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[SGD03-P06] Interplate slip before, during, and after the 2024 Hyuga-nada earthquake
Keywords:Hyuga-nada earthquake, transientt deformation, Satellite geodesy
Abstract
GNSS data was used to estimate pre-, co-, and post-seismic interplate slip for the 2024 Hyuga-nada earthquake in Japan. A slow slip event (SSE) with moment magnitude (Mw) 5.9 was estimated before the earthquake and from late 2023 in the deep extension of the mainshock. Co-seismic slip was estimated adjacent to the focal region of the 1996 Hyuga-nada earthquake. Afterslip occurred near the focal region and in the deep extension of the mainshock, reaching Mw 6.7 on September 16, 2024. The shortened occurrence interval of preslip suggests that SSEs tend to occur prior to earthquakes in Hyuga-nada, which has important implications for earthquake occurrence assessment. The mainshock and afterslip caused increased stress in the surrounding area, especially in the focal region of the 1996 Hyuga-nada earthquake, but on January 13, 2025, a Mw 6.7 earthquake occurred with its hypocenter in the western part of the 2024 Hyuga-nada earthquake.
Introduction
In the Hyuga-nada region, the Philippine Sea Plate is subducting under the Amur Plate in a northwesterly direction at a rate of 4-6 cm per year, and strong interplate earthquakes (Mw 6.8-7.0) occur in Hyuga-nada at 20-30 year intervals. On August 8, 2024, a Mw 7 earthquake occurred in Hyuga-nada. The Kyushu GNSS network detected pre-seismic, co-seismic, and post-seismic crustal deformations. In this study, we estimated the interplate slip before, during, and after the 2024 earthquake based on GNSS data.
Analysis method
To analyze the pre-earthquake stage, we applied NIF to the displacement time series at 130 GNSS points from July 1, 2023 to August 6, 2024, with 0388 points as the reference point. We also applied NIF to data from January 1, 2018 to August 6, 2024 to analyze the occurrence of slow slip events (SSEs) in the past 6 years after the 2016 Kumamoto earthquake. For the post-earthquake deformation, we used data from July 10, 2024 to September 16, 2024. For the coseismic slip, we applied least-squares inversion to the coseismic offset with Laplacian smoothing constraints to estimate the slip distribution. In all analyses, the slip direction was fixed to be opposite to the motion of the Philippine Sea Plate.
Conclusion
Characteristic crustal deformations before, during, and after the earthquake were obtained from the time series data. The time-dependent inversion results showed that a Mw 5.9 SSE had occurred in the deep extension of the hypocenter since the end of 2023. Coseismic slip occurred in the southern vicinity of the focal region of the 1996 Hyuga-nada earthquake. After the earthquake, afterslip occurred in the mainshock focal region and the deep extension of the hypocenter, reaching Mw 6.7 on September 16, 2024.
The pre-earthquake SSEs occurred one year after the latest SSE, while the recurrence interval of previous SSEs were about two years, which shortening is consistent with the characteristics of various simulation results. During the earthquake, post-seismic slip occurred around the focal region of the 1996 Hyuga-nada earthquake, and CFS increased in the focal region of the 1996 Hyuga-nada earthquake. In this context, a Mw 6.7 earthquake occurred on January 13, 2024 with its hypocenter to the west of the 2024 main shock, which may have been triggered by increased stress during and after the 2024 earthquake slip.
GNSS data was used to estimate pre-, co-, and post-seismic interplate slip for the 2024 Hyuga-nada earthquake in Japan. A slow slip event (SSE) with moment magnitude (Mw) 5.9 was estimated before the earthquake and from late 2023 in the deep extension of the mainshock. Co-seismic slip was estimated adjacent to the focal region of the 1996 Hyuga-nada earthquake. Afterslip occurred near the focal region and in the deep extension of the mainshock, reaching Mw 6.7 on September 16, 2024. The shortened occurrence interval of preslip suggests that SSEs tend to occur prior to earthquakes in Hyuga-nada, which has important implications for earthquake occurrence assessment. The mainshock and afterslip caused increased stress in the surrounding area, especially in the focal region of the 1996 Hyuga-nada earthquake, but on January 13, 2025, a Mw 6.7 earthquake occurred with its hypocenter in the western part of the 2024 Hyuga-nada earthquake.
Introduction
In the Hyuga-nada region, the Philippine Sea Plate is subducting under the Amur Plate in a northwesterly direction at a rate of 4-6 cm per year, and strong interplate earthquakes (Mw 6.8-7.0) occur in Hyuga-nada at 20-30 year intervals. On August 8, 2024, a Mw 7 earthquake occurred in Hyuga-nada. The Kyushu GNSS network detected pre-seismic, co-seismic, and post-seismic crustal deformations. In this study, we estimated the interplate slip before, during, and after the 2024 earthquake based on GNSS data.
Analysis method
To analyze the pre-earthquake stage, we applied NIF to the displacement time series at 130 GNSS points from July 1, 2023 to August 6, 2024, with 0388 points as the reference point. We also applied NIF to data from January 1, 2018 to August 6, 2024 to analyze the occurrence of slow slip events (SSEs) in the past 6 years after the 2016 Kumamoto earthquake. For the post-earthquake deformation, we used data from July 10, 2024 to September 16, 2024. For the coseismic slip, we applied least-squares inversion to the coseismic offset with Laplacian smoothing constraints to estimate the slip distribution. In all analyses, the slip direction was fixed to be opposite to the motion of the Philippine Sea Plate.
Conclusion
Characteristic crustal deformations before, during, and after the earthquake were obtained from the time series data. The time-dependent inversion results showed that a Mw 5.9 SSE had occurred in the deep extension of the hypocenter since the end of 2023. Coseismic slip occurred in the southern vicinity of the focal region of the 1996 Hyuga-nada earthquake. After the earthquake, afterslip occurred in the mainshock focal region and the deep extension of the hypocenter, reaching Mw 6.7 on September 16, 2024.
The pre-earthquake SSEs occurred one year after the latest SSE, while the recurrence interval of previous SSEs were about two years, which shortening is consistent with the characteristics of various simulation results. During the earthquake, post-seismic slip occurred around the focal region of the 1996 Hyuga-nada earthquake, and CFS increased in the focal region of the 1996 Hyuga-nada earthquake. In this context, a Mw 6.7 earthquake occurred on January 13, 2024 with its hypocenter to the west of the 2024 main shock, which may have been triggered by increased stress during and after the 2024 earthquake slip.