GNGTS 2014 - Atti del 33° Convegno Nazionale

86 GNGTS 2014 S essione 3.1 The survey was composed by 6 patterns; in the first pattern the source was originally located in the first station, with a 6 m as minimum offset, and it represented the beginning of the seismic line at 687 m m.s.l. The subsequent shots were done �������� ������������� ��� ������ �� ��� � shifting progressively the source of 1.5 m along the line, obtaining a gradual decrease of minimum offset (which become equal to zero at the fifth shot) and a transition to a split-spread shot from an off-end shot for the last two. At this point of the work, the source was left in its position and the geophones were instead shifted downwards of 8.25 m along the line, passing to the second pattern, where the entire procedure was repeated until the reach of the last pattern in which the source was progressively Fig. 2 – a) Raw shot gather acquired with NE-SWpolarization; b) raw shot gather with SW-NE polarization, belonging to the same location of the shot displayed in a); c) shot resulting from an optimized sum of shot in a) and shot in b) whose polarity was reversed. In orange, red and green are indicated the direct arrivals and the arrivals from the first refractor and the second refractor respectively; d) shot in c) after the following processing steps: static correction, band pass filter 5-15-100-120 Hz, eigen filter, F-K filter, top mute .