Seismic Response Estimation of the Site of the Italian Accelerometric Station IT.CSA

Date: 4/26/2019

Time: 06:00 PM

Room: Grand Ballroom

The seismic characterization of a site where an accelerometric station is installed is an important task for contributing in the ground motion assessment. This work concerns the site of the accelerometric station IT.CSA, belonging to the Italian Strong Motion Network (Civil Protection Department). This station is located in the municipality of Cannara, Umbria Region (Central Italy) and from its installation in 1986, recorded approximately sixty earthquakes (M >= 4) including events from 1997 Umbria-Marche and 2016 Central Italy seismic sequences. The geological setting of the area consists of a sedimentary deep basin (approximately 1km deep) typical of central Appennines, where Quaternary alluvial deposits overlap a stiff Miocenic geologic bedrock.

The seismic characterization of the IT.CSA site was faced trying to retrieve a characteristic velocity profile by means of 2D passive array data. We installed two different seismic arrays, one equipped with 3-component Lennarts-5s velocimeters and Reftek 130 digitizers, the second by using 72 4.5 Hz vertical geophones connected through cables to three Geode digitizers. The two arrays have been designed with a similar geometry (spiral shape) but with different interstation distance and maximum aperture. This strategy was supposed to be able to reconstruct, with a good resolution, both the shallower and the deeper part of the velocity profile. The collected data have been first processed with the FK analysis to retrieve the dispersion curve and then inverted jointly with the experimental ellipticity (H/V) curve obtained at a station installed close to station IT.CSA. We believe that with this procedure we reconstructed a reliable velocity profile up to the seismic and geologic bedrock.

Presenting Author: Daniela Famiani

Authors