GNGTS 2013 - Atti del 32° Convegno Nazionale

The tectonic activity had resulted in the deposition of thick wedge-like Pliocene-Quaternary depositional succession. The main purpose of this campaign is to identify and characterise possible resonance peaks that may be characteristic of the different lithologies present in the area. A second more wide objective is to identify sites for temporary deployment of a Broad Band 3-component seismometer (30-100 Hz CMG-S3EAM, Guralp, UK) for future evaluation of the possible amplification factors using the FERB/INGV station as reference site (being located on the bedrock, which is present at 130 m depth in correspondence of the Casaglia village, just above the top of the Ferrara Structural High) and comparing the spectra of the vertical and horizontal components of earthquakes being registered by the FERB station and by the temporary MOBFE/UNIFE station. In this paper we shall present the results of the analysis of the Horizontal to vertical Noise Spectral Rations (HVSR) which, once interpreted, would identify resonance peaks that can be related to the presence of sensible seismic impedance contrasts in the subsurface of the urban area of Ferrara, that could result in possible amplification of the seismic signals during their propagation from the focus towards the earth’s surface. HVSR data acquisition and analysis. Twenty sites were surveyed using a 3-component seismometer, with proper frequency of 2 Hz and amplitude response of 78.8 V/(m/s) connected to a 24 bit data logger model VIBRALOG (M.A.E. Molisana Apparecchiature Elettroniche srl, Italy). The seismic noise data were acquired during the period May-June 2013 and consisted in the registration of one hour of seismic noise sampled at 250 Hz. Tab. 1 – Results summary of the encountered H/V spectral peaks. Site ID Time series length (sec) Site name F0 (Hz) H/V amplitude A0 F1 (Hz) H/V amplitude A1 1 60 School: Dosso Dossi 0.8 2.8 0.56 3.0 2 60 Cemetery 0.78 2.8 3 30 Massari park 0.95 2.5 0.40 2.4 4 60 24 May yard 0.71-0.94 2.3/2.2 0.45 2.3 5 60 Angeli Hill 0.95 2.8 0.46 2.2 6 60 School: S. Maria degli Angeli 1.0 3.1 0.46 3.0 7 60 Architecture Department 0.61 3.4 8 60 Pareschi Park 0.88 2.7 0.58 3.0 9 60 Ariosto Library 0.83 2.6 0.56 3.0 10 60 Quacchio Church 0.75-0.91 2.2/2.1 11 60 XX Settembre Street 12 60 S. M. in Vado Church 0.88 2.5 13 60 S. A. in Polesine Church 0.8 2.5 14 60 School: B. Rossetti-Pega 4 0.97 2.0 0.59 2.8 15 60 School: B. Merletti-Galileo 1.0 2.3 0.57 3.1 16 60 School: Guarini-Bellaria 0.79 2.6 0.4 2.1 17 60 Archaeological Museum 0.80 2.4 0.4 2.2 18 60 S. Stefano B. Canale 0.60 2.8 19 60 Residence ASP 20 60 Massari palace F 0 (Hz) Amplitude A 0 F 1 (Hz) Amplitude A 1 Min 0.60 2.0 0.40 2.1 Max 1.00 3.4 0.59 3.0 169 GNGTS 2013 S essione 2.2