Communicating with uncertainty: A critical issue with probabilistic seismic hazard analysis

Abstract

Probabilistic seismic hazard analysis (PSHA) is a widely used method for seismic hazard assessment. PSHA predicts a relationship, called the seismic hazard curve, between the maximum ground motion or response spectra and the annual frequency of exceedance (return period). Generally, the smaller the annual frequency of exceedance, meaning the longer the return period, the larger the ground motion— seismic hazard—PSHA will predict, and vice versa. PSHA is the most widely used method for assessing seismic hazards for input into various aspects of public and financial policy.

Comment by R. M. W Musson on “Comparison between probabilistic seismic hazard analysis and flood frequency analysis”

“…Musson 's [2004] comment on an earlier paper by Wang et al [2003] was addressed in a response by Wang et al [2004]. However, it seems that Musson is still sure he is right and Wang et al are all wrong when he says, "I pointed out [Musson, 2004] the fallacies in a paper by Wang et al [2003] .These errors are now repeated by Wang and Ormsbee [2005], who refer back to Wang et al [2003] but not to Musson [2004]."…”

“…I pointed out [Musson, 2004] the fallacies in a paper by Wang et al [2003] .These errors are now repeated by Wang and Ormsbee [2005], who refer back to Wang et al [2003] but not to Musson [2004].…”

“…However, it seems that Musson is still sure he is right and Wang et al are all wrong when he says, "I pointed out [Musson, 2004] the fallacies in a paper by Wang et al [2003] .These errors are now repeated by Wang and Ormsbee [2005], who refer back to Wang et al [2003] but not to Musson [2004]." Now Musson is trying to impose his self-righteousness on the whole scientific community by asking Eos not to publish any paper that contains a point of view different from his.…”

Reply [to “Comment on ‘Communicating with uncertainty: A critical issue with probabilistic seismic hazard analysis’” by R. M. W. Musson]

“…PSHA cannot define the worst-case ground motion scenario, because the results from PSHA are hazard curves and there is no reference point on the curves that is a minimum or maximum [Wang et al, 2003] .This is obvious. It is not, as Musson says in his comment/'because hazard curves extend to infinitely strong ground motion at infinitely long return periods.…”

“…Lastly, Wang et al [2003] point out that PSHA studies present the user with an infinite num ber of choices. From a hazard curve spanning probabilities from 10" 1 to 10 s per annum, the user can pick a value corresponding to any probability level chosen.The user is given no guidance as to which level to pick.…”