10:45 AM - 12:15 PM
[MIS16-P02] Attempt to detect tsunami deposits using InSAR analysis
Keywords:InSAR, Tsunami deposit, The 2011 Tohoku-oki tsunami
Tsunami deposits preserved in geological strata may record the long-term tsunami history and can be extremely important data for earthquake and tsunami disaster prevention. However, variability (uncertainty) in geologic surveys is rarely discussed. As a result, information that tsunami deposits are not found is rarely utilized, even though the discovery of tsunami deposits is treated as new knowledge. This is because it is not possible to distinguish whether there are no tsunami deposits in the strata or whether they have not been found due to problems such as the selection of survey sites. To solve this problem, it is necessary to quantitatively understand how tsunami deposits are distributed and to discuss which of them is appropriate to distinguish probabilistically based on the number of survey points. This requires a new data collection method rather than the traditional point data collection.
In this presentation, we present the preliminary results using satellite imagery to detect the areal distribution of tsunami deposits. The target of the analysis is the tsunami deposits formed in the Sendai Plain by the 2011 Tohoku-oki tsunami. Using SAR images before and after the earthquake, we examined whether the tsunami deposits can be detected as vertical displacement of the landform by interferometric SAR analysis. In the analysis, we assumed that the vertical displacement excluding crustal deformation corresponds to the thickness of tsunami deposits, and the crustal deformation was evaluated using displacement data from GPS reference stations. As in Goto et al. [1], we used the thickness of sediment layers observed by Miyagi Prefecture in agricultural lands within the post-disaster inundation area. The InSAR analysis results showed that vertical displacements different from crustal deformation were observed in the inundation area, and that they tended to become smaller toward the inland direction. However, a certain number of interferometric pairs were needed to reduce large variation in the amount of vertical displacement between pairs of SAR images. InSAR analysis showed a layer thickness of 10 cm at the maximum, while the field observations showed a layer thickness of 40 cm at the maximum. In the presentation, we will discuss the validity of the InSAR analysis by comparing the results with the field observations.
In this presentation, we present the preliminary results using satellite imagery to detect the areal distribution of tsunami deposits. The target of the analysis is the tsunami deposits formed in the Sendai Plain by the 2011 Tohoku-oki tsunami. Using SAR images before and after the earthquake, we examined whether the tsunami deposits can be detected as vertical displacement of the landform by interferometric SAR analysis. In the analysis, we assumed that the vertical displacement excluding crustal deformation corresponds to the thickness of tsunami deposits, and the crustal deformation was evaluated using displacement data from GPS reference stations. As in Goto et al. [1], we used the thickness of sediment layers observed by Miyagi Prefecture in agricultural lands within the post-disaster inundation area. The InSAR analysis results showed that vertical displacements different from crustal deformation were observed in the inundation area, and that they tended to become smaller toward the inland direction. However, a certain number of interferometric pairs were needed to reduce large variation in the amount of vertical displacement between pairs of SAR images. InSAR analysis showed a layer thickness of 10 cm at the maximum, while the field observations showed a layer thickness of 40 cm at the maximum. In the presentation, we will discuss the validity of the InSAR analysis by comparing the results with the field observations.