GNGTS 2015 - Atti del 34° Convegno Nazionale

The ESAC (Extended Spatial Auto-Correlation; Aki, 1957, 1964; Asten and Henstridge, 1984, Ohori et al. , 2002) consists of collecting the ambient seismic noise by means of an array (seismic antenna) employing vertical geophones, laid out in an L, T or X geometry, allowing for different length of the segments in order to fit the available space at the measurement site, especially when in urbanareas. Data are fourier transformed and combined keeping into account the shape of the antenna to obtain the dispersion pattern of the Rayleigh waves. Then, an inversion process allows estimating the local vertical sequence of shear wave velocity (Vs), assuming an 1-D subsurface model. In the present survey, L-shaped arrays, composed of 24 geophones, 8 m spaced, were laid out at each site. We used 3-components 4.5 Hz proper frequency geophones. Seismic noise was recorded separately both for the vertical and horizontal components, obtaining time series of 15 minutes long sampled at 500 Hz. The inversion of the dispersion curves afterwards allowed for the 1-D shear wave velocity estimation using a set of constant thickness layers. Phase velocity data inversion was accomplished using a Tab. 1 - Coordinates (WGS84 – UTM, zone 32N) of the seismic noise measurements. site type of latitude longitude site type of latitude longitude measurement (UTM 32N) (UTM 32N) measurement (UTM 32N) (UTM 32N) 01 array 4946530 714459 14 array 4958360 719532 01 single station 4946550 714380 14 single station 4958390 719530 02 array 4947330 715029 15 array 4959510 720312 02 single station 4947320 715028 15 single station 4959540 720302 03 array 4948470 715036 16 array 4960300 720546 03 single station 4948450 715037 16 single station 4960290 720563 04 array 4949020 715811 17 array 4961180 720964 04 single station 4949020 715802 17 single station 4961190 720981 05 array 4950090 716382 18 array 4962270 721064 05 single station 4950110 716382 18 single station 4962290 721059 06 array 4950990 716572 19 array 4963050 721965 06 single station 4950990 716573 19 single station 4963050 721951 07 array 4951940 716901 20 array 4963680 722199 07 single station 4951930 716899 20 single station 4963670 722225 08 array 4952830 717258 21 array 4964950 722408 08 single station 4952840 717285 21 single station 4964950 722387 09 array 4953800 717964 22 array 4965510 722620 09 single station 4953790 717965 22 single station 4965530 722599 10 array 4954610 718249 23 array 4966490 723283 10 single station 4954610 718264 23 single station 4966480 723278 11 array 4955510 718460 24 array 4967340 723543 11 single station 4955530 718455 24 single station 4967330 723553 12 array 4956410 718774 25 array 4968020 723757 12 single station 4956430 718772 25 single station 4968010 723763 13 array 4957680 719364 26 array 4969380 724651 13 single station 4957670 719364 26 single station 4969390 724638 116 GNGTS 2015 S essione 1.2