10:45 AM - 12:15 PM
[HDS06-P17] Tsunami simulation for propagating in a river using high-resolution topographic data measured by green laser
Keywords:Tsunami simulation, River run-up
Numerical tsunami calculations require digital topographic data. We generally survey land and sea topography separately and making continuous topographic data at the land-sea boundary is demanding. In recent years, advances in surveys using green lasers have enabled it to obtain continuous, high-resolution topographic data at the boundaries between land and sea. In this study, we conducted a tsunami simulation of river run-up using high-resolution topographic data measured by green laser to determine how much detailed resolution is needed to predict river run-up tsunamis accurately.
This study used the open-source tsunami simulation code (JAGURS, Baba et al., 2015). To verify the accuracy of the JAGURS model, we compared the JAGURS simulation with the analytical solution of Carrier (1991). We computed the tsunami waveforms on a two-dimensional horizontal floor in two cases, Case01 L=85.8 km and Case02 L=343 km, where L is the initial wavelength. The waveforms calculated by linear dispersive wave equations of JAGURS matched the theoretical waveforms.
The spatial grid resolution of the green laser data we used was 50 cm, which is more than ten times higher than the spatial resolution used in tsunami hazard maps. We created five topographic datasets with grid spacing of 0.5 m, 5.0 m, 7.5 m, 10 m, and 15 m to clarify the difference in the calculated tsunami waveforms in a river. The topographic datasets, except for the 0.5 m grid, were generated by resampling from the 0.5 m grid. We calculated a tsunami running up a river using nonlinear long-wave equations. The tsunami source came from the anticipated source model for the great Nankai earthquake proposed by the Cabinet Office, Japan. We investigated the variation of tsunami waveforms with different grid spacings at three virtual observation points upstream, midstream, and downstream of the river. The results showed that the grid with the coarser spacing underestimated the tsunami amplitude. However, the computed waveforms using the 5 m and 0.5 m topographic grids were almost identical. Accordingly, the grid spacing of 5m is sufficient for accurately predicting tsunami propagation on the river.
This study used the open-source tsunami simulation code (JAGURS, Baba et al., 2015). To verify the accuracy of the JAGURS model, we compared the JAGURS simulation with the analytical solution of Carrier (1991). We computed the tsunami waveforms on a two-dimensional horizontal floor in two cases, Case01 L=85.8 km and Case02 L=343 km, where L is the initial wavelength. The waveforms calculated by linear dispersive wave equations of JAGURS matched the theoretical waveforms.
The spatial grid resolution of the green laser data we used was 50 cm, which is more than ten times higher than the spatial resolution used in tsunami hazard maps. We created five topographic datasets with grid spacing of 0.5 m, 5.0 m, 7.5 m, 10 m, and 15 m to clarify the difference in the calculated tsunami waveforms in a river. The topographic datasets, except for the 0.5 m grid, were generated by resampling from the 0.5 m grid. We calculated a tsunami running up a river using nonlinear long-wave equations. The tsunami source came from the anticipated source model for the great Nankai earthquake proposed by the Cabinet Office, Japan. We investigated the variation of tsunami waveforms with different grid spacings at three virtual observation points upstream, midstream, and downstream of the river. The results showed that the grid with the coarser spacing underestimated the tsunami amplitude. However, the computed waveforms using the 5 m and 0.5 m topographic grids were almost identical. Accordingly, the grid spacing of 5m is sufficient for accurately predicting tsunami propagation on the river.