GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 3.2 617 Carraro F. (Ed.); 1996: Revisione del Villafranchiano nell’area-tipo di Villafranca d’Asti. Il Quaternario (It. Journ. Quatern. Sc.), 9 (1): 5–119. Castellaro S., Mulargia F., Bianconi L.; 2005: Stratigrafia sismica passiva: una nuova tecnica accurate, veloce ed economica. Geologia Tecnica e Ambientale, 3: 76-102. Castellaro S., Mulargia F., 2009: Vs30 estimates using constrained H/V measurements. Bulletin of the Seismological Society of America, Vol. 99, (2A): 761–773. Forno M.G., Gattiglio M., Comina C., Barbero D., Bertini A., Doglione A., Irace A., Gianotti F., Martinetto E., Mottura A., Sala B.; 2015: Stratigraphic and tectonic notes on the Villafranca d’Asti succession in type-area and Castelnuovo Don Bosco sector (Asti reliefs, Piedmont). Alpine and Mediterranean Quaternary, 28(1), 5-27 Grippa A., Bianca M., Tropeano M., Cilumbriello A., Gallipoli M.R., Mucciarelli M., Sabato L.: 2011; Use of the UVSR method to detect buries peleomorphologies (filled incised-valleys) below a coastal plain: the case of the Montaponto plain (Basilicata, southern Italy). Bollettino di Geofisica Teorica ed Applicata, 52, 1-16. Hinzen K.G., Scherbaum F., Weber B.; 2004: On the resolution of H/Vmeasurements to determine sediment thickness, a case study across a normal fault in the Lower Rhine embayment, Germany. J. Earthquake Eng., 8, 909-926. Ibs-von Seht M., Wohlenberg J.; 1999: Microtremor measurements used to map thickness of soft sediments. Bull. Seismol. Soc. America, 89, 250-259. MoHo s.rl. (2011). http://moho.world/ Mucciarelli M., Gallipoli M.R.; 2001: A critical review of 10 years of microtremor HVSR technique. Bollettino di Geofisica Teorica ed Applicata, 42, 255-266. 2D SURFACE WAVE TOMOGRAPHY USING ACTIVE SEISMIC DATA I. Barone 1 , E. Kästle 2 , C. Strobbia 3 , G. Cassiani 1 1 Università degli Studi di Padova, dipartimento di Geoscienze, Padova, Italy 2 Freie Universität Berlin, Institute of Geological Sciences, Berlin, Germany 3 RealTimeSeismic, Pau, France Introduction. Surface Wave Tomography (SWT) is a well-established technique used at regional/global scale to image crustal and upper mantle structures using seismic surface waves produced by strong earthquakes or ambient noise sources. Numerous applications inverting either known earthquake signals (Trampert and Woodhouse 1996, Ekström et al. 1997, Ritzwoller and Levshin 1998) or seismic noise (Boschi et al. 1999, Shapiro et al. 2005, Kästle et al. 2018) have shown the great potential of SWT for retrieving realistic 3D shear wave velocity models. There are only few attempts of applying it to local scale 3D active datasets from seismic exploration, where the near surface characterization is of great interest for improving the continuity of deep reflectors through static corrections (Gouédard et al. 2012, Duret et al. 2016). The aim of this work is testing different tomographical algorithms, originally conceived for seismological applications, on 3D active datasets, and comparing their performances. The method. The work presented here focuses on the tomographical inversion to obtain phase velocity maps at single frequency values. Three different tomographical algorithms were analysed and compared. The first is the Fast Marching Surface Tomography tool (FMST) by Rawlinson and Sambridge (2005), which includes the Fast Marching Method (FMM), a finite difference Eikonal solver, for the solution of the forward problem, and a subspace inversion scheme for the inversion (Kennett, 1988). The second is the Reversible Jump algorithm (Bodin and Sambridge, 2009), which uses FMM for the forward computation and a Markov chain Monte Carlo scheme for the inversion (we will refer to it as RJMCMC, which stands for Reversible Jump Markov Chain Monte Carlo). The third method, named “Eikonal tomography” (Lin et al. 2009), is based on an approximation of the Eikonal equation for high frequency and/or smoothly varying amplitudes. This procedure