17:15 〜 18:45
[U15-P75] Sensitivity Analysis for the Tsunami Source Explaining Tsunami Height along the Niigata Coast during the 2024 Noto Peninsula Earthquake
キーワード：2024年能登半島地震、津波、海底地すべり
The Noto Peninsula earthquake, which occurred on January 1, 2024, affected the coast of the Japan Sea. One of the characteristics of this tsunami is the distribution of tsunami heights along the Niigata coast. The tsunami run-up heights were over 5 m around Joetsu (JSCE, 2024), 2.3 m at Sanse on the south coast of Sado Island (Namegaya et al., 2024), and around 2 m or less along the Niigata coast, as represented by a height of around 1.4 m at Kashiwazaki. This local amplification of tsunami height is hardly explained by the fault model estimated from the tsunami waveforms. A massive tsunami has been probably generated locally by submarine landslides.
In this study, to clarify the cause of the abnormal tsunami heights at Joetsu and Sanse, a sensitivity analysis based on tsunami computation was conducted by considering the effect of submarine landslides coupled with the fault model. The numerical tsunami analysis incorporated the submarine landslide model of Yanagisawa et al. (2014) into JAGURS (Baba et al., 2019), and the bathymetry model was based on No et al. (2016). The fault model was adopted from Satake and Fujii (Online). For the submarine landslide conditions, a 10 km square patch was assumed, and the layer thicknesses were varied from 1, 5, to 10 m. A total of 51 scenarios, 17 positions of which were located every 5 km along the western slope of the Toyama Basin off the coast of Suzu, Noto Peninsula, were prepared for sensitivity analysis. The (maximum?) amplitude of the observed tsunami waveforms at Naoetsu and Kashiwazaki were compared with the computation.
The coupled submarine landslide tsunami with a layer thickness of 1 m had only a slight effect on the tsunami heights at Naoetsu and Kashiwazaki regardless of the location of the landslide. For a layer thickness of 5 m, the observed waveform amplitude at Kashiwazaki could be better explained, although the waveform amplitude at Naoetsu was underestimated. For a layer thickness of 10 m, the amplitude was overestimated at Kashiwazaki, but the amplitude could be explained at Naoetsu. In addition, we plan to discuss the size and location of submarine landslides to explain the distribution of tsunami trace heights along the Niigata Coast including those around Naoetsu and Sanse.
In this study, to clarify the cause of the abnormal tsunami heights at Joetsu and Sanse, a sensitivity analysis based on tsunami computation was conducted by considering the effect of submarine landslides coupled with the fault model. The numerical tsunami analysis incorporated the submarine landslide model of Yanagisawa et al. (2014) into JAGURS (Baba et al., 2019), and the bathymetry model was based on No et al. (2016). The fault model was adopted from Satake and Fujii (Online). For the submarine landslide conditions, a 10 km square patch was assumed, and the layer thicknesses were varied from 1, 5, to 10 m. A total of 51 scenarios, 17 positions of which were located every 5 km along the western slope of the Toyama Basin off the coast of Suzu, Noto Peninsula, were prepared for sensitivity analysis. The (maximum?) amplitude of the observed tsunami waveforms at Naoetsu and Kashiwazaki were compared with the computation.
The coupled submarine landslide tsunami with a layer thickness of 1 m had only a slight effect on the tsunami heights at Naoetsu and Kashiwazaki regardless of the location of the landslide. For a layer thickness of 5 m, the observed waveform amplitude at Kashiwazaki could be better explained, although the waveform amplitude at Naoetsu was underestimated. For a layer thickness of 10 m, the amplitude was overestimated at Kashiwazaki, but the amplitude could be explained at Naoetsu. In addition, we plan to discuss the size and location of submarine landslides to explain the distribution of tsunami trace heights along the Niigata Coast including those around Naoetsu and Sanse.