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<p>On January 1, 2024, the Noto Peninsula, Japan, was struck by a devastating earthquake with a magnitude (Mj) of 7.6. The Mj7.6 earthquake triggered a series of extensive aftershocks spanning approximately 150&#xa0;km from the southwest coast to the northeast offshore region of the peninsula. While the aftershock distributions likely reflect spatial characteristics of the fault system underlying the Mj7.6 earthquake, the locations of offshore aftershocks remain poorly constrained due to the use of a simplified, land-optimized velocity model. Consequently, the detailed fault system underlying the Mj7.6 earthquake is still unraveled. To address this, we determined the aftershock hypocenters using a well-constructed three-dimensional velocity model for the Noto Peninsula. In our analysis, we employed a method based on the Markov chain Monte Carlo technique to quantify location uncertainties of earthquake hypocenters within the three-dimensional velocity model. The obtained results demonstrated that the aftershocks occurred at depths of 15&#xa0;km or shallower, indicating that the Mj7.6 earthquake ruptured shallow parts of submarine faults and its rupture contributed to tsunami generation. Moreover, the spatial distribution of the aftershock differed markedly from that of the preceding seismicity, including the aftershocks of the 2007 Mj6.9 earthquake at the southwest coast and the intense seismic swarm in the northeastern tip of the peninsula. Overall, these findings suggest that a complex fault network developed across the peninsula would contribute to the rupture processes of the Mj7.6 earthquake and associated seismic activity in this area.</p> Graphical Abstract <p></p>

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Aftershock distribution of the 2024 Noto Peninsula Earthquake, Japan, determined using a 3D velocity structure and uncertainty quantification

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  • 发表日期：

    2025年7月1日

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  • Takahiro Shiina,
  • Haruo Horikawa,
  • Yasunori Sawaki,
  • Kodai Sagae,
  • Kazutoshi Imanishi

摘要

On January 1, 2024, the Noto Peninsula, Japan, was struck by a devastating earthquake with a magnitude (Mj) of 7.6. The Mj7.6 earthquake triggered a series of extensive aftershocks spanning approximately 150 km from the southwest coast to the northeast offshore region of the peninsula. While the aftershock distributions likely reflect spatial characteristics of the fault system underlying the Mj7.6 earthquake, the locations of offshore aftershocks remain poorly constrained due to the use of a simplified, land-optimized velocity model. Consequently, the detailed fault system underlying the Mj7.6 earthquake is still unraveled. To address this, we determined the aftershock hypocenters using a well-constructed three-dimensional velocity model for the Noto Peninsula. In our analysis, we employed a method based on the Markov chain Monte Carlo technique to quantify location uncertainties of earthquake hypocenters within the three-dimensional velocity model. The obtained results demonstrated that the aftershocks occurred at depths of 15 km or shallower, indicating that the Mj7.6 earthquake ruptured shallow parts of submarine faults and its rupture contributed to tsunami generation. Moreover, the spatial distribution of the aftershock differed markedly from that of the preceding seismicity, including the aftershocks of the 2007 Mj6.9 earthquake at the southwest coast and the intense seismic swarm in the northeastern tip of the peninsula. Overall, these findings suggest that a complex fault network developed across the peninsula would contribute to the rupture processes of the Mj7.6 earthquake and associated seismic activity in this area.

Graphical Abstract