2023 Fiscal Year Annual Research Report
Largescale numerical investigation on the potential of MTL to produce supershear earthquakes
| Project/Area Number |
22H01573
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| Allocation Type | Single-year Grants |
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| Research Institution | The University of Tokyo |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
加藤 愛太郎 東京大学, 地震研究所, 教授 (20359201)
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| Project Period (FY) |
2022-04-01 – 2026-03-31
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| Keywords | super-shear rupture / effect of geometry / high fidelity models |
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| Outline of Annual Research Achievements |
As planned, we performed large scale simulations of the rupture of the Palu-Koro fault under the initial conditions corresponding to the 2018 event and reproduced the corresponding super-shear rupture. We showed that the initial stress and frictional properties have a significant influence on the nature of the rupture, such as when a rupture jumps to neighboring faults, by simulating several 2D multiple fault systems. We developed two geometric models of the median tectonic line. The first model is based on the data provided by J-SHIS. Although this is the standard model, it is highly simplified. Therefore, we generated an accurate geometric model based on fault trace data from the Geological Survey of Japan (GSJ), and preliminary simulations were performed on coarse mesh models.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
We successfully completed all the tasks planned for FY2023 except SCEC benchmark verification. The reason for this exception is the difficulty of reproducing the artificial initial stresses of the SCEC benchmarks using far-field boundary conditions. To prevent this from hampering our progress, we verified our simulations by reproducing some theoretically expected behavior. We have automated the tedious and time-consuming task of geometric modelling and mesh refinement using fault trace data as input. This allows us to easily correct our models or generate models for other faults. We have submitted two papers to AGU Journal of Geophysical Research and Computational Mechanics by Springer. Successful completion of all planned tasks led us to conclude that the research has progressed well.
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| Strategy for Future Research Activity |
We plan to identify the far-field boundary conditions required to trigger different rupture patterns on a coarse mesh, and simulate fine mesh models of both the simplified fault geometry from J-SHIS data and the detailed geometry from GSJ data. These two simulations will be compared to highlight the importance of using detailed fault models and setting the initial stress consistent with the complex fault geometry and distribution of nonlinear materials. Further, we plan to study the rupture characteristics under heterogeneous distribution of friction parameters. We plan to make another attempt at verification using SCEC benchmark tests to build confidence. Code performance on ARM A64FX based Wisteria supercomputer will be improved since the Oakbridge system has been decommissioned.
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