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Subsections


INTRODUCTION AND SETTING

Since 2002, after the exhalative crisis of November 2nd ISMAR and INGV have been involved in studying Panarea volcanic complex ANZIDEI2005, COCCHI2008-LOOKING. Cruise PANSTR10 was planned to fill the gap in high resolution gravimetric and magnetometric data, including also Stromboli.

The Aeolian volcanic back-arc (Fig. 1) comprise seven major islands (Alicudi, Filicudi, Salina, Lipari, Vulcano, Panarea and Stromboli), and several seamounts, and are formed by the convergence of the African and Eurasian plates and by the subduction and southeastward rollback of the Ionian lithosphere BARBERI1973, DOGLIONI1991, DOGLIONI1994, CARMINATI1998, ARGNANI2000. It can be subdivided into western, central and eastern sectors DEASTIS2003, characterized by different structural and tectonic evolution, i.e. compression in the western sector, strike-slip faulting and extension in the central and eastern islands.

Panarea is the emergent portion of a submarine stratovolcano more than 2000 m high and 20-km-long across GABBIANELLI1993, GAMBERI1997-AEOLIAN, CALANCHI2002. To the east of Panarea, a group of islets (Basiluzzo, Dattilo, Panarelli, Lisca Bianca, Bottaro, Lisca Nera and Formiche) is present. Panarea is considered inactive, however GAMBERI1997-AEOLIAN have shown possible recent volcanic outcrops near Basiluzzo; present deformation patterns are likely connected to NE-SW trending faults LUCCHI2007.

The gas release of 2002-11-03 E of Panarea, a marine area known since historical times for fumarolic activities ITALIANO1991, generated sustained columns of bubbles from the seafloor to the surface. Several active spots were identified by divers and ROVs' and by repeated multibeam surveys ANZIDEI2005, ESPOSITO2006, ALIANI2010. The most impressive one was just SW of Bottaro (PEG1, Fig. 2 and 3) with gas reaching the surface from 15 m depth, from an elliptic depression produced by the explosive collapse of the seafloor; a plume of sediments was present at the surface for days. Several authors discussed the phenomena in the light of volcanic surveillance and possible regional tectonic connections HEINICKE2009, ACOCELLA2009, WALTER2009.

Figure 2: Panarea I. and Islets.
\includegraphics[width=\linewidth]{IMG/PANAREA_INQ.eps}

Stromboli is a 45-km-long volcanic island in the northeastern-most part of the Aeolian arc. It lies on the thinned crust of the Southern Tyrrhenian continental margin, and deep focus seismicity shows hypocenters in the area of Stromboli at depths between 250 km and 300 km . The continental crust, on which the Aeolian Islands reside, thins out towards the center of the Tyrrhenian Basin and has a crustal thickness of about 18 km underneath the island (Morelli, 1975). A regional zone of crustal weakness controls the magmatic plumbing system and the volcano-tectonic evolution of the Stromboli-Panarea belt LANZAFAME1984, ZANCHI1989, GABBIANELLI1993, BOSMAN2009.

The age of the oldest products has been determined to 100 ka for Stromboli Island and 250 ka for the Strombolicchio volcanic neck GILLOT1993, remnant of an older eroded volcanic edifice OKUMA2009, BOSMAN2009. The evolution of Stromboli presented constructive and destructive phases; the last collapse of the NW flank, which probably occurred a few thousand years ago, generated a subaerial and submarine scar (Sciara del Fuoco'), where a submarine landslide and related tsunami occured 2002-12-29 during a large effusive phenomena CHIOCCI2008SLIDE, CHIOCCI2008RESIL, BOSMAN2009.

Stromboli and Panarea were studied also by refraction and reflection seismic STR06-REP, CASTELLANO2008, BORTOLUZZI2007. An OBS was planned to be deployed and repeat the 2006 experiment MRS06-REP on the Marsili Seamount MARANI2002, COCCHI2009, CARATORI2010. Other 4 OBS were planned to be deployed N of Alicudi I. and on the lineament SE Stromboli NW Marsili looking forward to the forthcoming Refraction and Reflection Seismic Cruise with R/V Sarmiento de Gamboa and R/V Urania within the Spanish-German-Italian MEDOC project to study the Tyrrhenian Sea.

Figure 3: Gas emissions near Bottaro. Modified after ALIANI2010. Top panels show gas flowing SW of Bottaro. Bathymetry and gas locations from ANZIDEI2005.
\includegraphics[width=\linewidth]{IMG/EMISSIONS_P.eps}

Oceanographic setting

The Tyrrhenian Sea exchanges water with the rest of the Mediterranean Sea through the Sardinia Channel,the Sicily Strait and the Corsica Channel, that represent morphologic constraints for the circulation of the intermediate and deep waters MILLOT1987, ASTRALDI1994, SPARNOCCHIA1999, ASTRALDI2001. The surface water (0-200 m) entering the Tyrrhenian Sea through the Sardinia Channel is the Modified Atlantic Water (MAW) from the Algerian Current (AC). The MAW is characterized by low salinity (on average less than 38 PSU), and flows cyclonically along the Italian coast. Through the Sicily Strait and deeper than 200 m down to about 700 m, the basin receives the Levantine Intermediate Water (LIW), which is marked by a subsurface temperature maximum and by a higher salinity (on average 38.8 PSU), and mixes with the surface MAW and deeper water masses. From about 700 m to the bottom the Tyrrhenian Deep Water (TDW) is present, being the result of the modification of the West Mediterranean Deep Water (WMDW) that crosses the Sardinia Channel. The circulation pattern in the Tyrrhenian Sea is normally characterized by two cyclonic gyres in the south and in the northern basins, and by the presence of cyclonic and anticyclonic eddies in the central basin. Interesting features in the TDW ZODIATIS1995 are the thermoaline 'staircase' formations.


next up previous contents
Next: MATERIALS AND METHODS Up: Report on the gravimetric, Previous: PREFACE   Contents
2010-06-10