Use of 1D and 2D seismic response analyses of soil deposits for seismic Microzonation of urban areas in Tuscany (Italy)

The paper firstly summarizes the main factors affecting seismic response of natural soil deposits with special attention to soil nonlinearity. Then, the available simplified approaches to assess stratigraphic and topographic amplification effects in various codes are discussed.In the second part, the paper shows the results of 1D and 2D Seismic Response Analyses (SRAs), that were performed for the urban centre of Castelnuovo di Garfagnana which is in one of the most seismic areas of Tuscany (Italy). More specifically, the construction of the geotechnical models for seismic response analyses carried out for three cross-sections is illustrated, based on geological and geotechnical information and data available in the Tuscany Region database developed in the framework of the VEL Project. The paper also describes this interactive, georeferenced database. The last part of the paper presents the results of the numerical analyses on selected representative points located along the surface of soil deposit in terms of bar plots of amplification factors. Various available criteria to express 2D amplification effects were considered and summarised. Anyway, the possible aggravation effect was computed by means of an ad - hoc defined parameter. Moreover, possible criteria to extend the SRA results that were obtained for a given geological section over the whole study area were discussed. Use of the average shear wave velocity parameter, V-s,V-30, revealed the most appropriate and cost-effective criterion.