RU2 – INGV RM1: Activity report

Abstract

As part of Task 2 the activities of data collection and compilation of new monographs produced 136 forms on new digital accelerometricstations containing: station coordinates and elevation, photographic documentation and aerial photo of the site. Geological map at 1:25,000 scale, geological sections, respectively at 1:25,000 and 1:2,000 scale are also included. Following the April 6, 2009 L’Aquila earthquake, the activities of new monographs compilation have been redirected on the 57 stations of the AccelerometricNational Network (RAN) which recorded the mainshock. Site classification of ITACA stations according to the EC8-NTC2008 subsoil classes has been revised and the new version (2.0) is going to be released with the next ITACA website upgrade. The ITACA stations are all georeferencedand have been incorporated into a GIS for the assignment of the subsoil category on the basis of the lito-technical map derived from the Geological Map of Italy at 1:100,000 scale. The UR2 planned and realized in Task 4 a seismic network in FucinoBasin. The activity was aimed at detecting amplification effects in the basin and to relate them to the geometrical and geotechnical properties of soft sediments. The network was based on 18 seismic stations deployed between October and January 2009 and was operative until October 2009. In therecording period the seismicity was dominated by L’Aquila earthquake sequence that produced many hundreds record nowadays only partially processed. Many events generated by other seismic region in a 30-40 km distance range were recorded. A preliminary spectral ratios analysis performed and on seismic noise data is presented. The contribution of UR2 to Task 5 consists in an attempt to formulate a new site classification for the Italian territory which could be independent of the knowledge of the site geological conditions and not based on the conventional Vs30 intervals. The innovative approach we introduce for ITACA is based on the estimate of a site predominant period T. For sites where strong ground motions are recorded, the predominant period is identified from the average horizontal-to-vertical spectral ratios of the 5%-damped response spectra of records. The method formulated in Task 5 is applied to the determination of sites with relevant amplification/deamplificationperformed in Task 4.