Vol49_2_2006 659 ANNALS OF GEOPHYSICS, VOL. 49, N. 2/3, April/June 2006 Key words long-term multidisciplinary seafloor ob- servatories – geophysical and environmental seabed monitoring 1. Introduction The European experience on seafloor moni- toring started in early 1990s with the EC MAST (acronyms and abbreviations are listed before the references) Programme. Feasibility studies com- missioned by the EC were addressed to identify- ing the scientific requirements (Thiel et al., 1994) and to establishing the possible technological so- lutions for the development of seafloor observa- tories (ABEL, Berta et al., 1995). In parallel, oth- er studies and activities, such as DESIBEL (Ri- A fleet of multiparameter observatories for geophysical and environmental monitoring at seafloor Paolo Favali (1) (2), Laura Beranzoli (1) , Giuseppe D’Anna (1) , Francesco Gasparoni (3) , Jean Marvaldi (4) , Günther Clauss (5) , Hans W. Gerber (6) , Michel Nicot (7) , Michael P. Marani (8) , Fabiano Gamberi (8) , Claude Millot (9) and Ernst R. Flueh (10) (1) Istituto Nazionale di Geofisica e Vulcanologia, Roma, Italy (2) Università degli Studi di Roma «La Sapienza», Roma, Italy (3) Tecnomare-ENI SpA, Venezia, Italy (4) IFREMER, Centre de Brest, Plouzané, France (5) Technische Universität Berlin, Germany (6) TFH Berlin – University of Applied Sciences, Berlin, Germany (7) SERCEL-Underwater Acoustic Division (former ORCA Instrumentation), Brest, France (8) Istituto di Scienze Marine (ISMAR), CNR, Sezione di Geologia Marina, Bologna, Italy (9) Laboratoire d’Océanographie et de Biogéochimie (LOB), La Seyne-sur-Mer, France (10) IFM-GEOMAR, Kiel, Germany Abstract Seafloor long-term, multiparameter, single-frame observatories have been developed within the framework of European Commission and Italian projects since 1995. A fleet of five seafloor observatories, built-up starting from 1995 within the framework of an effective synergy among research institutes and industries, have carried out a series of long-term sea experiments. The observatories are able to operate from shallow waters to deep-sea, down to 4000 m w.d., and to simultaneously monitor a broad spectrum of geophysical and environmental processes, including seismicity, geomagnetic field variations, water temperature, pressure, salinity, chemistry, currents, and gas occurrence. Moreover, they can transmit data in (near)-real-time that can be integrated with those of the on-land networks. The architecture of the seafloor observatories follows the criteria of modularity, interoperability and standardisation in terms of materials, components and communication protocols. This paper describes the technical features of the observatories, their experiments and data. Mailing address: Dr. Paolo Favali, Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, 00143 Roma, Italy; e-mail: paolofa@ingv.it 660 Paolo Favali et al. gaud et al., 1998), were carried out at EC level, aimed at defining needs and expectations for long-term investigations at abyssal depths. Mean- while, the most technologically advanced coun- tries have launched a large number of projects and programmes addressed to long-term and multi- parameter seafloor monitoring. Favali and Be- ranzoli (2006) review these international efforts. A widely accepted definition of seafloor ob- servatories has progressively been affirmed at numerous international conferences and work- shops (e.g., Chave et al., 1990; Montagner and Lancelot, 1995; Utada et al., 1997; Romano- wicz et al., 2001; Beranzoli et al., 2002; Kasa- hara and Chave, 2003). This definition outlined by NRC (2000) is: « [...] unmanned system of instruments, sen- sors and command modules connected either acoustically or via seafloor junction box to a surface buoy or a cable to land. These observa- tories will have power and communication ca- pabilities [...]». Accordingly, a seafloor observatory is char- acterised by a data acquisition and control sys- Table I. Requirements for the instrumentation used in seafloor observatories. Sensor Typical sampling Data acquisition Installation constraints rates (bits) Three-component 20÷100 Hz 24 – Positioning (error ≤100 m). broad-band seismometer – Orientation to the north (known ≤1°). – Good ground coupling. – Fine levelling (if required). Hydrophone 80 ÷ 100 Hz 24 – Positioning (error ≤100 m). Gravity meter 0.01 ÷ 1 Hz 24 – Positioning. – Temperature controlled. – Fine levelling. Scalar magnetometer 1 sample/min 16 – Minimisation of possible electro-magnetic interferences. Tri-axial fluxgate 1 sample/s 24 – Minimisation of possible electro-magnetic interferences. Precision tilt meter (X, Y) 10 Hz 24 – Northwards orientation. Tri-axial single-point 2 Hz 16 – Avoiding frame interference. current meter ADCP 300 kHz 1 profile/h – Avoiding frame interference. Transmissometer 1 sample/h – Avoiding frame interference. CTD 1 sample/10 min (or 1 sample/h) CH4 sensor 1 Hz 24 H2S sensor 1 sample/10 min 24 (averaged on 30 samples/s) pH sensor 1 sample/6 h (*) – Ampling and self-calibration programmable – Self-calibration every 24 samples (*). Water sampler – 48 bottles, sampling depending on the mission targets. (*) ORION-GEOSTAR-3 configuration. 