Multiparametric seafloor exploration: the Marsili Basin and Volcanic Seamount case (Tyrrhenian Sea, Italy)

摘要

Exploration of ocean seafloor is of paramount importance for a better understanding of thegeodynamic evolution of our Planet. The pilot experiment of ORION-GEOSTAR 3 EC project was the firstlong-term continuous geophysical and oceanographic experiment of an important seafloor area of SouthernTyrrhenian Sea, the Marsili abyssal plain. The latter hosts the Marsili Seamount which is Europe’s one of thelargest underwater volcano of Plio-Pleistocenic age. In spite of its dimensions, it is rather unknown about thepresent characteristics and activity. For this reason, we deployed a deep-sea observatory network, composedby two bottom observatories, on the seafloor at the base of the seamount at 3320 m b.s.l., in the periodDecember 2003-May 2005. Some of the instruments on board the observatory were: broad-bandseismometers, hydrophones, gravity meter, two magnetometers (scalar and vectorial), 3D single-pointcurrent meter, ADCP, CTD, automatic pH analyser and off-line water sampler for laboratory analyses. Thefirst successful scientific objective was to obtain long-term continuous recordings under a unique timereference. The data analysis shows that they are generally of good quality and really continuous (only a fewgaps). As a first step we performed a classification of seismic waveforms, a first inversion of magneticvariational data, and a first analysis of gravity meter, chemical and oceanographic data. Analysis ofindividual time series has shown interesting results, i.e. depth of the magnetic Moho under the Marsili,attenuation of recorded seismic body waves and clues of hydrothermal circulation. We show examples of thepreliminary data analysis together with first results and comparisons among data coming from differentsensors.