Reply to the comment on J.U. Klugel's: Problems in the application of the SSHAC probability method for assessing earthquake hazards at Swiss nuclear power plants, in Engineering Geology, Vol. 78, pp. 285-307, by Wang, by J.U, Klugel

摘要

In his discussion paper Dr. Wang (Wang, 2005) presents an illustrative analysis of the statistical meaning of the annual probability of exceedance (gamma) as it is calculated by a PSHA-model in common use in the U.S.A. Based on the assumption that the seismic activity of the area of interest is caused by an ensemble of seismic sources (e.g. faults), which can be characterized by their characteristic magnitudes, Dr. Wang demonstrates that, due to the aggregated nature of the PSHA model the statistical meaning of the obtained ground motion results gets lost. In his opinion, this explains the many inconsistencies, which were established in the paper discussed (Klugel, 2005). Especially a comparison with historical seis-micity is not possible, because the results of a PSHA are not physical, while historic seismicity is. Therefore, a ground motion which is characterized by a calculated return period of 2500 years will not occur once within this return period, but will be exceeded with a set of certain probabilities, if all the considered underlying characteristic earthquakes occur. The final conclusion is, that PSHA does not provide a unique choice for users and decision makers to define a design basis earthquake but infinite choices.