661 A fleet of multiparameter observatories for geophysical and environmental monitoring at seafloor tem, multiple sensors, long-term autonomy, communication systems, remote re-configura- tion of mission parameters, accurate position- ing. Another important constraint to be consid- ered is a unique time reference for all measure- ments, giving us the chance to compare different processes for exploring possible reciprocal rela- tionships. The sensors themselves are suitable for long-term operation, when properly installed to provide highly reliable data. The require- ments for the instrumentation, used in seafloor observatories, are shown in table I. Between 1995 and 2001 the EC funded the GEOSTAR and GEOSTAR-2 projects (Beran- zoli et al., 1998, 2000a,b; Favali et al., 2002) which designed, developed and operated a pro- totype autonomous deep-sea observatory (here- after GEOSTAR) hosting a wide range of sen- sors in a single frame and providing facilities for external experiments. GEOSTAR satisfied the definition of seafloor observatory men- tioned above with multidisciplinary, long-term monitoring capabilities providing time-refer- enced data series, and the chance to transmit data in (near)-real-time through a surface buoy. Moreover, the management of the observatory from the sea surface has represented an innova- tive approach exportable to other seafloor mon- itoring and survey applications. The GEOSTAR system has performed experiments both in shal- low and deep waters, which confirmed the relia- bility and the feasibility of the deployment/re- covery procedure even in a moderately per- turbed sea state (Jourdain, 1999; Beranzoli et al., 2000a; Favali et al., 2002). Two paths were followed after the GEO- STAR experience: the development of other sin- gle-frame observatories devoted to specific ap- plications and the enhancement of GEOSTAR as principal node of a network of seafloor observa- tories. These paths have led to the current avail- ability of four more GEOSTAR-class observato- ries and the first European prototype of a deep seafloor observatory network. SN-1 and GMM systems were developed (Favali et al., 2004a) among the single-frame GEOSTAR-class observatories. SN-1 is addres- sed to seismological, oceanographic and envi- ronmental measurements developed within a GNDT-funded project (Favali et al., 2003). GMM, built within the EC ASSEM project (Blandin et al., 2003) is devoted to seafloor gas monitoring (Marinaro et al., 2004). Within the framework of the EC ORION- GEOSTAR-3 project (Beranzoli et al., 2004), GEOSTAR was implemented to act as the main node of an underwater network of deep-sea ob- servatories of GEOSTAR-class with the capa- bility of (near)-real-time communication. In ad- dition to this main node, two more observato- ries, with the function of satellite nodes (ORI- ON Nodes 3 and 4), were built and equipped with seismological and oceanographic sensors. The concomitant running of the ORION- GEOSTAR-3 and ASSEM projects has given us the chance to integrate one of the ORION nodes in the shallow water ASSEM system during the ASSEM pilot experiment in Corinth Gulf. This integration has been dedicated to demonstrating the compatibility of the two seafloor networks and the chance to operate a «coast-to-deep-sea» monitoring system in the near future. This paper gives a technical description of the five above-mentioned seafloor observato- ries, together with the presentation of the ac- quired data. A sixth single-frame system, called MABEL, is being developed for polar sea ap- plications within the framework of the Italian PNRA (Calcara et al., 2001). A short descrip- tion of MABEL is also given. 2. The GEOSTAR system GEOSTAR is a single-frame autonomous sea- floor observatory, based on three main sub-sys- tems (Beranzoli et al., 1998): a) the Bottom Sta- tion, that is the monitoring system; b) MODUS, the dedicated deployment/recovery vehicle; c) the Communication Systems. GEOSTAR is ca- pable of long-term (more than one year) multidis- ciplinary monitoring at abyssal depths. At pres- ent, the maximum operative depth is 4000 m. 2.1. Bottom Station The Bottom Station (fig. 1) is a four-leg ma- rine aluminium frame hosting the monitoring system including lithium batteries for power 662 Paolo Favali et al. supply; electronics mounted inside titanium vessels; hard disks for data storage; the under- water part of the communication systems; sci- entific and status sensors. The Bottom Station mission is driven and controlled by a central data acquisition and con- trol unit (named DACS; Gasparoni et al., 2002). GEOSTAR DACS (fig. 2) can perform the fol- lowing tasks: management and acquisition from all scientific packages and status sensors; preparation and continuous update of hourly data messages to be transmitted on request in- cluding detection of events; actuation of re- ceived commands (e.g., data request, system re- configuration, re-start); data back-up on inter- nal memory. DACS manages a wide set of data streams at quite different sampling rates (from 100 Hz to 1 sample/day) tagging each datum according to a unique reference time set by a central high-precision clock (stability within a Fig. 1. GEOSTAR seafloor observatory: Bottom Station with MODUS vehicle on the top. 663 A fleet of multiparameter observatories for geophysical and environmental monitoring at seafloor Fig. 2. DACS equipped with central Bottom Sta- tion high-precision clock (left-bottom) provided by SERCEL (former ORCA Instrumentation). Table II. DACS main technical characteristics of the GEOSTAR-class platforms (e.g., Gasparoni et al., 2002). GEOSTAR SN-1 ORION ORION GMM MABEL(1) Node 3 Node 4 Configuration 4 CPU 3 CPU 3 CPU 3 CPU 1 CPU 2 CPU (MCU, SDU, (MCU, SDU, (MCU, SDU, (MCU, SDU, (MCU, SDU, HDU, DAU) HDU) HDU) HDU) Mass memory 3×8 Gb 3×8 Gb 3×8 Gb 3×8 Gb 512 Mb 30 Gb (2 HDs SDU, (2 HDs SDU, (2 HDs SDU, (2 HDs SDU, (Flash) (HD SDU) 1 HD HDU) 1 HD HDU) 1 HD HDU) 1 HD HDU) 3×64 Mb 1 Gb 3×64 Mb 3×64 Mb 1 Gb (Flash MCU, (Flash MCU) (Flash MCU, (Flash MCU, (Flash MCU) SDU, HDU) SDU, HDU) SDU, HDU) 512 Mb 2×64 Mb 128 Mb (Flash DAU) (Flash SDU, HDU (Flash SDU not used in RTL) Power supply 24 VDC 12 VDC 12 VDC 12 VDC 12 VDC 12 VDC (battery) (battery or cable) (battery) (battery) (battery) (battery) Power 70 mA (ID) 200 mA (ID) 120 mA (ID) 120 mA (ID) 80 mA (ID) < 80 mA (ID) consumption 300 mA (MM) 450 mA (MM) 350 mA (MM) 400 mA (MM) 150 mA (MM) < 200 mA (MM) 550 mA (peak) Communication MODUS (2) MODUS (2) MODUS (2) H acoustics Cable telemetry MODUS (2) interfaces V acoustics V acoustics H acoustics V acoustics H acoustics Fibre-optic MESSENGERS telemetry (1) The first polar experiment started at the end of 2005; (2) during deployment. MCU – Mission Control Unit; SDU – Seismometer Data acquisition Unit; HDU – Hydrophone Data acquisition Unit; DAU – Data Acquisition Unit; HD – Hard Disk; RTL – Real Time Link [mode]; ID – Idle mode: all sensors switched off; CPUs waiting command from the operator; MM – Mission Mode: all sensors switched on; CPUs and communications active; V – Vertical; H – Horizontal. range 10–9 to 10–11, accordingly to supplier spec- ifications and verified during the experiments controlling the clock drift). The sensors were selected also in order to keep power consump- tion lower than 350 mA at 24 V. Table II de- scribes the GEOSTAR DACS’ main technical characteristics. Devices were designed and im- plemented to install the seismometer and mag- netometers with the aim of reducing the distur- bances caused by the observatory frame and electronics. The former, installed in a benthos- phere by the supplier, was included inside a heavy cylindrical housing. Then the whole package was released by a special device after the Bottom Station touch down to guarantee a good coupling with the sea bottom, and was kept linked to the Bottom Station frame by a 664 Paolo Favali et al. slack rope. Special care was taken in the choice of the electronic components of the INGV flux- gate magnetometer prototype. The resolution of this prototype is 1 nT and an absolute accuracy 5 nT. The magnetometers, used in the early ver- sion, were scalar (Overhauser magnetometer) and bi-axial fluxgate (horizontal axes), then in all the subsequent experiments the INGV flux- gate prototype was fully tri-axial. They were in- stalled at the end of two booms attached at op- posite angles of the Bottom Station frame to keep them as far as possible from electronic noise sources. The booms, kept vertical during the descent, were opened by command from the surface through the umbilical cable, once the observatory was placed on the seafloor. The di- rection of the three components of the geomag- netic field was reconstructed using the scalar in- formation (total field) deduced from the Over- hauser magnetometer and from calibrating the fluxgate magnetometer in the air close to the Geomagnetic Observatory of L’Aquila (Central Italy). The results were also confirmed when compared with the horizontal component as de- duced from a land magnetic station running dur- ing the first deep mission close to Ustica Island (Sicily, Italy) in 2000-2001 (see also De Santis et al., 2006). 2.2. MODUS MODUS, a simplified ROV, is the special vehicle for the deployment/recovery procedures (Clauss and Hoog, 2002; Clauss et al., 2004; Gerber and Clauss, 2005). MODUS is remotely controlled from the ship through a dedicated electro-opto-mechanical cable. The telemetry system also provides the primary communica- tion link with the observatory during the de- ployment phase. It is equipped with a latch/re- lease device and thrusters mounted on a frame around the cone that assists the docking. The aim is to load, deploy and recover the Bottom Station in surface-assisted mode. The MODUS frame is also equipped with video cameras for visual seabed inspection, compass, sonar and altimeter. The main MODUS characteristics are listed in table III, while the system is shown in fig. 3a-e including the latch/release scheme. Table IV contains the main features of the han- dling system (winch, hydraulic unit and sheave) and cable (fig. 4). 2.3. Communications systems Two independent Communication Systems were originally developed for GEOSTAR, based on different principles (Marvaldi et al., 2002). The first one consists of buoyant data capsules, named MESSENGERS, releasable upon surface command or automatically, when full of data or in case of emergency. Two types of MESSENGERS are available: a) expendable (data storage capacity 64 Kb); b) storage (data stor- age capacity larger than the expandable, 40 Mb). They can transmit their position at sea sur- face and small quantities of data via ARGOS satellites. The second communication system is based on a bi-directional vertical acoustic link Table III. MODUS main characteristics (Clauss and Hoog, 2002; Clauss et al., 2004; Gerber and Clauss, 2005). Purpose Umbilical-driven frequent operations Material Aluminium (frame) Stainless steel (docking device) Titanium (pressure vessels) Weight in air (kN) 10 Weight in water (kN) 7 Total length-L (m) 2878 Total width-W (m) 2348 Total height-H without cable 1700 termination (m) Maximum payload (kN) 30 Power (kW) 25 