5:15 PM - 6:45 PM
[U15-P32] Strong Motion Generation Areas for the 2024 Noto Peninsula Earthquake Estimated based on the Empirical Green’s Function Method
Keywords:2024 Noto Peninsula earthquake, Strong motion generation area, Empirical Green’s function method
At 16:10 on 1 January 2024 (JST: UTC+9), an Mw 7.5 inland crustal earthquake with reverse faulting occurred in and around Noto Peninsula, central Japan. Within the nation-wide strong motion networks (K-NET and KiK-net) operated by NIED, strong ground motions with large accelerations and velocities were recorded at several stations located in the Noto Peninsula. For understanding the mechanisms of strong motion generation processes during this event, I estimated the source model composed of strong motion generation area (SMGA) to explain the observed strong motion records in broadband frequency range between 0.1 and 10 Hz.
I used the empirical Green’s function method to simulate the ground motion records at 10 K-NET and 8 KiK-net stations located at Ishikawa, Toyama, and Niigata prefectures. For KiK-net stations, the records of downhole sensors were used. From the characteristics of the observed waveforms near the source area, I assumed three squared SMGAs on the fault planes set according to the distribution of the aftershocks occurring within 24 h after the mainshock. The observed ground motion records of Mw 5.4 (10:17 on 2 January 2024) and Mw 5.9 (17:59 on 9 January 2024) events were used as the empirical Green’s functions. The parameters of each SMGA (e.g., the size, relative rupture starting point in SMGA, rise time, and rupture velocity) were estimated by trial-and-error method to be reproduced the observed ground motion records by the simulations.
Overall, the simulated ground motions based on the estimated SMGA model explained well the observed acceleration, velocity, and displacement waveforms at 18 stations. I found the observed ground motions at these stations were generated by the separate contributions of the three SMGAs: The observed large ground motions at ISKH01 (KiK-net Suzu) and ISK001 (K-NET Ohya) were mainly generated from the SMGA1 located including the hypocenter. The SMGA2 set east offshore the Noto Peninsula contributed the reproduction of the observed ground motions at NIG003 (K-NET Sawata) and NIG004 (K-NET Ogi) in Sado Island. The large ground motions at ISK003 (K-NET Wajima) and ISKH04 (KiK-net Togi) were explained by the SMGA3 located beneath Wajima city. As a provisional result, the short-period level of acceleration source spectrum, which is calculated from the sizes and stress drops of the SMGAs, was slightly larger than the empirical scaling relationship (e.g., Tohdo et al., 2022, 2023; Somei et al., 2023) but within the variations for past inland crustal earthquakes. Since there is still room to improve the reproducibility of observed ground motions, the fault geometry and parameters of SMGAs need to be examined objectively in more detail.
Acknowledgements: I used the strong motion data of K-NET and KiK-net operated by NIED.
I used the empirical Green’s function method to simulate the ground motion records at 10 K-NET and 8 KiK-net stations located at Ishikawa, Toyama, and Niigata prefectures. For KiK-net stations, the records of downhole sensors were used. From the characteristics of the observed waveforms near the source area, I assumed three squared SMGAs on the fault planes set according to the distribution of the aftershocks occurring within 24 h after the mainshock. The observed ground motion records of Mw 5.4 (10:17 on 2 January 2024) and Mw 5.9 (17:59 on 9 January 2024) events were used as the empirical Green’s functions. The parameters of each SMGA (e.g., the size, relative rupture starting point in SMGA, rise time, and rupture velocity) were estimated by trial-and-error method to be reproduced the observed ground motion records by the simulations.
Overall, the simulated ground motions based on the estimated SMGA model explained well the observed acceleration, velocity, and displacement waveforms at 18 stations. I found the observed ground motions at these stations were generated by the separate contributions of the three SMGAs: The observed large ground motions at ISKH01 (KiK-net Suzu) and ISK001 (K-NET Ohya) were mainly generated from the SMGA1 located including the hypocenter. The SMGA2 set east offshore the Noto Peninsula contributed the reproduction of the observed ground motions at NIG003 (K-NET Sawata) and NIG004 (K-NET Ogi) in Sado Island. The large ground motions at ISK003 (K-NET Wajima) and ISKH04 (KiK-net Togi) were explained by the SMGA3 located beneath Wajima city. As a provisional result, the short-period level of acceleration source spectrum, which is calculated from the sizes and stress drops of the SMGAs, was slightly larger than the empirical scaling relationship (e.g., Tohdo et al., 2022, 2023; Somei et al., 2023) but within the variations for past inland crustal earthquakes. Since there is still room to improve the reproducibility of observed ground motions, the fault geometry and parameters of SMGAs need to be examined objectively in more detail.
Acknowledgements: I used the strong motion data of K-NET and KiK-net operated by NIED.