GNGTS 2014 - Atti del 33° Convegno Nazionale

With the aim of better defining the main geological and structural features of the area, the Galatea vessel performed additional scientific activities, such as magnetic surveys and ROV (Remotely Operated Vehicle) dives. New high resolution shipborne magnetic data were acquired offshore Etna volcano covering either major structural features of Timpe area and Riposto ridge. The magnetic data were collected using a Geometrics G880 caesium-pumped marine magnetometers towed 180 m astern of R/V Galatea. 1-Hz raw readings were geographically referenced in real-time using GPS positions provided by the main navigation system (differential correction by using a Fugro Marinestar VBS). The magnetic survey was planned using a line- path oriented along NE-SW direction in order to intersect the major structural–volcanic features offshore Etna. A total of 1340 linear kilometers of magnetic track lines were acquired using a set of 64 NE-SW parallel lines (with a spacing of 250-300 m) and 8 orthogonal tie lines. Raw magnetic data were processed removing spikes and intervening outliers records, further statistical levelling provided a smooth distribution of magnetic pattern of survey area. The Timpe area shows a high amplitude (>700 nT) magnetic anomaly associated with the main structural elements (NW-SE faults system) suggesting a clear interplay between the tectonic setting and the volcanic manifestations. Interesting magnetic features are observed over the Riposto ridge where small high-frequency positive anomalies (200 nT) are correlated to two small E-W structural highs. 222 GNGTS 2014 S essione 1.3 Fig. 3 – a) Example of shots recording at one OBS; b) preliminary Kirchhoff depth migrated CDP stack of profile T11, shotpoints 400-500.