2008 年 55 巻 p. 121-125
“Long tail” has been well known for the studies on the internet business. A long tail of statistical distribution shows peculiar properties. Long tail has the moments of lower orders diverge and does not allow us to calcurate the mean nor variance of the focusing variables. Though we belive that there are no such properties in random sea wave fields, almost all of the distributions of wave periods derived by previous theories have long tails. This isa big obstacle for the practical uses of statistical properties of random sea waves. This study shows a path to escape the difficulties.