Development of tsunami modelling analysis route
The overall analysis route that has been devised is to use a set of three programs for the three general phases of tsunami modelling: OKADA to generate the initial detailed seafloor displacement boundary condition due to an offshore earthquake, TSUNWAVE to model the wave propagation from the deformed seafloor to near-shore locations, and finally SWASH to model inundation of a coastal land area. The original intention was to use TSUNWAVE for inundation analysis as well, but difficulties were encountered which led to the adoption of the SWASH program.
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Test using Great East Japan earthquake of 2011 tsunami event (1)
The analysis route was then tested using the tsunami event caused by the Great East Japan earthquake of March 11th 2011, also referred to in the literature as the Tohoku earthquake and the 'Off the Pacific coast of Tohoku' earthquake of 2011. A tsunami source devised by Fujii was used in the analysis. Reasonably good results in comparison with measured data were obtained for wave height time histories at GPS buoy locations, and for run-up and inundation height at the Fukushima nuclear plants.
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Test using Great East Japan earthquake of 2011 tsunami event (2)
A further test was carried out to check that the analysis route can reproduce the maximum measured run-up values of about 40 metres in the Iwate region of Japan reported for the tsunami event. Some difficulty in reproducing the high run-up values has been reported in the tsunami modelling literature, and this has led to speculation that a submarine landslide event, triggered by the earthquake, was a substantial contributor to the high run-up values.
It was found that the analysis route can successfully reproduce the maximum measured run-up at the location where it was observed, and predicts even higher values for that particular small stretch of the Iwate coast.
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Submarine slides
A program called SUBSLIDE1 was written to model tsunami waves generated by a submarine slide. The program is compared with results from a wave tank test and gives satisfactory agreement.
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Subaerial slides
A program called SUBSLIDE2 was written to model tsunami waves generated by a subaerial slide consisting of loose material. The program is compared with results from a wave tank test, but calculates a run-up that is substantially higher than the test result.
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A study was carried out using SOLA-3D to investigate whether tsunami waves generated by an asteroid impact can be modelled using the Glasstone & Dolan formula for surface wave heights caused by explosions of underwater nuclear weapons. The formula does appear to work satisfactorily for an asteroid impact.