V S Profiles from Noise Cross Correlation at Local and Small Scale

Abstract

Ambient noise measurements have been performed at local and small scales in the Neapolitan and surrounding areas (Campania, southern Italy) by employing two broad-band Kinemetrics Q330 stations, equipped with Episensor ES-T three component accelerometers. In both experiments frequency time analysis (FTAN method) has been performed on the vertical and radial components of noise cross correlations to retrieve the Rayleigh wave dispersion (Green's function). At local scale, over an interstation distance of about 26 km, the group velocity dispersion values have been compared with those obtained from FTAN analysis on recordings of two earthquakes with similar path. At small scale, measurements have been carried out over an interstation distance of about 440 m in the public gardens of Scampia, the northernmost quarter of Naples. The Rayleigh wave group velocity dispersion data obtained from noise cross correlation, have been combined with those from active seismic experiment along the same alignment, but shorter (120 m offset). The non linear inversion of such a dispersion curve has allowed the definition of V S models to depths of 100 m, in agreement with nearby stratigraphy. Moreover, a good agreement has resulted for the resonance frequency among the H/V ratio, the ellipticity of the fundamental mode computed for the chosen V S model, and the average twodimensional (2D) spectral amplification computed along a cross section representative of the Scampia quarter.

Ambient Seismic Noise Tomography of a Loess High Bank at Dunaszekcső (Hungary)

“…In addition, the measurement time depends on station distance, the shorter the distance, the lesser the time required (Sabra et al, 2005b;Gouedard et al, 2008). This method can be equally well used on continental (Yang et al, 2007;Bensen et al, 2009), regional (Szanyi et al, 2013;Ren et al, 2013;Dias et al, 2015), local (Renalier et al, 2010;Stankiewicz et al, 2012) and engineering-geotechnical scale (Picozzi et al, 2009;De Nisco and Nunziata, 2011;Pilz et al, 2012Pilz et al, , 2014.…”

Double-array refraction microtremors

“…The use of 2D arrays is mandatory to identify the source direction: but it is also required in order to identify the velocity and the direction of a wavefield which is not controlled and comes from unknown directions. Varying the frequency range of interest and spatial sampling, 2D array recording of ambient noise was applied as useful tools from shallow soil characterization to deeper regional tomography (see Bonnefoy-Claudet et al, 2006;De Nisco and Nunziata, 2011). In exploration seismology common passive array techniques are: (i) classical beamforming methods such as f-k (Asten and Henstridge, 1984), (ii) spatial autocorrelation SPAC (Aki, 1957), (iii) extended spatial autocorrelation ESAC (Ohori et al, 2002), (iv) high resolution arrays like MUSIC (Schmidt, 1981), and (v) cross-correlation methods (Sabra et al, 2005;Shapiro et al, 2005) and statistical selfalignment property SSAP (Mulargia and Castellaro, 2013).…”