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[HDS06-P06] Necessities of heterogeneous earthquake slip models for probabilistic tsunami hazard assessments
Keywords:tsunami hazard curve, tsunami analysis
The giant tsunami caused by the 2011 off the Pacific coast of Tohoku earthquake caused extensive damage that exceeded the deterministic tsunami hazard assessment. This has led to the development of probabilistic tsunami hazard assessments, including tsunamis from various earthquakes. The J-THIS Tsunami Hazard Station at the National Research Institute for Earth Science and Disaster Prevention (NIED) has conducted a probabilistic tsunami hazard assessment based on many heterogeneous fault slips. However, for practical use of probabilistic tsunami hazard assessment, it is necessary to profoundly investigate the assessment results (e.g., hazard curves). Therefore, this study aims to quantitatively demonstrate the necessity of considering heterogeneous slips in earthquake scenarios for probabilistic tsunami hazard assessments.
We compared the tsunami hazard curves constructed from 3480 heterogeneous slips and 83 homogeneous slips. We, here, considered the variation in tsunami calculations with the parameter proposed by the previous study (σ = 0.35). In the Kyushu region, the deviation between the hazard curves from heterogeneous slips and homogeneous slips increased as the maximum tsunami height increased. The exceedance probability of heterogeneous slip was high, and this is because the heterogeneous slips have large and super-large slip areas. The tsunami height increases when a large slip area is located near the evaluation point. The tsunami hazard curve generated from the homogeneous slip scenario with the value of σ changed to 0.65 was almost the same as that for the heterogeneous slip with σ = 0.35. In the Setouchi area, there was no difference between the tsunami hazard curves from the heterogeneous and homogeneous slips (both with σ = 0.35). This may be because the Setouchi area is far from the source and is not affected by heterogeneity on fault slip. The tsunami hazard curves generated from the homogeneous slips with σ = 0.65 greatly exceed those of the heterogeneous slips with σ = 0.35. Therefore, it does not seem to be sufficient to change the value of σ to reproduce the tsunami hazard curve of the heterogeneous slips using only the homogeneous slips model, which has a low tsunami calculation cost.
We compared the tsunami hazard curves constructed from 3480 heterogeneous slips and 83 homogeneous slips. We, here, considered the variation in tsunami calculations with the parameter proposed by the previous study (σ = 0.35). In the Kyushu region, the deviation between the hazard curves from heterogeneous slips and homogeneous slips increased as the maximum tsunami height increased. The exceedance probability of heterogeneous slip was high, and this is because the heterogeneous slips have large and super-large slip areas. The tsunami height increases when a large slip area is located near the evaluation point. The tsunami hazard curve generated from the homogeneous slip scenario with the value of σ changed to 0.65 was almost the same as that for the heterogeneous slip with σ = 0.35. In the Setouchi area, there was no difference between the tsunami hazard curves from the heterogeneous and homogeneous slips (both with σ = 0.35). This may be because the Setouchi area is far from the source and is not affected by heterogeneity on fault slip. The tsunami hazard curves generated from the homogeneous slips with σ = 0.65 greatly exceed those of the heterogeneous slips with σ = 0.35. Therefore, it does not seem to be sufficient to change the value of σ to reproduce the tsunami hazard curve of the heterogeneous slips using only the homogeneous slips model, which has a low tsunami calculation cost.