Horizontal thrusters (N) 4×700 Vertical thrusters (N) 2×700 Altimeter range (m) 100 Heading accuracy (degrees) 1 Tilt accuracy (degrees) 1 360° sonar range (m) 300 Video cameras (+ lights) 6 Videos and recorders 4 Depth rated (m) 4000 665 A fleet of multiparameter observatories for geophysical and environmental monitoring at seafloor Fig. 3a-e. MODUS, the GEOSTAR deployment/recovery vehicle: a) docking cone and b) pin; c) MODUS on the deck of R/V Urania; d) MODUS on-board console; e) Bottom Station signature displayed on the sonar monitor. Table IV. Main characteristics of the winch (MacArtney) and cable (Rochester). Item Dimensions (m) Weight (kN) Max payout Load (kN) Max pull (kN) Notes speed (m/min) Winch 3.80×2.35×2.40 181 70 (a) 80 (c) 102 (a) −20 ÷ + 45°C (L×W×H) 51 (b) 75 (b) Remote control HPU (1) 1.77×1.15×1.71 20 325 bar (L×W×H) 75 kW (3×380 V-50 Hz) Sheave 1.05 (Ø) 0.2 100 (d) Instrumented (cable out, pull, speed) Cable 0.0254 (Ø) 22 (e) (in air) 89 (d) 3 optic fibres 4000 (length) 18 (e) (in water) 205 (f) 3×3000 VAC-6A (1) Hydraulic Pump Unit; (a) 1st layer; (b) 10th layer; (c) static, top layer; (d) working load; (e) kN/km; (f) break- ing strength. a b c d e 666 Paolo Favali et al. Fig. 4. The GEOSTAR handling system: power unit (right), cable spooled on the winch (left) and system con- sole (insert) . Fig. 5a-d. a) MESSENGERS installed on the Bottom Station (height 1.3 m); b) MESSENGERS Storage and Expend- able-type in Brest IFREMER Laboratory; c) surface buoy (weight: 35 kN; volume: 5 m3) GEOSTAR-2 version on board R/V Urania; d) surface buoy ORION-GEOSTAR-3 version just deployed. a b c d 667 A fleet of multiparameter observatories for geophysical and environmental monitoring at seafloor with a ship of opportunity or moored buoy, called MATS-12 (frequency: 12 kHz; speed: up to 2400 bit/s). A surface relay buoy, equipped with a surface telemetry unit and radio/satellite transmitters, assures the (near)-real-time com- munication between a shore station and the ob- servatory on the seafloor. Pictures of the MES- SENGERS and the buoy are shown in fig. 5a-d. 3. Single-frame systems derived from GEOSTAR 3.1. SN-1 SN-1 is a reduced-size version of GEO-STAR (fig. 6) and represents the recent effort of Italian marine research and technology addressed to the Fig. 6. SN-1 and MODUS (left) on the deck of the cable-vessel Pertinacia before deployment; the ROV connect- ing SN-1 Observatory to the cable interface (top-right); SN-1 on the seafloor during the cable connecting operations (bottom-right). The cable route from Catania harbour to 25-km east in the Ionian Sea is shown in top-left panel. 668 Paolo Favali et al. development of a seafloor network around Italy (Favali and Beranzoli, 2006). SN-1 has the same features as GEOSTAR in regard to deployment/ recovery procedures based on MODUS, the data acquisition system (SN-1 DACS, see table II) and the special device for seismometer installation developed in the GEOSTAR projects (see Section 5 for details). Compared with GEOSTAR, SN-1 hosts a reduced set of sensors, mainly seismolog- ical and oceanographic. Like GEOSTAR, SN-1 has a vertical acoustic link from the seafloor to a surface unit managed by a ship of opportunity, while it is not supported by a surface-moored buoy. From October 2002 to May 2003 SN-1 suc- cessfully completed the first long-term experi- ment off-shore from Catania (Southern Italy, Eastern Sicily) at 2105 m w.d. in autonomous mode (Favali et al., 2003). After this experiment, SN-1 was fitted with a fibre-optic telemetry interface so as to be com- patible with the electro-optical cable owned and deployed off-shore from Catania by INFN. In January 2005, the observatory was deployed at the same site as the first mission (about 25 km East from Catania at 2060 m w.d.) by MODUS and connected to the submarine cable. The sea operations were carried out using the C/V Perti- nacia (Elettra Tlc SpA) and the SN-1 connection was performed by the on-board deep-rated ROV. SN-1 receives power from the shore, can com- municate in real-time with the shore station lo- cated in the LNS-INFN laboratory inside Catania harbour, and is integrated in the INGV land- based networks. SN-1 is the first real-time sea- floor observatory in Europe and one of the few in the world. It is also the first seafloor observatory operative in one of the «key-sites» planned in the EC project ESONET (Priede et al., 2003, 2004). These achievements were fulfilled thanks to a MoU between INGV and INFN, which is going to use the site for the NEMO pilot experiment ad- dressed to the underwater detection of neutrinos (Favali et al., 2003; Favali and Beranzoli, 2006). 