17:15 〜 18:45
[SSS05-P12] Simulating Long-Period Ground Motions based on a Dynamic Rupture Simulation for the Nankai Trough Megathrust Earthquake
キーワード：南海トラフ、応力蓄積レート、動力学的断層破壊シミュレーション、長周期地震動
The Nankai Trough, where repeated large historical earthquakes have occurred, is supposed to generate the next megathrust earthquake in the future, and it might bring a tremendous amount of damage to Japanese society. Furthermore, this earthquake is supposed to generate dangerous long-period ground motions that might have a big impact on high-rise buildings. Thus, building an earthquake scenario for this Nankai Trough Earthquake is very critical for hazard mitigation. However, historical records reveal that the ruptured segment of the Nankai Trough is different for each event, suggesting that modeling the whole area of the Nankai Trough without any segmentation is necessary to construct a physically plausible scenario.
We have constructed a physically plausible earthquake scenario for the Nankai Trough megathrust earthquake by considering a realistic plate boundary structure around Nankai Trough (Iwasaki, 2015), as well as the experimental results using fault material (Tsuda and Hirono, 2024, in revision). We have incorporated the initial stress conditions based on the stress rate estimated by Noda et al. (2021). We set the hypocenter location close to a historical earthquake, such as the 1946 Nankai Earthquake, which is the latest earthquake on the Nankai Trough. The stable slip is assumed around the area close to the trench and deeper part that is supposed to host the slow slip. The effective period of the simulation is longer than 3.6 sec. The constructed scenario of this earthquake, whose magnitude is 8.6 and its maximum slip is 8m, shows compatible with-slip distributions from geodetic inversion, such as that by Sagiya et al. (1999). This model generated longer duration of ground motions on the site located inland, even the soft sediment layer is not included. Incorporating such material heterogeneity can provide more realistic scenarios of long-period ground motion.
We have constructed a physically plausible earthquake scenario for the Nankai Trough megathrust earthquake by considering a realistic plate boundary structure around Nankai Trough (Iwasaki, 2015), as well as the experimental results using fault material (Tsuda and Hirono, 2024, in revision). We have incorporated the initial stress conditions based on the stress rate estimated by Noda et al. (2021). We set the hypocenter location close to a historical earthquake, such as the 1946 Nankai Earthquake, which is the latest earthquake on the Nankai Trough. The stable slip is assumed around the area close to the trench and deeper part that is supposed to host the slow slip. The effective period of the simulation is longer than 3.6 sec. The constructed scenario of this earthquake, whose magnitude is 8.6 and its maximum slip is 8m, shows compatible with-slip distributions from geodetic inversion, such as that by Sagiya et al. (1999). This model generated longer duration of ground motions on the site located inland, even the soft sediment layer is not included. Incorporating such material heterogeneity can provide more realistic scenarios of long-period ground motion.