GNGTS 2017 - 36° Convegno Nazionale

696 GNGTS 2017 S essione 3.3 - in spite of the common belief that Rayleigh waves propagate primarily according to a retrograde motion, prograde motion occurs very frequently and even for very simple subsurface models (such as the one verified in the present case study), away from the classical conditions often invoked to explain it (abrupt V S changes and high Poisson ratios - Tanimoto and Rivera, 2005; Malischewsky et al. , 2008). References Dal Moro G. ; 2017: Improved Holistic Analysis of Rayleigh Waves for Single- and Multi-Offset Data: Joint Inversion of Rayleigh-wave Particle Motion and Vertical- and Radial-Component Velocity Spectra . Pure and Applied Geophysics (in press) Dal Moro G. and Puzzilli L.M.; 2017: Single- and multi-component inversion of Rayleigh waves acquired by a single 3-component geophone: an illustrative case study . Acta Geodynamica Geomaterialia (vol. 14 - in press). Dal Moro G. , Al-Arifi N. and Moustafa S.R.; 2017: Analysis of Rayleigh-Wave Particle Motion from Active Seismics . Bulletin of the Seismological Society of America, 107 , 51-62 Dal Moro G., Keller L. and Poggi V.; 2015: A Comprehensive Seismic Characterization via Multi-Component Analysis of Active and Passive Data. First Break, 33 , 45-53 Dal Moro G., Ponta R. and Mauro R.; 2015: Unconventional Optimized Surface Wave Acquisition and Analysis: Comparative Tests in a Perilagoon Area . J. Appl. Geophysics, 114 , 158-167. Dal Moro G.; 2014: Surface Wave Analysis for Near Surface Applications, Elsevier, Amsterdam, The Netherlands, 252 pp., ISBN 9780128007709. Dziewonski A., Bloch S. and Landisman M.; 1969: A technique for the analysis of transient seismic signals. Bulletin Seismological Society of America, 59 , 427-444. Malischewsky P.G., Scherbaum, F., Lomnitz C., Tuan T.T., Wuttke F. and Shamir G.; 2008: The domain of existence of prograde Rayleigh wave particle motion for simple models. Wave Motion, 45 , 556–564. DOI: https://doi. org/10.1016/j.wavemoti.2007.11.004 Natale M., Nunziata C. and Panza G.F.; 2004: FTAN method for the detailed definition of Vs in urban areas. In: 13 th World Conference on Earthquake Engineering, p. 2694. Vancouver, B.C., Canada. Tanimoto T. and Rivera L.; 2005: Prograde Rayleigh wave motion. Geophys. J. Int., 162 , 399-405. DOI: 10.1111/ j.1365-246X.2005.02481.x Trifunac M.D.; 2009: The role of strong motion rotations in the response of structures near earthquake faults. Soil Dynamics and Earthquake Engineering, 29 , 382-393. Fractured rock mass response to induced vibrations: preliminary results from two test sites D. D’Angiò 1 , L. Curi 2 , M. Fiorucci 1 , R. Iannucci 1 , L. Lenti 3 , S. Martino 1 , A. Paciello 4 1 Department of Earth Sciences and Research Center for Geological Risks (CERI), “Sapienza” University of Rome, Italy 2 Department of Biological, Geological and Environmental Sciences (BiGeA), University of Bologna, Italy 3 French Institute of Science and Technology for Transport, Development and Networks (IFSTTAR), Paris East University, France 4 Italian National Agency for New Technologies, Energy and Sustainable Economic Development, (ENEA) - Casaccia Research Center, Rome, Italy Introduction. Rockslides and rockfalls ��������� ��� �� ��� ���� ��������� ������� ������ represent one of the most hazardous natural events because of the short time available for taking actions in case of exposed infrastructures due to their rapid evolution as well as their hardly detectable precursors. A recent approach devoted to risk prevention consists in performing ambient vibration studies on potentially unstable fractured rock masses, in order to capture permanent changes in their vibrational response that can be related to a ������������� ������� �� �� � ��������� �� ��� ������������ �������� ��� ���� microcracking process �� �� � ��������� �� ��� ���� or to a variation in the pre-existing fracture net (Got et al. , 2010; Levy et al. , 2010; Bottelin et al. , 2013�� �� ���� ���� ������ ��� ��������� �� ). As some rock masses are subjected to the action of external vibrations, for instance those located in proximity of railway lines and highways, their behaviour can change through time also because of anthropic reasons beyond the natural ones linked to variations of environmental parameters.