3.2. GMM Designed and built within the framework of the ASSEM project (Blandin et al., 2003), GMM is another system developed on the basis of the GEOSTAR experience (Marinaro et al., 2004). GMM is an autonomous station de- signed to monitor the gas seawater concentra- tion close to the seabed. GMM is based on a light benthic circular tripod of aluminium alloy (fig. 7). It can also operate interfaced to exter- nal units (e.g., other seafloor nodes of an under- water network, on-shore stations) via a subma- rine cable. The system can be reconfigured ei- ther to be integrated in more complex observa- tories (like GEOSTAR) or operated as a pay- load of submarine vehicles for surveys. In par- ticular, the GMM design allows for modifica- tion of the frame-top and the installation of the mechanical interface to be managed during de- ployment/recovery procedures by MODUS. GMM electronics performs similar tasks as the GEOSTAR DACS (see table II). Fig. 7. GMM module on the ship before the de- ployment in the Corinth Gulf. 669 A fleet of multiparameter observatories for geophysical and environmental monitoring at seafloor 3.3. MABEL MABEL is another deep-sea multiparame- ter seafloor observatory under development specifically addressed to the acquisition of geo- physical, geochemical, oceanographic and en- vironmental time series in polar regions (Cal- cara et al., 2001). MABEL, sponsored by the Italian PNRA, is designed to operate au- tonomously for at least one year and will be the first seafloor observatory deployed in Antarcti- ca. The characteristics of its DACS are shown in table II. Its mechanical and electronic behav- iour at low temperatures was already tested in 2002 at HSVA Basin (Hamburg) in simulated polar conditions (air: −15°C, and icy waters: −2°C) (fig. 8; Cenedese et al., 2004). The first Antarctic MABEL experiment started at the end of the 2005 having deployed the observato- ry in the Weddell Sea at over 1800 m w.d., with the logistic support of the R/V Polarstern man- aged by AWI, and it will last for at least one year. 4. ORION-GEOSTAR-3 system Within the framework of the EC ORION- GEOSTAR-3 project, the GEOSTAR Bottom Station, the surface relay buoy and MODUS have been upgraded in order to be able to man- age a network of GEOSTAR-class observato- ries, as a significant step towards deep-sea net- working (Beranzoli et al., 2004). Two addition- al observatories have been developed (ORION Nodes 3 and 4) being able to communicate via acoustics with GEOSTAR Bottom Station. The communication system has been implemented in order to enable the GEOSTAR Observatory to operate as the main node (gateway) of the ORION network, exchanging data and status parameters with the satellite nodes and transfer- ring data to the sea surface. A picture with the general scheme of ORION-GEOSTAR-3 is shown in fig. 9. The Bottom Station has thus also been equipped with horizontal acoustics devoted to the communication among the nodes, based on MATS modems. Through the horizontal com- munication, GEOSTAR receives automatic messages from the satellite nodes, while the vertical communication to the surface buoy, en- hanced with respect to the original version, is used to transmit data from both GEOSTAR and the nodes. Connection between the buoy and a shore station is ensured by radio and satellite links. Data, specifically pieces of seismic wave- forms, can be retrieved on request. The horizon- tal modems use omni-directional transducers, whereas the vertical acoustic link is based on directional transducers. The buoy transmission system (DRTS) comprises an electronic unit (MEU) managing the communications and in- terfacing the acoustic transmission system with two buoy-to-shore data links, VHF radio or IRIDIUM satellite. In case of VHF-link failure, a switch to the satellite transmission is automat- ically performed. Fig. 8. MABEL during the low temperature tests at HSVA Basin in Hamburg. 670 Paolo Favali et al. To achieve the new required functionality, the DACS has been properly enhanced (Beran- zoli et al., 2004). The sampling rate of some sensors (e.g., gravity meter) has been increased and new sensor packages installed (e.g., elec- trode analyser, hydrophone). Accordingly, addi- tional acquisition channels have been made available. The following function was imple- mented: automatic event detection on the seis- mometer and hydrophone data, transmission of seismometer waveforms. The DACS interface to the communication system was properly en- Fig. 9. Scheme of management and operation of the ORION-GEOSTAR-3 deep-sea network of GEOSTAR- class seafloor observatories. Table V. List of the GEOSTAR-class platforms and some specifications. Platform Overall dimensions (m) Weight (kN) Weight (kN) Depth rated (m) (L×W×H) (in air) (in water) GEOSTAR 3.50×3.50×3.30 25.4 14.2 4000 SN-1 2.90×2.90×2.90 14.0 8.5 4000 ORION Node 3 2.90×2.90×2.90 14.0 8.5 4000 ORION Node 4 2.00×2.00×2.00 6.6 3.4 1000 GMM 1.50×1.50×1.50 1.5 0.7 1000 MABEL 2.90×2.90×2.90 14.0 8.5 4000 671 A fleet of multiparameter observatories for geophysical and environmental monitoring at seafloor hanced in order to make data and status param- eter available for transmission to the communi- cations system. The communications can be started by any of the ORION-GEOSTAR-3 net- work nodes. The DACS hardware has been also upgraded in order to increase functions/capabil- ities and reliability with reduced power and vol- ume requirements (see table II): a) new CPU boards with increased power; b) new status boards with additional sensors, scientific data acquired at 24 bits; c) status sensors acquired at 16 bits (12 bits in the previous version); d) boards managing up to 32 Gb on hard disk and 1 Gbyte on flash card (see table II). As already mentioned, the EC requested the ORION-GEOSTAR-3 and ASSEM networks to be compatible. Accordingly, common commu- nication protocols were defined and implement- ed in the nodes of both networks in regard to data communication. For this purpose, an ORI- ON node (Node 4) was deployed and tested to- gether with the ASSEM nodes in the Corinth Gulf pilot experiment. The list of the GEOSTAR-class platforms with some specifications are summarised in table V. 5. Experiments, data and prototyping activity The sea