The use of logic trees in probabilistic seismic hazard analyses often involves a large number of branches that reflect the
uncertainty in the selection of different models and in the selection of the parameter values of each model. The sensitivity analysis,
as proposed by Rabinowitz and Steinberg [Rabinowitz, N., Steinberg, D.M., 1991. Seismic hazard sensitivity analysis: a multi-
parameter approach. Bull. Seismol. Soc. Am. 81, 796–817], is an efficient tool that allows the construction of logic trees focusing
attention on the parameters that have greater impact on the hazard.
In this paper the sensitivity analysis is performed in order to identify the parameters that have the largest influence on the
Western Liguria (North Western Italy) seismic hazard. The analysis is conducted for six strategic sites following the multi-
parameter approach developed by Rabinowitz and Steinberg [Rabinowitz, N., Steinberg, D.M., 1991. Seismic hazard sensitivity
analysis: a multi-parameter approach. Bull. Seismol. Soc. Am. 81, 796–817] and accounts for both mean hazard values and hazard
values corresponding to different percentiles (e.g., 16%-ile and 84%-ile). The results are assessed in terms of the expected PGA
with a 10% probability of exceedance in 50 years for rock conditions and account for both the contribution from specific source
zones using the Cornell approach [Cornell, C.A., 1968. Engineering seismic risk analysis. Bull. Seismol. Soc. Am. 58, 1583–1606]
and the spatially smoothed seismicity [Frankel, A., 1995. Mapping seismic hazard in the Central and Eastern United States.
Seismol. Res. Lett. 66, 8–21]. The influence of different procedures for calculating seismic hazard, seismic catalogues (epicentral
parameters), source zone models, frequency–magnitude parameters, maximum earthquake magnitude values and attenuation
relationships is considered. As a result, the sensitivity analysis allows us to identify the parameters with higher influence on the
hazard. Only these parameters should be subjected to careful discussion or further research in order to reduce the uncertainty in the
hazard while those with little or no effect can be excluded from subsequent logic-tree-based seismic hazard analyses