During this meeting it was decided to focus the VOLTAIRE investigation across the Marquês the Pombal - Horseshoe Fault - Guadalquivir Bank structures with additional targets as the NW termination of the accretionary wedge of the Betic-Rif chain and the mud volcanoes that outcrop there. After this meeting, during the first week of July, the maps with the survey planning were submitted to local Portuguese and Moroccan authorities for approval.
Before the start of the campaign, on the first week of October 2002, it has been possible to see the commercial TGS-NOPEC MCS data set. The TGS-NOPEC extended along the whole SW Portuguese continental margin until the depth of 1000 m and helped greatly to select, avoiding useless overlapping, the location of VOLTAIRE MCS lines.
Because the streamer owned by IGM of Bologna showed some dead traces, IGM decided to rent a 48 channel, 600-meters-long streamer from a private company, the Oceansismica - Fugro of Rome. The campaign was carried out on board of the R/V Urania of Italian flag. The R/V Urania departed from the harbour of Livorno on Nov. 21, 2002 with the Italian team embarked and all the equipment for the experiment. In addition to the equipment for MCS acquisition the ship was equipped with facilities for MCS and Chirp processing and interpretation with the aim to either obtain a preliminary interpretation of the data already and the end of the campaign, either to train the young PhD students to geology and geophysics on the field.
During the transit we tested the streamer of Oceansismica. The R/V Urania reached the harbour of Portimão on Nov. 26, 2002 where the non-Italian partners have been embarked. The ship left the harbour on the following day to start the operations. The first day at sea was spent for testing and calibration of the streamer, the GI guns and the acquisition system.
On Friday night, Nov. 28 at about 22.00 GMT, after the acquisition of the first MCS line, we suffered the lost of the whole streamer. The search for the streamer started on the following sunrise. The day after in the early morning we advised the Director of IGM as well the Oceansismica and the Insurance company of the happening. On the same day the personnel of IGM in Bologna started to prepare the IGM streamer for shipment on the following working day (Monday, Dec. 1). The search for the streamer (Fig. 4) was successful and it was recovered on board at around noon time of the 29th of November.
figure
On November 30th the ship stopped nearby Lagos to allow the repairing of the Oceansismica streamer. The damaged stretch section was replaced and the cable was fixed by the end of Saturday 30th. Two birds (Digicourse), out of four, were out of service. Our Spanish colleagues were alerted and ready to ship three replacements. Here we wish to thank them for their effort, kindness and prompt reaction. We show up for the request over the weekend and they were ready to deliver the Digicourse we needed, during the following Sunday.
Unfortunately, on Saturday night, just after the deployment of the streamer for the first test, we found out that the streamer had a second failure at the replaced stretch section. We could not repair the cable anymore for lack of a further stretch section.
The IGM streamer was shipped from Bologna on the following Monday and reached the harbour of Portimão on Thursday Dec. 5. From Monday to Thursday the R/V Urania performed magnetic survey across the Gorringe Bank and the Ampère - Coral Patch Seamounts and two chirp survey to identify coring sites, one across the Portimão Canyon and one along the continental slope South of Cape San Vincente.
In the first place the target was a marked unconformity of probable Miocene age (Mauffret et al., 1989), in the second place the target was a lower sequence underneath the regional Miocene unconformity. The Portimão Canyon was selected for coring and two cores were performed along the canyon. On Thursday afternoon, the IGM streamer was embarked on board and the Oceansismisca streamer was shipped back to the owner in Rome. During the following night the IGM streamer was controlled for functionality.
On Friday 6th at 13.00 the ship left the harbour of Portimão and reached the working area at 15.00 to start the second MCS line. The weather in the following days was variable, sometimes with very rough wind and sea waves. As a consequence the survey was suspended a couple of times with the recovery on board of the streamer and the GI guns array. On Dec. 10 an earthquake of 4.1 of magnitude occurred (frontpage figure) in our study area. The focal mechanism obtained by the INGV indicates a reverse fault with a clear NW-SE compression. On Dec. 12 the Portuguese authorities restricted until Dec. 16 the working area because of military operations. The MCS acquisition ended on Dec. 16, at 01.30 GMT because of rough sea. The equipment was recovered on board by 04:30 GMT and we lead the ship towards Portimão half day in advance because the forecast was foreseeing very rough sea in the following hours.
The acquisition survey ended officially with the arrival of R/V Urania in Portimão on Dec. 16, at 13:00. On Dec. 17, part of the scientific staff disembarked and on Dec. 18 the R/V Urania left the harbour of Portimão at 13:00 with destination Naples. The ship arrived in Naples on the evening of Sunday, Dec. 22. The following day all the equipment was disembarked and shipped to Bologna. On Dec. 24 all the equipment was stored at IGM institute.
![\includegraphics[scale=0.9]{ricerca.eps.conv}](img7.png)