Exploration of ocean seafloor is of paramount importance for a better understanding of the
geodynamic evolution of our Planet. The pilot experiment of ORION-GEOSTAR 3 EC project was the first
long-term continuous geophysical and oceanographic experiment of an important seafloor area of Southern
Tyrrhenian Sea, the Marsili abyssal plain. The latter hosts the Marsili Seamount which is Europe’s one of the
largest underwater volcano of Plio-Pleistocenic age. In spite of its dimensions, it is rather unknown about the
present characteristics and activity. For this reason, we deployed a deep-sea observatory network, composed
by two bottom observatories, on the seafloor at the base of the seamount at 3320 m b.s.l., in the period
December 2003-May 2005. Some of the instruments on board the observatory were: broad-band
seismometers, hydrophones, gravity meter, two magnetometers (scalar and vectorial), 3D single-point
current meter, ADCP, CTD, automatic pH analyser and off-line water sampler for laboratory analyses. The
first successful scientific objective was to obtain long-term continuous recordings under a unique time
reference. The data analysis shows that they are generally of good quality and really continuous (only a few
gaps). As a first step we performed a classification of seismic waveforms, a first inversion of magnetic
variational data, and a first analysis of gravity meter, chemical and oceanographic data. Analysis of
individual 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 the
preliminary data analysis together with first results and comparisons among data coming from different
sensors

Beranzoli, L.

Calcara, M.

Ciafardini, A.

De Caro, M.

De Santis, A.

Favali, P.

Frugoni, F.

Iafolla, V.

Lo Bue, N.

Marinaro, G.

Monna, S.

Montuori, C.

Qamili, E.

Sgroi, T.

Vitale, S.

Earth-prints Repository

Proceedings of the 3rd IASME/WSEAS International Conference on Geology and Seismology (GES’09), pp.153-157                             
ISSN: 1790-2769                                                                                                                           ISBN:978-960-474-058-1 
Multiparametric seafloor exploration: the Marsili Basin and Volcanic 
Seamount case (Tyrrhenian Sea, Italy) 
  
 
L. BERANZOLI(1), A. DE SANTIS (1,2), M. CALCARA(1), A. CIAFARDINI(3), M. DE CARO(1), P. 
FAVALI(1,4), F. FRUGONI(1), V. IAFOLLA(5), N. LO BUE(1), G. MARINARO(1), S. MONNA(1), C. 
MONTUORI(1), E. QAMILI (1), T. SGROI(1), S. VITALE(6) 
(1) Istituto Nazionale di Geofisica e Vulcanologia, Roma, Italy (2) Chieti University, Chieti, Italy               
(3) GEOTEC spa, Campobasso, Italy (4) “Sapienza” University, Roma, Italy (5) CNR, IFSI-INAF Roma, 
Italy (6) ENI E&P, San Donato Milanese, Italy 
beranzoli@ingv.it; http://www.ingv.it 
 
 
Abstract: - Exploration of ocean seafloor is of paramount importance for a better understanding of the 
geodynamic evolution of our Planet. The pilot experiment of ORION-GEOSTAR 3 EC project was the first 
long-term continuous geophysical and oceanographic experiment of an important seafloor area of Southern 
Tyrrhenian Sea, the Marsili abyssal plain. The latter hosts the Marsili Seamount which is Europe’s one of the 
largest underwater volcano of Plio-Pleistocenic age. In spite of its dimensions, it is rather unknown about the 
present characteristics and activity. For this reason, we deployed a deep-sea observatory network, composed 
by two bottom observatories,, on the seafloor at the base of the seamount at 3320 m b.s.l., in the period 
December 2003-May 2005. Some of the instruments on board the observatory were: broad-band 
seismometers, hydrophones, gravity meter, two magnetometers (scalar and vectorial), 3D single-point 
current meter, ADCP, CTD, automatic pH analyser and off-line water sampler for laboratory analyses. The 
first successful scientific objective was to obtain long-term continuous recordings under a unique time 
reference. The data analysis shows that they are generally of good quality and really continuous (only a few 
gaps). As a first step we performed a classification of seismic waveforms, a first inversion of magnetic 
variational data, and a first analysis of gravity meter, chemical and oceanographic data. Analysis of 
individual 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 the 
preliminary data analysis together with first results and comparisons among data coming from different 
sensors.  
 
