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[STT39-03] Evaluation of long-period ground motions from megathrust earthquakes along the Kuril Trench for wide area
Keywords:Long-period ground motion, Three-dimensional finite element method, Megathrust earthquakes along the Kuril Trench, Kanto area
In the future, there is concern regarding the occurrence of a megathrust earthquake along the Kuril Trench, for which damage estimation results have been disclosed by the Cabinet Office (2021), predicting significant devastation. The occurrence of long-period ground motion may have a considerable impact on structures with long natural periods, such as high-rise buildings and seismic isolation structures.
Long-period ground motions are characterized by their ability to propagate over long distances while maintaining their amplitude. In the Tokachi-oki Earthquake in 2003, sloshing damage to oil tanks occurred in Tomakomai, located 200 km away from the epicenter. In the 2011 off the Pacific coast of Tohoku Earthquake, damage caused by long-period ground motions occurred at the Osaka Prefectural Government Sakishima Building, located 700 km away. Therefore, it is crucial to acknowledge the possibility of long-period ground motions occurrence not only in areas near the epicenter but also hundreds of kilometers away when preparing for a massive earthquake.
Therefore, we conducted a long-period ground motion simulation evaluation for wide area using a three-dimensional finite element method, which encompassed not only the Hokkaido region around the epicenter but also distant areas including the Kanto region, in response to the possibility of a massive earthquake along the Kuril Trench. Nishimoto et al. (2022) have investigated long-period seismic waves by constructing various source models focusing on the Hokkaido region, and we utilized these source models to construct source models for the Nemuro Offshore and Offshore Tokachi areas.
The seismic motions were evaluated using the large-scale 3D-FEM calculation program "E-wave FEM" on the supercomputer "Fugaku". The modeled area is 640 km long, 1,280 km wide including Hokkaido area and Kanto area, and the subsurface structure is based on the Japan Integrated Velocity Structure Model of the Headquarters for Earthquake Research Promotion(HERP). The subsurface structure was extrapolated along the trench axis of the Kuril Trench for the area east of 147 degrees east longitude. The model was divided into tetrahedral quadratic elements with a period of more than 3.3 seconds and a size of five elements per wavelength. The Earth Simulator was used for mesh generation.
We calculated the long-period ground motions using the above analysis method, subsurface model, and seismic-source models. From these findings, we report on the analysis of the occurrence tendencies of long-period seismic waves due to uncertainties in the source parameters, as well as the amplification characteristics of long-period seismic waves in the Kanto Plain.
Acknowledgements : This work was supported by MEXT as “Program for Promoting Researches on the Supercomputer Fugaku” (Large-scale numerical simulation of earthquakes by Fugaku supercomputer, JPMXP1020230213).
This work used the computational resources of the supercomputer Fugaku provided by the RIKEN Center for Computational Science and the Earth Simulator provided by the Japan Agency for Marine-Earth Science and Technology. The results of this work were obtained from the code developed by the Earthquake Research Institute, the University of Tokyo, provided by the Fugaku project and modified and operated by JAMSTEC.We used the Japan Integrated Velocity Structure Model of the HERP and the Deep Subsurface Structure Model of the NIED.
Long-period ground motions are characterized by their ability to propagate over long distances while maintaining their amplitude. In the Tokachi-oki Earthquake in 2003, sloshing damage to oil tanks occurred in Tomakomai, located 200 km away from the epicenter. In the 2011 off the Pacific coast of Tohoku Earthquake, damage caused by long-period ground motions occurred at the Osaka Prefectural Government Sakishima Building, located 700 km away. Therefore, it is crucial to acknowledge the possibility of long-period ground motions occurrence not only in areas near the epicenter but also hundreds of kilometers away when preparing for a massive earthquake.
Therefore, we conducted a long-period ground motion simulation evaluation for wide area using a three-dimensional finite element method, which encompassed not only the Hokkaido region around the epicenter but also distant areas including the Kanto region, in response to the possibility of a massive earthquake along the Kuril Trench. Nishimoto et al. (2022) have investigated long-period seismic waves by constructing various source models focusing on the Hokkaido region, and we utilized these source models to construct source models for the Nemuro Offshore and Offshore Tokachi areas.
The seismic motions were evaluated using the large-scale 3D-FEM calculation program "E-wave FEM" on the supercomputer "Fugaku". The modeled area is 640 km long, 1,280 km wide including Hokkaido area and Kanto area, and the subsurface structure is based on the Japan Integrated Velocity Structure Model of the Headquarters for Earthquake Research Promotion(HERP). The subsurface structure was extrapolated along the trench axis of the Kuril Trench for the area east of 147 degrees east longitude. The model was divided into tetrahedral quadratic elements with a period of more than 3.3 seconds and a size of five elements per wavelength. The Earth Simulator was used for mesh generation.
We calculated the long-period ground motions using the above analysis method, subsurface model, and seismic-source models. From these findings, we report on the analysis of the occurrence tendencies of long-period seismic waves due to uncertainties in the source parameters, as well as the amplification characteristics of long-period seismic waves in the Kanto Plain.
Acknowledgements : This work was supported by MEXT as “Program for Promoting Researches on the Supercomputer Fugaku” (Large-scale numerical simulation of earthquakes by Fugaku supercomputer, JPMXP1020230213).
This work used the computational resources of the supercomputer Fugaku provided by the RIKEN Center for Computational Science and the Earth Simulator provided by the Japan Agency for Marine-Earth Science and Technology. The results of this work were obtained from the code developed by the Earthquake Research Institute, the University of Tokyo, provided by the Fugaku project and modified and operated by JAMSTEC.We used the Japan Integrated Velocity Structure Model of the HERP and the Deep Subsurface Structure Model of the NIED.