GNGTS 2016 - Atti del 35° Convegno Nazionale

404 GNGTS 2016 S essione 2.2 frequency (f1) is comparable in the range of 3-10 Hz to the resonance frequency of the building we note the presence of heavy damaged buildings (Fig. 2 and Fig. 3). So we can hypothesize the coupling between the resonance frequency of subsoil (f 1 ) and that of the damaged building because they have the same range of values (3-10 Hz). In the case of the February 2, 1703 earthquake, we note a similar areal distribution of the heavy damaged buildings of the April 6, 2009 earthquake, hypothesizing a quite similar cause of the building damaging for the February 2, 1703 earthquake. Conclusions. The main conclusions are summarized as follows: the resonance frequency f 1 is caused by the seismic impedance contrast due to the superposition of the Red silt onto L’Aquila breccia (Tab. 1); the damaged/collapsed buildings caused by 1703 and 2009 earthquakes are scattered in areas with subsoil resonance frequencies in the range of 3-10 Hz (Figs. 1 and 2); taking into account the April 6, 2009 earthquake, the 80% of the heavy damaged buildings are placed in sites characterized by f 1 in the range of 3-10 Hz (Fig. 3); the majority of the buildings of L’Aquila historical downtown have a resonance frequency also in the range of 3-10 Hz, so the coupling between the resonance frequency (f 1 ) of subsoil and that of the buildings could be hypothesized because they have the same range of values (3-10 Hz). The ongoing study will investigate this proposed possible coupling phenomena between the resonance frequency of the shallow subsoil model and that of the buildings of L’Aquila historical downtown through GIS zonal statistics analysis and the indirect evaluation of the resonance frequency of the buildings damaged by the February 2, 1703 earthquake. Fig. 3 – L’Aquila historical downtown buildings damage caused by 1703 (A) and 2009 (B) earthquake vs f1 resonance frequency. Data of buildings damage due to the 1703 and 2009 earthquakes are from Clementi and Piroddi (1986) and Tertulliani et al. (2011), respectively. Blue and red colors refer to severe buildings damage or collapse, respectively.