Key-Words: Marsili Basin and Volcanic Seamount, Exploration with seafloor observatories, ORION-
GEOSTAR 3 EC project 
 
1 Introduction 
Our Planet is a complex system where different 
macro-components, such as hydrosphere, 
geosphere, biosphere and atmosphere, interact on 
different spatial and time scales. In particular, 
oceans, covering more than 7/10 of the Earth 
surface, still remain largely unexplored and a 
variety of processes and interactions of different 
nature taking place inside them are poorly known. 
In the last decades of the previous century the 
extension of experimental observations on the 
seafloor has represented the actual challenge to 
start an innovative long-term and multidisciplinary 
investigation, improving the traditional periodic 
and episodic exploration campaigns. Study of the 
deep seafloor helps us: a) to understand submarine 
geodynamics, composing the complex dynamics of 
all structural elements of plate tectonics; b) to 
discover and reconstruct the climate change history 
and its effects on the ecosystems. The scientific 
discovery and achievement are strongly dependent 
on the availability, accessibility and novelty of the 
ocean technology and infrastructures. This requires 
continuous innovation in marine engineering and 
knowledge transfer from a wide range of technical 
disciplines such as robotics, communications, 
energy, to scientists, and then to policymakers [1]. 
Marine technology has strongly evolved over the 
past decades and has been offering new tools to 
achieve significant advances. As an example, deep-
sea vehicles (ROVs, AUVs, crawlers, etc.) are now 
key tools for the exploration of the deep ocean 
realms as well as drill ships, which can provide 
long records into the past. Moreover, since 
development and research in industry run in 
parallel, the scientific community has benefited 
Proceedings of the 3rd IASME/WSEAS International Conference on Geology and Seismology (GES’09), pp.153-157                             
ISSN: 1790-2769                                                                                                                           ISBN:978-960-474-058-1 
from a mature industrial supplier base and has been 
able to progress towards greater depths and higher 
reliability regarding new sensor systems for 
physical, chemical and oceanographic in situ 
measurements. In this regard, the recent 
development of long-term, multiparameter seafloor 
observatories has replied to a major challenge - the 
acquisition of long-term time series in deep sea 
waters – which in essence adds the fourth 
dimension to a 3D understanding of the 
phenomena. The fourth dimension, i.e. temporal 
variability, is critical for many processes on Earth, 
for instance the periodicity of fluid flow, rates of 
active tectonics, recurrence intervals of geo-
hazards (e.g., earthquakes, tsunamis), and 
ecosystem life cycles. 
Specifically, from the European Commission (EC) 
FP5 up to the present running FP7, the European 
scientific community has been involved in several 
important initiatives addressed to long-term 
observation and state-of-the-art deep-sea 
technology. Development of European seafloor 
observatories with multidisciplinary capabilities 
has been pioneered under the EC-funded 
GEOSTAR projects [2, 3, 4].  
This brief paper gives some information about the 
seafloor mission performed under ORION-
GEOSTAR 3 EC project in the Marsili Basin 
(Southern Tyrrhenian Sea), close to the Marsili 
Volcanic Seamount. In the following sections we 
will show examples of the preliminary data 
analysis together with first results and comparisons 
among the data coming from different sensors. 
 
 
 
 
Fig. 1. Heat flow (mW/m2) of the Southern 
Tyrrhenian Sea [6]. 
 
