Abstract
In order to increase the safety of structures under earthquakes, it is indispensable to add the reliability of estimate of the strong ground motion. Under the assumptions of the Poisson distribution of earthquake occurrence, the Gutenberg-Richter's magnitude law and the attenuation relation, a large number of extreme values of yearly maximum earthquake ground motion are simulated by the Monte Carlo Method. The findings indicate that (1) the plotting position for the extreme values of earthquake ground motions agrees well with that of exponential distributions and (2) the distribution of the largest values is approximated as logarithmic normal distribution. Assuming that the distribution of the largest values is the logarithmic normal distribution, the control curves related to the mean and variance of the largest values can be established by an analytical procedure. As the analytical control curves of ground motions at Fukuoka and Tokyo agree well with the observed distributions for the period of 90 years, it is concluded that the combination of analytical control curves and observed extreme value distributions are convenient for an estimator of the probabilistic design load for the earthquake resisting design.
