2021 Volume 50 Issue 1 Pages 21-37
Katsuyuki Abe introduced the notion of Tsunami Magnitude (denoted by Mt) for scaling the earthquakes which cause tsunami, measuring the tide-wave-heights, and published a dataset of Mt of tsunamis caused by the earthquakes in the sea around Japan (2006). The dataset includes historical Mt, which extends the original definition and calculated from old documents, monuments and digs. In this paper, we fit the generalized Pareto distribution to the Mt dataset and calculate return periods and other statistics to show the rarity of 2011/03/11 tsunami at the Pacific Ocean coast of Tohoku district.The point is to consider the effect of lost or neglected records in the historical data, as well as the considerable amount of missing data in the measurement of tidal level in the beginning of modern data, and to propose a new model.If the Mt of 03/11 tsunami is included in the dataset, the estimate of parameters change largely, showing the information of big Mt's.
