Seismology

We have estimated the fault geometry of the 2024 Noto Peninsula Earthquake in central Japan on 1 January 2024. Our analysis reveals major and minor fault planes aligned along the coastline beneath the peninsula. Notably, we identified a more counter-clockwise rotated plane in eastern Wajima and an east-dipping plane along the west coast. These localized structural complexities suggest intricate fault slip behavior and exhibit a strong correlation with gravity anomalies and geological structures. This research contributes to a deeper understanding of the formation and seismotectonics of the Noto Peninsula.

We also won the AIST President Award 2024 related to Contribution to National Earthquake Disaster Prevention Measures: Response to the 2024 Noto Peninsula Earthquake (in Japanese)!

Check the paper and software 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, e2024JB030233. doi: 10.1029/2024JB030233 (Open Access)
• 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

We imaged the slab and crustal structure of the Kii Peninsula in SW Japan using a receiver-function-like analysis. Positive impedance contrasts in the forearc crust correspond to the top surface or inside Kumano pluton, which may control fluid conditions around slow-earthquake sources.

Check it out below!

• Sawaki, Y., Y. Ito, E. S. M. Garcia, A. Miyakawa, and T. Shibutani (2024). Deep plutonic bodies over low-frequency earthquakes revealed from receiver-side Green’s functions. Tectonophysics, 892, 230536. doi: 10.1016/j.tecto.2024.230536 (Open Access)

We have a new preprint on the seismic structure beneath the Kii Peninsula, southwestern Japan, available on SSRN. While it’s not yet peer-reviewed, feel free to check it out if you’re interested!

Sawaki, Y., Y. Ito, E. S. M. Garcia, A. Miyakawa, and T. Shibutani. Deep Plutonic Bodies Over Low-Frequency Earthquakes Revealed from Receiver-Side Green’s Functions. Available at SSRN: http://dx.doi.org/10.2139/ssrn.4793654

Our new paper is publishded! We analyzed shear wave splitting from receiver functions in Shikoku Island, SW Japan, and along-dip variation of fast axes is clarified. Check it out!

Ruan, Yihuan, Yoshihiro Ito, and Yasunori Sawaki, (2023). Anisotropic Velocity Structure Beneath Shikoku, Japan: Insights From Receiver Function and Shear Wave Splitting Analyses Journal of Geophysical Research: Solid Earth, 128, e2023JB027178. doi: 10.1029/2023JB027178