A New Methodology for Decreasing Uncertainties in the Seismic Hazard Assessment Results by Using Sensitivity Analysis. An Application to Sites in Eastern Spain

In this study a sensitivity analysis has been carried out by means of the seismic hazard results obtained using the non-zoning methodology (Epstein and Lomnitz, 1966) and the extreme value distribution functions proposed by Gumbel (1958), via a logic tree procedure. The aim of the sensitivity analysis is to identify the input parameters that have the largest impact on assessed hazard and its uncertainty. The research findings from the study of these parameters can serve as a useful guide to facilitate further research studies on seismic hazard evaluations because it allows us to identify parameters that have little or no effect on the seismic hazard results as well as parameters that have great effects on them. In this way, using the obtained results, we have proposed objective criteria in assigning probabilities to the different logic tree branches in a more objective way. It should be noted that, although the sensitivity of the logic tree branches depends on the site, it does not always do so in the same way. Finally, re-evaluation of seismic hazard using the proposed methodology applied to eastern Spain leads to a reduction of uncertainty from 52% to 27% of the expected acceleration with 10% probability of exceedence, at the site with the highest value of seismic hazard (Site 1: Torrevieja).