The inclusion of site‐specific conditions is essential to adequately represent the seismic hazard and the seismic risk for a region. We acquired, gathered, and organized a near‐surface shear‐wave velocity database for Portugal and applied a three‐step methodological approach for developing a $VS30$ site‐condition map using extrapolation based on surface geology. The methodology includes (1) defining a preliminary set of geologically defined units, (2) calculating the probability distribution of $logVS30$ for each unit, and (3) merging the units according to the results of statistical tests. The final model comprises three geologically defined units characterized by $logVS30$ distributions that are statistically significantly different from each other: F1, igneous, metamorphic, and old sedimentary rocks; F2, Neogene and Pleistocene formations; and F3, Holocene formations. The site conditions for the F3 unit may be further refined using correlations with topographic slope based on the Shuttle Radar Topography Mission at 3 arcsec resolution (SRTM3) dataset. We analyzed the performance site‐condition models based on correlations with exogenous data (topographic slope and surface‐geology analogs). The results show that the residual distributions between $logVS30$ values measured and estimated from those proxies are strongly biased for some geological units, emphasizing the need for acquiring regional $VS$ data.

Vilanova, Susana P. ... et. al.-- 18 pages, electronic supplement http://bssa.geoscienceworld.org/content/104/3/1212/suppl/DC1In probabilistic seismic‐hazard analysis (PSHA), seismic source zone (SSZ) models are widely used to account for the contribution to the hazard from earthquakes not directly correlated with geological structures. Notwithstanding the impact of SSZ models in PSHA, the theoretical framework underlying SSZ models and the criteria used to delineate the SSZs are seldom explicitly stated and suitably documented. In this paper, we propose a methodological framework to develop and document SSZ models, which includes (1) an assessment of the appropriate scale and degree of stationarity, (2) an assessment of seismicity catalog completeness‐related issues, and (3) an evaluation and credibility ranking of physical criteria used to delineate the boundaries of the SSZs. We also emphasize the need for SSZ models to be supported by a comprehensive set of metadata documenting both the unique characteristics of each SSZ and the criteria used to delineate its boundaries. This procedure ensures that the uncertainties in the model can be properly addressed in the PSHA and that the model can be easily updated whenever new data are available. The proposed methodology is illustrated using the SSZ model developed for the Azores–West Iberian region in the context of the Seismic Hazard Harmonization in Europe project (project SHARE) and some of the most relevant SSZs are discussed in detailPeer reviewe