Helium isotope anomaly in groundwater prior to the 2024 Noto Peninsula earthquake
Intense earthquake swarms had been observed on the Noto Peninsula in north-central Japan since December 2020. We report data obtained by periodical groundwater sampling and helium isotope measurements in the epicentre area starting July 2022 for investigating the cause of this swarm. The data show mantle-derived helium reaching a maximum of 5 R<sub>a</sub> where R<sub>a</sub> is the atmospheric <sup>3</sup>He/<sup>4</sup>He ratio of 1.39 × 10<sup>-6</sup>. This value indicates that the swarm was caused by fluids rising from the mantle. Time-series analysis show an anomalous drop in helium isotopic ratio prior to the 1 January 2024 Noto earthquake (M7.6), which seriously damaged the region. This decrease in helium isotopic ratio is possibly due to the degassing of radiogenic helium via the deformation of the rocks constituting the groundwater aquifer, which is fundamental and valuable data for predicting inland earthquakes in subduction zones. Periodical observation of helium isotopic ratios in deep groundwater is desirable in regions where a large earthquake is expected.
Authors
- Yasuyuki Kawamoto (ORCID: https://orcid.org/0000-0002-7706-0015)
- Tomo Shibata (ORCID: https://orcid.org/0000-0002-2416-1541)
- Takanori Kagoshima (ORCID: https://orcid.org/0000-0002-8242-3220)
- Yuji Sano (ORCID: https://orcid.org/0000-0002-3305-5644)
- Tomoaki Morishita (ORCID: https://orcid.org/0000-0002-8724-6868)
- Naoto Takahata (ORCID: https://orcid.org/0000-0003-0124-208X)
- Junichi Nakajima (ORCID: https://orcid.org/0000-0002-9584-2627)
- Yoshihiro Hiramatsu (ORCID: https://orcid.org/0000-0001-9874-5059)
- Ying Li (ORCID: https://orcid.org/0000-0001-8522-9020)
Institutions
- Kanazawa University (JP)
- Tokyo Institute of Technology (JP)
- Planetary Science Institute (US)
- Japan Agency for Marine-Earth Science and Technology (JP)
- University of Kochi (JP)
- Fukuoka University (JP)
- ASKA Pharmaceutical (Japan) (JP)
- Sphere Institute (US)
- University of Toyama (JP)
- The University of Tokyo (JP)
- Kōchi University (JP)
- China Earthquake Administration (CN)
Publication Details
- Journal
- Nature Communications
- Published
- 2025-11-26
- DOI
- https://doi.org/10.1038/s41467-025-65717-9
- Primary Topic
- Groundwater and Isotope Geochemistry
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- Japan Society for the Promotion of Science