 
2 Marsili Basin and Volcanic 
Seamount pilot experiment  
The Marsili Basin has developed in the last 2 Ma 
[5]. It is the most recent ocean crust floored basin 
presenting all the characteristics of oceanic back-
arc spreading basin with high values of heat flow 
(Fig. 1; after [6]) and low values of Moho isobaths 
(Fig. 2; after [7]).  
However it lacks the typical morphology of a 
spreading centre where new crust is produced. 
Instead, the central youngest part of the basin is 
occupied by the Marsili Volcanic Seamount, 
discovered in the 1920s, with a volume of 1400 
km3, an elevation of about 3000 m from the 
basement level of the basin and a strongly NNE-
SSW elongated structure [8]. This volcanic 
structure is one of the largest European underwater 
volcanoes of Plio-Pleistocenic age and is a key to 
understanding the mechanisms driving the 
lithosphere formation and dynamics in the 
Tyrrhenian Sea. The Marsili Basin has been the 
objective of ship-based pioneer exploration from 
1970s [9], however its geophysical characteristics 
and activity have remained mostly unknown so far 
(small square in Fig. 3 shows the area of interest). 
Marsili volcano, showing remarkable similarities 
to the mid-oceanic ridges, has been recently 
interpreted as a super-inflated spreading ridge [10, 
11].  
Fig. 2. Moho isobaths (km) of the Italy and 
surrounding seas [7]. 
 
The first long-term continuous geophysical and 
oceanographic experiment dedicated to the study 
Proceedings of the 3rd IASME/WSEAS International Conference on Geology and Seismology (GES’09), pp.153-157                             
ISSN: 1790-2769                                                                                                                           ISBN:978-960-474-058-1 
of the long-term activity of the Marsili seamount 
was carried out in the frame of the ORION-
GEOSTAR 3 EC project (2002-2005), where a 
deep-sea observatory network, including two 
multi-sensors observatories, was deployed on the 
seafloor at the base of the seamount at 3320 m 
b.s.l., in two separate legs between December 2003 
and May 2005 (seafloor location of the 
experiment: 39°29’12” N, 14°19’52” E;). Besides 
oceanographic sensors, geophysical instruments 
were installed on board the observatories: 3D 
broad-band seismometers, hydrophones, gravity-
meter, two magnetometers (scalar and vectorial) 
(Fig. 4).  
 
Fig. 3. Bathymetry of the Southern Tyrrhenian 
Basin; the Marsili Seamount is marked by the 
small square [8]. 
 
Given an overall duration of the seafloor 
monitoring of 477 days, this experiment has 
produced the first long multi-sensor time-series, 
for a total data amount of 28.5 Gbytes. 
 
3 Seafloor data  
The first successfully scientific objective was the 
acquisition of long multiparameter time-series 
under a unique time reference thanks to a 
centralised data acquisition and clock. The data 
quality check, which is always performed before 
the data analysis and elaboration, 
shows that data are of good quality, and in general 
continuous with only a few gaps.  
ORION-GEOSTAR 3 observatories included 3D 
broad-band seismometer with electrochemical 
transducer (PMD EP-300-DT, 0.0167 to 50 Hz 
bandwidth and 100 Hz sampling rate). The 
previously consolidated installation procedure for 
GEOSTAR-class observatories insures a good 
ground coupling of the sensor and signal to noise 
ratio, fundamental requirements to obtain high-
quality seismic recordings [12]. 
 
 
 
Fig. 4. One of the seafloor observatory, namely 
GEOSTAR, on the deck of the R/V Urania before 
the deployment; the observatories are deployed by 
means of a special vehicle, the Mobile Docker 
(MODUS) which is driven from a console on 
board of the ship [4]. All equipment is installed on 
GEOSTAR frame, except from the magnetometers 
that are mounted at the ends of two booms to 
minimize the signatures, on magnetic records, 
induced by the e.m. fields generated by the 
observatory electronics and GEOSTAR frame 
itself. 
 
Noise analysis in the frequency domain was 
performed by calculating the Power Spectral 
Density (PSD) on data segments selected over the 
whole mission period, in absence of earthquake 
signals. The PSD was compared to Peterson’s 
low/high noise models (LNM, HNM) which are 
average spectra computed for broadband 
seismological stations world-wide [13]. An 
example of background noise spectra of seafloor 
seismological recordings taken during the Marsili 
campaign is given in Fig. 5 where the 
corresponding seismogram is also reported (top 
left). The smaller box includes 2500 seconds of the 
three-component signal on which the spectrum was 
calculated. The frequency of 0.2 Hz, typical of 
oceanic microseismic noise, is well defined on all 
the seismic components.  
An interesting aspect of the seismological analysis 
is represented by earthquakes only recorded by the 
seafloor seismometer. They represent about 25% 
of the total local seismicity recorded during the 
Proceedings of the 3rd IASME/WSEAS International Conference on Geology and Seismology (GES’09), pp.153-157                             
ISSN: 1790-2769                                                                                                                           ISBN:978-960-474-058-1 
experiment [14]. Fig. 6 shows an example of an 
earthquake, occurred nearby one of the seafloor 
observatory as testified by the close P-S arrival 
times. In addition, the waveforms of some of the 
events recorded suggest that these might be 
associated to submarine landslides which have a 
duration of some tens of seconds, as we already 
noted in other Mediterranean areas [15]. Some 
attenuation of the body waves was also observed as 
possible indication of hydrothermal circulation 
underneath the Marsili volcano. 
 
