GNGTS 2015 - Atti del 34° Convegno Nazionale

occurrence of buried anticline structures in correspondence to the “condensed” stratigraphy and their recent tectonic evolution. This is further confirmed by a preliminary inversion of some ad-hoc selected HVSR curves, performed using the open source “OpenHVSR” routine, developed by our research group to specifically invert large HVSR datasets; which shall be freely available soon. �� ����� �� ��� �� ��� �������� ������� �� ��� ���� ������ ��� ������ In Figs. 3b and 3c the obtained results of two HVSR curves are shown. The smooth Vs subsurface model obtained from the ESAC was used as starting model for the HVSR inversion. This allowed to start from a model already in the basin attraction of the HVSR inversion global minima. We were so able to optimize the local Vs profiles to both minimize the ESAC and the HVSR objective functions even if the two inversion routines are based on different assumptions. Despite these limitations,, the resultant depth of the major impedance contrast is consistent with those of the other geophysical tests and available information about the subsurface stratigraphy. The comparison with the available stratigraphic data (RER & ENI-AGIP, 1998; Ferrara province – RER, 2007; Martelli et al. , 2014) indicates a good correspondence with the known main stratigraphic unconformities. In particular, the seismic pseudo-bedrock here detected could correspond to the contact between two Middle Pleistocene sedimentary cycles, both belonging to higher rank sedimentary cycle represented by the ����� ������������������ Upper Emiliano-Romagnolo Synthem (AES). Conclusions and future works. The reconstructed pseudo-2D sections document the possibility to highlight the recent tectonic activity of buried structures underlying the eastern sector of the Po Plain by means of low-cost geophysical surveys (not expensive equipment nor large teams). The seismic passive methods allowed collecting a massive dataset in a short period of time, which in turn, allowed retrieving a large number of local 1D shear wave velocity Fig. 3 – a) Smoothed HVSR profile obtained by gridding each average HVSR curve, between 0.5 and 5 Hz. Relative amplitudes are color-coded (see colorbar). The HVSR spectra of each measurement, which were grouped together according to a comparable fundamental resonance frequency, are also shown. b) Result of the HVSR curve inversion of site n. 6 with the “OpenHVSR” routine. On the left graph are shown the observed HVSR spectra (black line) and the best curve obtained after the inversion procedure (red line). On the left diagram are shown the Vs starting model from ESAC survey (blue line) and the final Vs profile relative to the best HVSR curve (red line). c) Result of the HVSR curve inversion of site n. 14. 118 GNGTS 2015 S essione 1.2