experiments performed are depicted in table VI including specific information and the sensors used in each experiment. Figure 10 shows the map of the locations. All the experi- ments were carried out by means of medium- size vessels with dGPS and DP, like, for in- stance, the CNR R/V Urania. Only for the de- ployment of SN-1 and its connection to the electro-optical cable was a larger cable vessel used (C/V Pertinacia). GEOSTAR performed its first sea demon- stration mission in shallow waters in 1998 (Jour- dain, 1999; Beranzoli et al., 2000a,b). The obser- vatory was deployed on the seafloor of the Adri- atic Sea (Northern Italy) about 50-km east of Ravenna harbour. The selection of the mission site was based both on the knowledge of geolog- ical and geotechnical soil characteristics (flat and consolidated seabed, distance from turbulence sources, absence of pockmarks and gassy sedi- ments) and safety factors (shallow water depth, vicinity to harbour logistics). The starting mis- sion procedure foresaw that after the Bottom Sta- tion had touched down, all the sensor packages and devices were switched on through MODUS telemetry and their correct functioning was checked. After the positive outcome of this oper- ation, the Bottom Station was released by MODUS and left on the sea bottom (Beranzoli et al., 2000a,b). During the shallow water demo mission around 346 Mb of data were acquired over roughly 440 operational hours, correspon- ding to 98% of the mission’s duration, see table VI for the list of the used sensors. An expandable MESSENGER was automatically released and transmitted data via the ARGOS satellite. A stor- age MESSENGER was release acoustically just be- fore the Bottom Station’s recovery. The experi- ment demonstrated the functionality of the whole system, including MODUS. Temporary magnetic and seismological stations were also installed on land as a reference for GEOSTAR measurements. Analysis of data acquired, even if during only 21 days, pointed out the reliability of the measurements and their scientific potentiali- ty as a unique time-referenced multiparameter data. Some interesting events, like regional earthquakes, water current and thermocline depth variations, and a magnetic storm were recorded (Beranzoli et al., 2003). The first GEOSTAR long-term deep-sea mis- sion was performed between September 2000 and April 2001 at about 2000 m w.d. in Southern Tyrrhenian Sea (see table VI). The communica- tion system was enhanced adding a surface moored buoy, equipped with the interface of the acoustic system and a radio/satellite link for (near)-real-time transmission between the Bot- tom Station and on-shore sites. Data acquired, 4160 h corresponding to about 174 days (out of 205 because the batteries were exhausted), amount to more than 65 Mb mostly from the gravity meter. An external self-recording hydro- phone acquired 4 Gb of data. Also in this long- term experiment, the data quality was high, as demonstrated by De Santis et al. (2006), Iafolla et al. (2006), and Etiope et al. (2006) pointed out ocean-lithosphere interactions at BBL level. During the 2002-2003 experiment off-shore from Catania (Southern Italy, Eastern Sicily; 672 Table VI. List of the seafloor experiments performed with GEOSTAR-class platforms and the sensors used (see fig. 10 for the map). Experiments Location Depth Year(s) Days Platform(s) Sensors used (m) GEOSTAR Northern Adriatic 42 1998 21 GEOSTAR Three-component broad-band (demo mission) Sea (Italy) seismometer; scalar magnetometer; fluxgate magnetometer (only X-Y); ADCP 300 kHz; CTD; transmis- someter; precision tilt meter (X, Y). GEOSTAR-2 (1) Southern Tyrrhenian 1950 2000 205 GEOSTAR Gravity meter; scalar magnetometer; (1st deep-sea Sea (Italy) 2001 tri-axial fluxgate magnetometer; mission) ADCP 300 kHz; CTD; transmis- someter; tri-axial single-point cur- rent meter; precision tilt meter (X, Y); water sampler (off-line); hydrophone (off-line). (2) SN-1 Western Ionian Sea 2105 2002 213 SN-1 Three-components broad-band (first mission) (off-Eastern Sicily, 2003 seismometer; hydrophone; gravity Italy) meter; CTD; tri-axial single-point current meter. ASSEM Gulf of Patras 40 2004 198 (3) GMM CH4 sensors (3); H2S sensor; CTD. (pilot experiment, (Greece) 2005 in a pockmark) ASSEM Gulf of Corinth 380 2004 214 ORION Three-component broad-band (pilot experiment) (Greece) Node 4 seismometer; hydrophone; (ORION-GEO- CH4 sensor. STAR-3 -ASSEM clustering) ORION-GEO Tyrrhenian Sea 3320 2003 477(4) GEOSTAR (G) Three-comp. broad-band STAR-3 (deep- (Marsili seamount, 2005 and ORION seismometers (G, N3); sea networking) Italy) Node 3 (N3) hydrophones (G, N3); gravity meter (G); scalar magnetometer (G); tri-axial fluxgate magnetometer (G); ADCP 300 kHz (G); CTD (G); transmissometer (G); tri-axial single- point current meter (G); pH sensor (G); precision tilt meter (X, Y) (G); water sampler (off-line) (G). NEMO – SN-1 Western Ionian Sea 2060 2005 Ongoing SN-1 Three-component broad-band (cabled January (off-Eastern Sicily, seismometer (5); hydrophone; 25, 2005) Italy) gravity meter; scalar magnetometer; CTD; tri-axial single-point current meter. (1) This experiment included originally also a three-component broad-band seismometer and a chemical analyser prototype. These instruments were not used in the experiment, due to failures that occurred during the sea opera- tions preceding deployment; (2) provided by IFM-GEOMAR; (3) 91days from April 26 to July 26, 2004, and 