 
 
Fig. 5. Power Spectral Density of seafloor seismic 
recordings compared to the Peterson’s noise 
models [13]. 
 
 
 
 
Fig. 6. Example of very local earthquake recorded 
by one of the ORION-GEOSTAR 3 seismometer 
at seafloor. 
The vectorial magnetometer, being a sophisticated 
compass, provided precise information about the 
exact orientation of the benthic station also useful 
for the correct orientation of the seismological 
recordings. From a more scientific viewpoint, the 
study of the time variation of magnetic data 
allowed to estimate conductivity structure 
underneath the area of observations [16, 17, 18]. 
This estimation confirmed the low values of both 
Moho and lithosphere depths as deduced by 
seismic data analysis [7]. 
Fig. 7 shows some examples of geomagnetic 
records: magnetometers are so sensitive that some 
smallish spikes are visible, due to the activation of 
the geochemical package placed in the central 
frame of the benthic station. Functioning 
deterioration of this package caused later on larger 
disturbances on the geomagnetic data: this was an 
important clue to recognise the precise origin of 
the problem. 
 
0000 0200 0400 0600 0800 1000 1200 1400 1600 1800 2000 2200
45500
45550
46300
46350
F 
[n
T]
AUGUST 01, 2004 - Time (UT).  AQU (Dashed line), ORION (Continuous line)
0000 0200 0400 0600 0800 1000 1200 1400 1600 1800 2000 2200
38875
39575
39600
Z 
[n
T]
0000 0200 0400 0600 0800 1000 1200 1400 1600 1800 2000 2200
105
120
18325
18350
18375
Y[
nT
]
0000 0200 0400 0600 0800 1000 1200 1400 1600 1800 2000 2200
24000
24050
27000
27050
 
X 
[n
T]
 
Fig. 7. Example of X, Y, Z, F seafloor magnetic 
field recordings (bold line) and comparison with 
data from L’Aquila Observatory (light line) [18]. 
 
4 Conclusions 
The ORION-GEOSTAR 3 deep seafloor 
experiment was performed from Dec. 2003 to May 
2005 and successfully acquired an enormous 
amount of data. From first data analyses, we found 
interesting geophysical and oceanographic time 
variations occurring around Marsili Volcanic 
Seamount. In particular, magnetic data allow to 
estimate some conductivity structure at different 
depths under the Marsili and gravimetric data show 
relevant signal patterns at low frequency; seismic 
data show some local activity with recurring 
seismic signals. Significant correlations between 
Proceedings of the 3rd IASME/WSEAS International Conference on Geology and Seismology (GES’09), pp.153-157                             
ISSN: 1790-2769                                                                                                                           ISBN:978-960-474-058-1 
recorded time series could be related to activity 
and structure of the Marsili volcano: for instance 
the attenuation of the body waves could be an 
indicator for the possible existence of a 
hydrothermal circuit. This article is a starting point 
for the ambitious endeavour of describing the 
present state of the Marsili Volcanic Seamount. 
 
Acknowledgements 
Other institutions contributed to ORION-GEOSTAR 3: 
Tecnomare S.p.A. and ISMAR-CNR (Italy); TUB, TFH 
and IFM-GEOMAR (Germany); IFREMER and ORCA 
(now SERCEL) (France). Thanks to the Captains and 
the crew of the R/V Urania. Thanks are also due to 
European Commission that funded the project.  
 
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Multiparametric seafloor exploration: the Marsili Basin and Volcanic Seamount case (Tyrrhenian Sea, Italy)

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

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