5:15 PM - 7:15 PM
[HDS10-P02] Numerical simulations of tsunamis generated by the 2024 Noto Peninsula earthquake and reflected by the Eurasian continent
Keywords:Tsunami, Noto-Hanto earthquake, Numerical Simulation
On January 1st, 2024, at 16:10 JST, an inland earthquake with a magnitude of 7.6 occurred at a depth of 16 km beneath the Noto Peninsula in Ishikawa Prefecture. A large tsunami was generated and observed along the Japanese coastlines of the Sea of Japan and on the opposite coast along the Eurasian continent. Following the tsunami generated near the Noto Peninsula, the Japan Meteorological Agency (JMA) issued tsunami advisories for coastal regions along the Sea of Japan, from Hokkaido to the western end of the Honshu Island. The tsunami advisories were lifted at 10:00 JST on January 2nd, approximately 18 hours after the main shock. During this period, JMA concerned the potential for tsunami waves to reflect off the opposite coast of the Japanese archipelago, potentially returning to the Sea of Japan with amplified wave heights. This phenomenon, which we hereafter call continental reflection, had been previously observed during the 1983 Japan Sea Central Earthquake (Hatori, 1986) and the 2011 Tohoku Earthquake (Saito et al., 2013). The Japan Meteorological Agency considered the prolonged duration and amplified wave heights due to the influence of continental reflection when deciding to lift the tsunami advisories.
In this study, we investigated the impact of continental reflection, identified by JMA as a key factor in lifting the tsunami advisories, using numerical simulations. First, we calculated the tsunami propagation from the 2024 Noto Peninsula earthquake using the JAGURS tsunami simulation model. The seafloor terrain based on the Global Tsunami Terrain Model was used after resampling of 15 arc-second intervals. The initial water levels were derived from the fault model of the 2024 Noto Peninsula earthquake by Fujii and Satake (2024). The simulation domain covered not only the coastlines of the Japanese archipelago but also the opposite side of the Sea of Japan to capture potential effects of continental reflection. To isolate this effect, we also tested a virtual bathymetric model in which regions with depths of less than 100 meters on the continental side, to the west of a specific reference line, were artificially set to a uniform depth of 100 meters. All other simulation parameters, including grid spacing, were kept the same as in the original model. In this modified bathymetric model, it was confirmed that the tsunami, having crossed the Sea of Japan from the source region, continued to propagate northwestward continued propagating northwestward, with less reflecting at the 100-meter depth zone at the 100-meter depth zone. By comparing the results of the baseline simulation with those from the simulation where the reflection effect on the opposite coast was suppressed, we were able to isolate the influence of reflected waves from the continent.
For further analysis, we calculated envelopes of the wave heights from the simulations. Six domestic observation points (Sado, Nanao, Wajima, Tobishima, Oga, and Fukaura) were used to evaluate the wave heights. The maximum wave height differences, which reflected the effects of continental reflection, were based on the comparison of the simulation results at the following times after the main shock: 24 hours at Sado, 16 hours at Nanao, 22 hours at Wajima, 22 hours at Tobishima, 14 hours at Oga, and 16 hours at Fukaura. The maximum wave height differences occurred after the tsunami advisories had been lifted. It suggests that continental reflection had a significant impact several hours after the initial tsunami arrival. This indicates that the effects of continental reflection became more prominent over time, gradually increasing wave heights as time passed. These results suggest that continental reflection is a significant factor in prolonging the duration of tsunamis and amplifying wave heights.
In this study, we investigated the impact of continental reflection, identified by JMA as a key factor in lifting the tsunami advisories, using numerical simulations. First, we calculated the tsunami propagation from the 2024 Noto Peninsula earthquake using the JAGURS tsunami simulation model. The seafloor terrain based on the Global Tsunami Terrain Model was used after resampling of 15 arc-second intervals. The initial water levels were derived from the fault model of the 2024 Noto Peninsula earthquake by Fujii and Satake (2024). The simulation domain covered not only the coastlines of the Japanese archipelago but also the opposite side of the Sea of Japan to capture potential effects of continental reflection. To isolate this effect, we also tested a virtual bathymetric model in which regions with depths of less than 100 meters on the continental side, to the west of a specific reference line, were artificially set to a uniform depth of 100 meters. All other simulation parameters, including grid spacing, were kept the same as in the original model. In this modified bathymetric model, it was confirmed that the tsunami, having crossed the Sea of Japan from the source region, continued to propagate northwestward continued propagating northwestward, with less reflecting at the 100-meter depth zone at the 100-meter depth zone. By comparing the results of the baseline simulation with those from the simulation where the reflection effect on the opposite coast was suppressed, we were able to isolate the influence of reflected waves from the continent.
For further analysis, we calculated envelopes of the wave heights from the simulations. Six domestic observation points (Sado, Nanao, Wajima, Tobishima, Oga, and Fukaura) were used to evaluate the wave heights. The maximum wave height differences, which reflected the effects of continental reflection, were based on the comparison of the simulation results at the following times after the main shock: 24 hours at Sado, 16 hours at Nanao, 22 hours at Wajima, 22 hours at Tobishima, 14 hours at Oga, and 16 hours at Fukaura. The maximum wave height differences occurred after the tsunami advisories had been lifted. It suggests that continental reflection had a significant impact several hours after the initial tsunami arrival. This indicates that the effects of continental reflection became more prominent over time, gradually increasing wave heights as time passed. These results suggest that continental reflection is a significant factor in prolonging the duration of tsunamis and amplifying wave heights.