Developing a Geologically Based VS30 Site-Condition Model for Portugal: Methodology and Assessment of the Performance of Proxies

作者：Vilanova Susana P; Narciso Joao; Carvalho Joao P; Lopes Isabel; Quinta Ferreira Mario; Pinto Carlos C; Moura Rui; Borges Jose; Nemser Eliza S

来源：Bulletin of the Seismological Society of America, 2018, 108(1): 322-337.

DOI：10.1785/0120170213

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 V-S30 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 log V-S30 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 log V-S30 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 log V-S30 values measured and estimated from those proxies are strongly biased for some geological units, emphasizing the need for acquiring regional V-S data.

• 出版日期2018-2