11:30 AM - 11:45 AM
[HDS12-10] A possible source model of the 1512 Eisho tsunami described in an ancient document
Keywords:Historical earthquake, Tsunami, Submarine land slide
We carefully read a bathymetric chart and found a scarp with height of about 400 m and width of about 6000 m at a position about 24 km offshore in the southeastern direction from Shishikui. We also carried out a survey by using a deep-towed sub-bottom profiler (SBP) on ROV NSS during the R/V Hakuho-maru KH-16-5 cruise. The result shows detailed structures possibly caused by a recent landslide. The vertical displacement of the strata was measured to be about 50 m. By considering these results, we constructed a model of submarine mass movement and calculated the initial sea surface displacement by a method of Watts et al. (2005). We investigated several cases by changing movement distances from 800 to 3000 m because it is unknown for one event. For the numerical tsunami simulations, we solved the nonlinear shallow water equations by a finite differential method with a nested grid algorithm which allows the spatial resolution of the study region to be easily increased. The topographic data in Shishikui was made from the present data. But we removed the artificial structures such as wave breakers and altered costal lines by referring to old map images. The numerical summations indicated that the flow depths during the 1512 Eisho tsunami described in SHINCHO-KI could be simulated by the causes using a range from 1400 to 2400 m of movement distance of the submarine mass movement. The maximum tsunami heights of 6 – 9 m were calculated at Shishikui in these cases, while it was 3 m at the maximum along the Kii Peninsula located at the opposite side of the Kii Channel.