GNGTS 2017 - 36° Convegno Nazionale

GNGTS 2017 S essione 3.3 693 Colombero C., Baillet L., Comina C., Jongmans D. and Vinciguerra S.; 2017: Characterization of the 3-D fracture setting of an unstable rock mass: From surface and seismic investigations to numerical modeling . JGR: Solid Earth, 122 , 1-21. doi: 10.1002/2017jb014111 Hévin G., Abraham O., Pedersen H.A. and Campillo M.; 1998: Characterisation of surface cracks with Rayleigh waves: a numerical model . NDT&E International, 31 (4), 289-297. Nasseri-Moghaddam A., Cascante G. and Hutchinson J.; 2005: A New Quantitative Procedure to Determine the Location and Embedment Depth of a Void Using Surface Waves . Journal of Environmental and Engineering Geophysics, 10 , 51-64. Zerwer A., Polak M.A. and Santamarina J.C.; 2005: Detection of surface breaking cracks in concrete members using Rayleigh waves . Journal of Environmental and Engineering Geophysics, 10 , 295-306. RPM analysis and advanced joint processing of a SED (Swiss Seismological Service) dataset G. Dal Moro 1 , L. Keller 2 1 Institute of Rock Structure and Mechanics, Prague, Czech Republic 2 roXplore, Amlikon-Bissegg, Switzerland In the framework of a series of site characterizations at some of the seismic monitoring stations operated by the Swiss Seismological Service (Schweizerischer ErdbebenDienst - SED), we recently tested an innovative method for the Holistic acquisition and analysis of the Surface waves (HS) recorded by means of a single 3-component (3C) geophone (Fig. 1). The method originally consisted in the joint analysis of the group-velocity spectra of both the vertical (Z) and radial (R) component, together with the RVSR (Radial-to-Vertical Spectral Ratio) (Dal Moro et al. , 2014, 2015). We here introduce a further object aimed at both further constraining the inversion process (thus obtaining a even more robust shear-wave velocity profile), and at providing to the structural engineers quantitative information regarding the occurrence of Rayleigh-wave prograde motion, recently identified as potential critical factor for the stability of a structure in case of earthquake (Trifunac, 2009). An effectiveway to analyze the actual Rayleigh-wave ParticleMotion (RPM), was introduced in Dal Moro et al. (2017) through the computation, frequency by frequency, of the correlation coefficient between the radial component and the Hilbert transform of the vertical component of Rayleigh waves. The obtained RPM frequency curve (or frequency-offset surface in case of multi-offset data) provides quantitative information about the actual Rayleigh-wave motion (the RPM curve equals to +1 in case of perfectly retrograde motion and to -1 in case of prograde motion) and can be used to further constraining a joint inversion procedure (Dal Moro, 2017; Dal Moro and Puzzilli, 2017). Fig. 1 - Multi-component (single-offset) acquisition of the active data used to implement the HS approach adopted for the present work.