Abstract
We created a fault model with a Tohoku-type earthquake fault zone having a random slip distribution and performed stochastic tsunami hazard analysis using a logic tree. When the stochastic tsunami hazard analysis results and the Tohoku earthquake observation results were compared, the observation results of a GPS wave gauge off the southern Iwate coast indicated a return period equivalent to approximately 1,709 years (0.50 fractile), and the observation results of a GPS wave gauge off the shore of Fukushima Prefecture indicated a return period of 600 years (0.50 fractile). Analysis of the influence of the number of slip distribution patterns on the results of the stochastic tsunami hazard analysis showed that the number of slip distribution patterns considered greatly influenced the results of the hazard analysis for a relatively large wave height. When the 90 % confidence interval and coefficient of variation of tsunami wave height were defined as an index for projecting the uncertainty of tsunami wave height, the 90 % confidence interval was typically high in locations where the wave height of each fractile point was high. At a location offshore of the Boso Peninsula of Chiba Prefecture where the coefficient of variation reached the maximum, it was confirmed that variations in maximum wave height due to differences in slip distribution of the fault zone contributed to the coefficient of variation being large.
Highlights
In earthquake-induced tsunami hazard analysis, it is extremely important to ascertain the effect of earthquake source parameters on the initial displaced water height of tsunamis
We modeled the hypocenter of the rupture zone of the Tohoku earthquake using the technique of Liu et al (2006) for generating random slip distributions and the technique of Ishii et al (2013) for calculating average slip in the shallow and deep parts
The points of a 10-km mesh encompassing a Tohoku-type earthquake fault zone (500 km 9 200 km) were generated; using the fault parameters in Table 2 and the fault slip artificially generated by the correlated random source parameter (CRSP) model as input values, the initial displaced water height was calculated at those points using the formula of Okada (1985)
Summary
In earthquake-induced tsunami hazard analysis, it is extremely important to ascertain the effect of earthquake source parameters on the initial displaced water height of tsunamis. McCloskey et al (2007, 2008) examined coastal wave height uncertainty for the Sumatra coast using approximately 100 cases of initial displaced water height values calculated from a trench fault with a random slip distribution that was artificially generated in the same manner. They confirmed that nonuniformity of slip distribution greatly influenced coastal wave height. We discuss the regional uncertainty of stochastically assessed tsunami wave height
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