Geotechnical characterization for the regional assessment of seismic risk in catalonia

Geotechnical characterization of soils is necessary to evaluate possible amplification of seismic effects in order to assess the seismic risk. The 944 municipalities of Catalonia, with an extension of 31.895 km2 and a population of 6.080.732 inhabitants, present a broad geological variety. This study consists of a geotechnical classification of the municipalities based on the geology of the urban quarters, using four classes of soils: fresh rock; granular compact and coherent soils; altered or fractured rock, granular soils relatively compacts and coherent soils relatively consistents; granular and coherent soft soils. A first approach is carried out from the geological map of Catalonia at 1:250.000 scale available in Arc-Info format. A second approach uses more detailed geological cartography (from 1:200.000 to 1:10.000 scales). A third approach has been undertaken for the main towns of Catalonia (more than 100.000 inhabitants) plus the towns of Girona, Olot and Vielha; for all these towns the available geological cartography (1: 100.000 to 1:22.500) has been digitised. Finally, the geotechnical characterization of Barcelona - where the 25% of the population of Catalonia is concentrated - is performed using the geological map at 1: 22.500 scale from Losan (1978), redrawn to 1: 5.000 scale, digitised and converted to Arc-Info format.