara of the Graduate School of Humanities and Social Sciences and Professor Emeritus Takashi Nakata at Hiroshima University, Associate Professor Satoru Sugita of the Chubu Institute for Advanced Studies at Chubu University, Assistant Professor Akira Hama of the Graduate School of Horticulture at Chiba University, and Associate Professor Tatsuto Aoki of the College of Human and Social Sciences at Kanazawa University, announced on August 22 that they have revealed that the tsunami height and damage magnitude associated with the 2024 Noto Peninsula earthquake were not proportional. The damage distribution differed from the height distribution and was determined by differences in the peninsula's topographic conditions, settlement location conditions, and the presence or absence of coastal structures. The findings are expected to be utilized for tsunami inundation assumptions and hazard maps. The results were published in Earth, Planets and Space on July 2.
The Noto Peninsula earthquake (M7.6) that occurred in January 2024 caused coastal uplift due to crustal deformation, resulting in the failure of tsunami observation points, and so the heights of the resulting tsunami were unknown.
In this study, the research group investigated detailed tsunami inundation areas and tsunami heights by combining interpretation of high-resolution aerial photographs from the Geospatial Information Authority of Japan (GSI) with field surveys. As a result, they found that the inundation area was 3.7 square kilometers.
Tsunami inundation occurred continuously along the east and west coasts of the Noto Peninsula but was partial on the north coast. On the west coast, notably in Ukai, Suzu City and Shiromaru, Noto Town, tsunamis reached 400-500 meters inland from the coast, causing damage with houses being washed away. These characteristics were consistent with the results of tsunami inundation assumptions made by Ishikawa Prefecture in 2012.
The tsunami height was high on the west coast of the Noto Peninsula, reaching more than 8 meters in elevation at Togi, Shika Town and Kuroshima, Wajima City. On the east coast, it exceeded 5 meters in elevation at Takaya and Jike, Suzu City, and Shiromaru, Noto Town. This is considered to be due to the fault displacement amount and the positional relationship with the source fault. It was also found that the tsunami from the Noto Peninsula earthquake was the largest tsunami to reach the northern part of the Noto Peninsula since the 20th century.
The damage was relatively greater on the east coast than on the west coast, which is inconsistent with the characteristic that tsunamis were higher on the west coast. On the west coast where tsunamis were high, settlements were located on marine terraces elevated above the coastline. It is thought that tsunamis did not reach them due to uplift caused by crustal deformation during the earthquake.
On the other hand, on the east coast, it is estimated that the settlements were located in lowlands directly facing the sea, and the almost complete absence of coastal structures such as breakwaters and seawalls were a factor that increased the damage.
In this research, GIS (Geographic Information System) data of the inundation areas has been published. By using GIS software and maps from the GSI, detailed viewing of tsunami inundation areas is possible.
Iwasa commented: "This research has revealed the overall picture of the tsunami associated with the Noto Peninsula earthquake, and we have found that tsunami heights and damage levels differ according to topographic conditions. The distribution of this tsunami is consistent with hazard map information, and we would like this to be used as an opportunity to reconfirm disaster risks."
Journal Information
Publication: Earth, Planets and Space
Title: Distribution of tsunami inundation area and tsunami height associated with the 2024 Noto Peninsula earthquake, central Japan
DOI: 10.1186/s40623-025-02202-z
This article has been translated by JST with permission from The Science News Ltd. (https://sci-news.co.jp/). Unauthorized reproduction of the article and photographs is prohibited.