GNGTS 2016 - Atti del 35° Convegno Nazionale

GNGTS 2016 S essione 3.2 563 between the lithological calcarenite-sand complex and underlying grey-blue clays. In the eastern area, in contrast, there is a greater lithological variability demonstrated by the marked changes of Vs values. In particular, under the low velocity near surface layer Vs amounts to about 350-450 m/s. This can be attributed to the calcarenite. The underlying layers instead, are characterized by moderately higher Vs values (500-550 m/s), corresponding to Numidian Flysch. In this sector it is well evident the tectonic boundary between the grey-blue clays, present in the western zone, and limestone and flysch, in the eastern one. For more details on seismological analysis, seismic sections spanning a greater depth range (150 m depth under sea level) have been extracted from the 3D seismic model. These seismic sections show a high increase of the shear wave velocity Vs in depth, interpreted as the presence of a seismic bedrock (Vs>800 m/s) due to the underlying Triassic carbonate formations. Conclusions. Shear waves velocity values have been estimated by the HVSR inversion constrained by thickness of the near surface layers detected by lithological logs. The constrained 1D inversion of HVSR curves and bi- and tri-dimensional seismic and lithological modelling by interpolation of geophysical and lithological data allowed to obtain for each seismic layer the variability of shear waves velocity Vs related to the physical-mechanical properties. This process of joint correlation and interpretation has therefore allowed to obtain a high detailed seismostratigraphic model of the studied area. Acknowledgements. We would like to thank the Municipality of Palermo for allowing us to use the stratigraphic and geophysical data of theyr property. References Abate, B., Catalano, R. Renda, P. [1978] Schema geologico dei monti di Palermo (Sicilia). ����� ���� ����� ���� ������� Boll. Soc. Geol. It., 97,807- 819. Bonnefoy-Claudet, S., Cotton, F., Bard. P.Y. [2006] The nature of noise wavefield and its applications for site effects studies. � ���������� ������� ������������� �������� �� ������ ������� ���� �������������������������������� A literature review. Earth-Science Reviews, 79 (3-4), 205-27. doi: 10.1016/j.earscirev.2006.07.004. Catalano, R., Avellone, G., Basilone, L., Contino, A., Agate, M. [2013] Note illustrative della Carta Geologica d’Italia del foglio 595 “Palermo” e carta geologica, scala 1:50.000. ������� ��������� � ������ Regione Siciliana – Ispra. Fäh, D., Kind, F., Giardini, D. [2003] Inversion of local S wave velocity structures from average H/V ratios, and their use for the estimation of site-effects. Journal of Seismology, 7, 449–67. doi: 10.1023/B:JOSE.0000005712.860 58.42. Nakamura, Y. [1989] Method for dynamic characteristics estimation of subsurface using microtremor on the ground surface. Quarterly Report of RTRI (Railway Technical Research Institute) (Japan), 30 (1), 25-33. SESAME [2004] Guidelines for the implementation of the H/V spectral ratio technique on ambient vibrations. Measurements, processing and interpretation. European Commission – Research General Directorate. Project No. EVG1-CT-2000-00026 SESAME. WP12. Fig. 3 – Representation by vertical fences of the shear waves velocity model of the Bandita plain (Palermo).