GNGTS 2022 - Atti del 40° Convegno Nazionale

GNGTS 2022 Sessione 3.2 453 Fig. 1 - Map of the studied area (enclosed by the green dotted line) with the position of the stratigraphic boreholes (yellow dots) and of the seismic noise recordings (green squares) analyzed. Frequencies of the main peaks (numbers in red) are indicated for each noise recording. The iso-depth lines of the Numidian Flysch, defined by Contino et al., 2006, are showed in color-scale. limits of the area are represented by two of the main road axes of Palermo; respectively the northern axis of “Via Lincoln-Corso Tukory-Via Ernesto Basile” and the southern axis of Via Giafar. Avalaible datasets and preliminary analysys. In the above-described area 54 recordings of environmental seismic noise were analyzed. These were carried out in 2016 for the preparation of the “General Town Plan - Palermo 2025 (PRG 2.0)”. The position of microtremor measurements is represented in Fig. 1. The recordings, each of 30 minutes, were analyzed according to the HVSR technique (Nakamura, 1989) and the signals, before being processed, were filtered, excluding from the analysis those time windows probably affected by transient anthropogenic noise. The analysis of the HVSR curves (Fig. 2) allowed to recognize a general trend characterized by the presence of a main peak between about 0.8 Hz and 2.5 Hz and by other secondary peaks at higher frequencies, generally between 15 Hz and 35 Hz. Furthermore, a sharp velocity inversion, defined by the H/V ratio lower than 1, has been recognized for a frequency range between 2.5-3 Hz and 15-20 Hz. Moreover, 50 lithological boreholes located in the studied area (Fig. 1) were taken into consideration. These data are stored in the CityGIS database (Giammarinaro and Maiorana, 2001) managed by the Department of Earth and Marine Sciences of the University of Palermo, that collects stratigraphic and geotechnical data. A preliminary qualitative joint analysis of the boreholes and the microtremor data was realized. The analysis has been implemented by previous bibliographic information on the