107 days from September 29, 2004 to January 14, 2005; (4) 134 days from December 14, 2003 to April 26, 2004, and 337 days from June 14, 2004 to May 23, 2005; (5) installed in a titanium sphere. Paolo Favali et al. 673 A fleet of multiparameter observatories for geophysical and environmental monitoring at seafloor table VI), SN-1 acquired in autonomous mode, around 10 Gb of data, 7.65 Gb of which belong to 100 Hz sampling rate broad-band seismome- ter, Guralp CMG-1T (Favali et al., 2003). The double housings of seismometer, comprising a ti- tanium benthosphere inside an external bell, and the relative simple procedure to release it allowed protection from sea-current effects and good cou- pling of the instrument to the seabed. These solu- tions, already used in the previous GEOSTAR experiments, were validated and allowed to col- lect high-quality seismological data (Monna et al., 2005). The signals showed noise in the un- derwater environment (Webb, 1998) with a level comparable with «quiet» terrestrial seismic sta- tions, well within the high and low background noise reference models (Peterson, 1993). It is worth noting that in our case, unlike the ocean experiments, long-period noise on the vertical component caused by infragravity waves is not a first-order effect. In fact, the energy of infragrav- ity waves in the Mediterranean Sea is small as compared with the Pacific and Atlantic oceans. Thanks to its good S/N ratio SN-1 demonstrated the relevant improvement of the seismic event detection recording hundreds of local events not recorded by the dense on-land networks (Favali et al., 2004b). Examples of the data collected are shown in fig. 11a-f. GMM was deployed in an active pockmark in the Gulf of Patras (Corinth Shelf, Greece) in April 2004 as one of the nodes of the ASSEM system (see table VI). The system was simply lowered down to the seafloor (40 m w.d.) with a mechanical cable and positioned in the right place by divers. GMM was linked to a subma- rine cable for real-time data transmission to an on-shore modem. The 12 V, 960 Ah lithium bat- tery pack made six-month autonomous opera- tion possible. A remote link to the on-shore mo- dem was active for the system checks and data retrieval. Through this daily link, a malfunc- tioning in all of the methane sensors was detect- ed at the end of July, so the system was recov- ered at the end of September, the CH4 and H2S sensors were replaced, and the mission re-start- ed after one day. GMM was operating until mid-January 2005. Data analysis is in progress. Fig. 10. Map of the seafloor experiments performed with GEOSTAR-class platforms, see table VI for details. 674 Paolo Favali et al. The first long-term mission of the ORION- GEOSTAR-3 deep-sea network started in De- cember 2003 (see table VI and fig. 12). The de- ployment site lies in the Southern Tyrrhenian Sea at more than 3300 m w.d. at the NW base of the Marsili complex volcanic seamount, one of the largest seamounts of the Mediterranean Basin (Marani et al., 2004). The network con- figuration for this mission includes GEOSTAR as main node and one satellite (ORION Node 3) in horizontal acoustic communication with GEOSTAR deployed 1 km apart. A surface buoy enables the connection with GEOSTAR via vertical acoustics and the radio/satellite link with the on-shore station located at the INGV observatory of Gibilmanna (northern coast of Sicily). Due to a malfunctioning in the acoustic communication link with the nodes (underwater Fig. 11a-f. SN-1 measurements acquired in Ionian Sea at over 2000 m w.d. in stand-alone mode (first mission, 2002-2003) and in real-time acquisition mode (cable connected, since end of January 2005): a) regional earth- quake of 27 December 2002, not reported by land-network bulletins, showing P-, S-, and T-phase arrivals; b) 2002-2003 Mt. Etna eruption, seismic activity of the volcano over one hour (27 October, 2002, 2:00-3:00 a.m.), including the major event of the sequence (ML = 4.8); c) temperature measured by CTD sensor over the mission period (the mean value is around 13.74°C); d) teleseism occurred in Kuril Islands (Mw = 7.3) and recorded by the gravity meter on 17 November, 2002; e) water current velocity components over the mission period, the N-S component, running along the Sicilian coast from/to the Messina Strait shows the most significant values (in av- erage 5 cm/s); f) real-time acquired waveforms of the 28 March, 2005 Sumatra earthquake (Mw = 8.7). a c e b d f 675 A fleet of multiparameter observatories for geophysical and environmental monitoring at seafloor part), they were recovered at the end of April 2004 and re-deployed at the same site at the middle of June until the final recovery in May 2005, always using the R/V Urania. Examples of the collected data are shown in fig. 13a-d. Parallel to sea experiments with the GEO- STAR-class platforms, sensor prototypes also had to be developed, due to the lack of reliable instruments to collect long-time data series es- pecially in the deep-sea environment. A fluxgate magnetometer (first version bi-axial, then tri-ax- ial) built at INGV and subsequently manufac- tured industrially by Tecnomare (a company of Eni Group) has been successfully used since GEOSTAR demo mission. Its resolution is 0.1 nT, the absolute accuracy 5 nT, and the power consumption reduced to 2 W. The thermal drift of the three-component magnetometer (0.2-0.5 nT/°C for typical fluxgate magnetometers) is expected to be