Fault geometry through hypocenter clustering

• This page visualizes the 3D fault geometries extraced by our hypocenter clustering method FaultNVC ( Sawaki et al., 2025, JGR ).
• You may download FaultNVC through the Open-File Report of Geological Survey of Japan (Sawaki et al., 2025) .
• Digital data shown here are available in the supplementary materials of each paper.
• Content on this page may be added, revised, or withdrawn without notice.

The 2024 Mw 7.5 Noto Peninsula, central Japan

• We elucidated the fault geometry of the 2024 Mw 7.5 Noto Peninsula earthquake, which occurred on 1 January 2024, using hypocenter clustering.
• Earthquakes listed in the JMA catalog from January 2005 to January 2024 were relocated using tomoDD, and we performed hypocenter clustering for the aftershock sequence from 1–31 January 2024.
• Beneath the peninsula, five fault planes of varying sizes are aligned roughly parallel to the coastline. Along the northern coast, these faults generally dip southward; however, in eastern Wajima, a more counterclockwise-rotated curved fault surface has been identified (ID #142). This area is characterized by the presence of geological boundaries and intrusive diorite bodies, and changes in fault slip behavior have also been suggested (Ando et al., 2025; Honda et al., 2025). In addition, along the western coast, a low-angle east-dipping fault plane (ID #148) is observed.
• The results provide new insights into both the tectonic evolution of the Noto Peninsula and the seismotectonic processes responsible for large inland earthquakes in the region.
• For further details, please refer to the paper below.
  • Sawaki, Y., T. Shiina, K. Sagae, Y. Sato, H. Horikawa, A. Miyakawa, K. Imanishi, and T. Uchide (2025). Fault Geometries of the 2024 Mw 7.5 Noto Peninsula Earthquake from Hypocenter-Based Hierarchical Clustering of Point-Cloud Normal Vectors. Journal of Geophysical Research: Solid Earth, 130(4), e2024JB030233. doi: 10.1029/2024JB030233 (Open Access)
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The Mw 5.0 western Kanagawa, eastern Japan, in August 2025

• We investigated the fault geometry of the aftershock sequence associated with the Mw 5.0 earthquake that occurred in western Kanagawa Prefecture on 9 August 2024.
• Microearthquakes were detected using deep-learning techniques (from July to October 2024), and hypocenters were relocated using a procedure that included waveform cross-correlation.
• We identified a steeply south-dipping distribution extending below the slab interface and extracted the fault plane corresponding to one of the nodal planes of the focal mechanism solution. These results suggest that the earthquake occurred within the Izu-Bonin Arc crust rather than within the island-arc crust or along the plate boundary.
• In the southwestern part of the study area, we also identified planar structures with different strikes, reflecting the complex tectonic architecture of the Izu collision zone.
• For further details, please refer to the paper below.
  • Sawaki, Y., T. Shiina, and T. Uchide (2025). Steep intraplate reverse faulting adjacent to the hypocenter of the 1923 Kanto earthquake: The Mw 5.0 western Kanagawa earthquake in eastern Japan on 9 August 2024. Earth, Planets and Space, 77, 186. doi: 10.1186/s40623-025-02311-9 (Open Access)
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References

• Sawaki, Y., Y. Sato, and T. Uchide (2025). FaultNVC: Earthquake Fault Plane Extractor through Point-Cloud Normal Vector Clustering for Hypocenter Distributions [Software]. Open-File Report of Geological Survey of Japan, AIST, no. 759. https://www.gsj.jp/publications/pub/openfile/openfile0759.html
• Sawaki, Y., T. Shiina, K. Sagae, Y. Sato, H. Horikawa, A. Miyakawa, K. Imanishi, and T. Uchide (2025). Fault Geometries of the 2024 Mw 7.5 Noto Peninsula Earthquake from Hypocenter-Based Hierarchical Clustering of Point-Cloud Normal Vectors. Journal of Geophysical Research: Solid Earth, 130(4), e2024JB030233. doi: 10.1029/2024JB030233 (Open Access)
• Sawaki, Y., T. Shiina, and T. Uchide (2025). Steep intraplate reverse faulting adjacent to the hypocenter of the 1923 Kanto earthquake: The Mw 5.0 western Kanagawa earthquake in eastern Japan on 9 August 2024. Earth, Planets and Space, 77, 186. doi: 10.1186/s40623-025-02311-9 (Open Access)
• Ando, R., Fukushima, Y., Yoshida, K., and Imanishi, K. (2025). Nonplanar 3D fault geometry controls the spatiotemporal distributions of slip and uplift: evidence from the Mw 7.5 2024 Noto Peninsula, Japan, Earthquake. Earth Planets Space, 77, 53. doi: 10.1186/s40623-025-02187-9
• Honda, R., Aoi, S., and Matsubara, M. (2025). Characteristics of the source process of the 2024 M7.6 Noto Peninsula earthquake revealed from back-projection analysis in both low- and high-frequency bands. Earth Planets Space, 77, 149. doi: 10.1186/s40623-025-02281-y