GNGTS 2015 - Atti del 34° Convegno Nazionale

Using the stratified sampling method we identified a sub-populations of 4,000 people within an overall population, with specified characteristics. The criteria adopted were: Geographic Area; Gender; Age; 475-yr return period Peak Ground Acceleration (PGA) of residence area. The first three criteria are generally used in statistical surveys, while the introduction of a new seismic indicator represents a relevant change in this version of the survey. In the first year of our research we chosen to refer to the seismic zones indicated in the national seismic classification (Gruppo di Lavoro MPS 2004, Opcm n. 3274; Stucchi et al. 2011) because we considered that the seismic zone concept could be better understood by general public. Instead, in the present version we refer to PGA values (OPCM 3519/06, 28 April 2006) that are not influenced by regional modification processes. For this reason, when we refer at previous data analysis, the hazard related to the seismic zones is named hazard “by law”, i.e. reported to the regional legislation. The CATI survey was conducted by phone by the operators of the charged company. The numbers and features of the survey are shown in Tab. 1. Tab. 1 - Numbers and features of the CATI survey. Target population Resident population in Italy, 18-80 years, of both sexes belonging to any social condition. Method of sampling Nationally representative, random sample of the Italian population stratified by gender, age, geographical area, PGA. Territorial extension of the survey Throughout the national territory Method of information collection Telephone interviews - C.A.T.I. technique Numerical consistency of the sample Full interviews: 4,012 of respondents Number of non-respondents Waste / non-respondents / non-quota: 35,919 and replacements made Date or period when the survey was carried out 07/01/2015- 09/03/2015 Fig. 1 – Seismic risk perception factors for PGA <0.15 and PGA>0.15. GNGTS 2015 S essione 2.3 295