Seismic risk analysis of discrete system of sites

Two efficient schemes have been developed for the analysis of discrete systems of sites. Both schemes have the same objective of finding the probability of simultaneous failure of any number of sites belonging to a given system of sites subject to threats from a given set of earthquake sources with known seismic history. In the first scheme, systems with deterministic site resistances can effectively be analysed using a non-linear transformation of variables. In the second scheme, systems with random site resistances can be analysed. To overcome the computational difficulties involved in the analysis, a new set of simple recursive formulas has been developed and used effectively. Based on these two schemes, two efficient computer programs were prepared and used to perform a parametric study on a system of nine actual or contemplated nuclear power plants in New England. The results have shown that the problem is very sensitive to the coefficient of variation of the resistances and not so sensitive to the mean resistances.