GNGTS 2017 - 36° Convegno Nazionale

568 GNGTS 2017 S essione 3.1 During the CUMECS-3 cruise have been collected about 260 km of seismic lines while the morphobatymetry data covered an area of about 3400 km 2 along the Malta-Sicily Escarpment. The source used during the seismic survey was a mini GI-GUN (brand Sercel), with charge of 60 in 3 . This tool produces a perturbation with frequency values that can vary from 0 to 128 Hz. It has been designed to remove the reverberations in the input signal, which are due to the bubble effect. During the acquisition, “Harmonic Mode” option was selected to foster a deep penetration of the signal. The source was deployed with a broadside L arrangement at a 1.5 m depth. The Gun controller triggered one shot every 8 seconds, while the shot interval was 15.625 m. Recording gear included a streamer of 300 m with 96 channels. The near offset distance has been maintained to 18,75 m, while the hydrophones were spaced each other of 3.125 m; with this set, fold value was around 9,6. The receivers� ����������� ��� �� � ��������� ������� ������ ’ ����������� ��� �� � ��������� ������� ������ sensitivity was of 9 Volt/bar. Seismic signal was recorded for 7 s with a sampling time of 0,5 ms. The recording was initially filtered to clean the signal through an Ormsby filter, with parameters 12/24-250/500, while Automatic Gain Control (AGC) has amplified the signal. The editing and processing have been done through “Vista Seismic Processing 7.0” software. The ratio signal to noise was enhanced thanks to the following operations: pre-stack spike deconvolution, stacking and time migration. The Reson Seabat 7150 Multibeam echosounder working with a pulse of 12/24 kHz was employed to collect the bathymetric data using the PDS2000 software. The signal amplitude has been corrected according to the grazing angle through the command mbbackangle, the ratio nangle/angle selected was N65.0/64.0. The F5 “beam foot print with slop” gridding algorithms and a tension value of 0.5 have been applied to suppress spurious oscillations and flatten. The final gridplot file has a cell size of 60 m, magnitude of 0.2, azimuth of 0.40 and elevation 35.0. The sub bottom profiler CHIRP II (brand Benthos) was also employed. This instrument has a non-impulsive high frequency source that generates a continuous sweep. It varies in the frequency domain from 2 kHz to 7 kHz. The transducer, modelAT471, is made up of 16 elements that emit the input sweep, whit max. ping rate of 12 ping/sec. During the survey the multiping option was activated. The CHIRP II was handled by SwanPro and ChirpScanII software, which independently processed the signal. They carried out the operations of automatic gain control (AGC) and cross-correlation. The outgoing SEG-Y data have been interpreted with (IHS) Kingdom 8.8 software. The sediment aves, initially identified by Marani et al. (1993) consist in undulations with slopes of less than 2° and variable heights, from ~30 m to ~50 m, which tend to increase northward. Their wave axes have a preferentially direction from NE to SW, and the wave crests are marked by sinuosity and bifurcations. They are characterized by high amplitude and continuity of the seismic reflectors. The stratigraphy analysis allowed us to distinguish four main units. References Manca, B.B., Ursella, L., Scarazzato, P.; 2002: New development of eastern Mediterranean circulation based on hydrological observations and current measurements . Marine Ecology, 23 (SUPPL. 1), pp. 237-257 Marani, M., Argnani, A., Roveri, M., Trincardi, F.; 1993: Sediment drifts and erosional surfaces in the central Mediterranean: seismic evidence of bottom-current activity . Sedimentary Geology, 82 (1-4), pp. 207-220 Miramontes, E., Cattaneo, A., Jouet, G., Th������ ��� ������� ��� ������� ��� �������� ��� ���������� ��� ����� é����� ������� ��� ������� ���������� ��� ����� reau, E., Thomas, Y., Rovere, M., Cauquil, E., Trincardi, F.; 2016: The Pianosa Contourite Depositional System (Northern Tyrrhenian Sea): Drift morphology and Plio-Quaternary stratigraphic evolution . Marine Geology, 378 , 20-42 Sparnocchia, S., Pietro Gasparini, G., Schroeder, K., Borghini, M.; 2011: Oceanographic conditions in the NEMO region during the KM3NeT project (April 2006May 2009). Nuclear Instruments and Methods in Physics Research, Section A, 626-627 (SUPPL.), pp. S87-S90.