negligible because the sea tem- perature is quite constant at the working depths of more than 2000 m, within a fraction of 1°C. Another prototype is a gravity meter derived from a prototype built for space applications, its marine version was developed in a joint venture between INGV and IFSI-INAF, and has been successfully used since GEOSTAR-2’s first deep-sea mission in the Tyrrhenian Sea. The main characteristics of the gravity meter are sensitivity 10−9 g Hz−1/2; frequency range 10−5 to 10−1 Hz; power consumption 300 mW; volume 10 cm3; weight 2 kg (Iafolla and Nozzoli, 2002). The last prototype developed and tested both in the laboratory and in the deep- sea (in the ORI- ON-GEOSTAR-3 project) is an automatic elec- trode analyser. This analyser with self-calibrat- ing capability is capable of performing long- term (six months) experiments. The instrument was developed and validated in a joint activity between INGV and Tecnomare. At present, it is equipped with a pH electrode (AMT), which is the only commercially electrode for the deep- sea, but it can be equipped with other elec- trodes. The main characteristics of pH electrode Fig. 12. GEOSTAR gateway seafloor observatory (right) and ORION Node 3 (left) on the deck of the R/V Ura- nia before the deployment at the base of Marsili underwater volcano (ORION-GEOSTAR-3 first mission). 676 Paolo Favali et al. are in pH units: range 2 to 11; accuracy 0.05; resolution 0.01. The electrode can operate at the maximum pressure of 600 bar, and at a T range from −2 to +38°C. All these prototypes are man- aged by the DACS. Other sensors, like a nuclear spectrometer, are undergoing development. 6. Conclusions GEOSTAR, derived platforms and the ORI- ON-GEOSTAR-3 deep-sea observatory net- work, have been tested during long-term mis- sions (maximum duration over 330 days). The assets of these platforms lie in the reliability of the whole system, the chance to have (near)-real- time communications, and the data quality. The chance to perform quick comparisons of unique time-referenced data series of different sensors makes the development of multiparameter data analysis quite easy. The GEOSTAR-class plat- forms represent a fleet of five seafloor observa- tories among the twenty-eight available world- wide already validated at sea (Favali and Beran- zoli, 2006). These platforms are perfectly com- patible and can be easily re-configured according to the specific applications. All these features fit the requirements outlined within the framework of specific programmes, such as the ESA-EU GMES joint programme. Fig. 13a-d. ORION network measurements acquired at the base of the Marsili seamount: a) one month of mag- netometer measurements (April 2004, red line) compared with the Italian land reference observatory (L’Aquila) in Central Italy; b) pH measurements by the electrode analyser compared with the chemical analysis (Stronzi- um) performed on the samples collected by the water sampler; c) local event of the Southern Tyrrhenian Sea (3 March 2004, ML = 4.6) recorded by the seismometer; d) teleseismic event recorded by the gravity meter (26 De- cember 2003, MS = 6.8, Iran). a b c d 677 A fleet of multiparameter observatories for geophysical and environmental monitoring at seafloor Acknowledgements First of all, we are deeply indebted to the EC that supported our activities and funded many projects within the framework of the MAST and the Environment Programmes. The Authors also wish to thank everyone who worked in the European and Italian proj- ects (A) GEOSTAR (EC), (B) GEOSTAR-2 (EC), (C) ASSEM (EC), (D) ORION-GEO- STAR-3 (EC), (E) SN-1 (GNDT), (F) MABEL (PNRA): INGV (co-ordinator: A, B, D, E and F; part- ner: C): Laura Beranzoli, Thomas Braun, Lili Cafarella, Massimo Calcara, Paolo Casale, Giuseppe D’Anna, Roberto D’Anna, Angelo De Santis, Domenico Di Mauro, Manuela Dit- ta, Giuseppe Etiope, Paolo Favali, Francesco Frugoni, Louis Gaya-Pique, Matteo Grimaldi, Cristina La Fratta, Nadia Lo Bue, Luigi Inno- cenzi, Luigi Magno, Giuditta Marinaro, Sabrina Mercuri (till 2003), Caterina Montuori, Stephen Monna, Paolo Palangio, Giuseppe Passafiume, Giovanni Romeo, Stefano Speciale, Tiziana Sgroi, Giuseppe Smriglio, Roberto Tardini, Ro- berta Tozzi. ISMAR-CNR (partner: A, B, D and E): Fa- biano Gamberi, Michael P. Marani. Tecnomare SpA (partner: A, B, D, E and F; sub-contractor: C): Marco Berta (up to 1997), Ercole Boatto, Gian Mario Bozzo (till 2000), Daniele Calore (till 2004), Renato Campaci, Ste- fano Cenedese, Roman Chomicz, Felice Da Prat, Flavio Furlan, Francesco Gasparoni, Mascia Lazzarini, Andrea Marigo (till 1998), Luciano Pedrocchi, Carmelo Pennino (up to 1997), Wal- ter Prendin, Fabio Zanon, Marco Zordan (till 2002). TUB (partner: A, B, D, E and F): Günther Clauss, Haiko de Vries, Sven Hoog (till 2004), Jorg Kruppa, Peter Longerich. TFH (partner: A, B, D, E and F): Hans W. Gerber, Wilfried Langner. IFREMER (co-ordinator: C; partner: A, B and D): Yannick Aoustin, Jérôme Blandin, Gérard Guyader, Yvon Le Guen, David Le Piv- er, Gérard Loaëc, Jean Marvaldi, Roland Per- son, Christian Podeur, Jean-Francois Rolin. LOB-CNRS (partner: A and B): Jean-Luc Fuda, Claude Millot, Gilles Rougier. SERCEL-Underwater Acoustic Division, former ORCA Instrumentation (partner: A, B and D; sub-contractor: C): Gerard Ayela, Domi- nique Barbot, David Fellmann (till 2002), Jean- Michel Coudeville, Michel Nicot, Alain Priou. IFSI-INAF (partner: E; sub-contractor: B and D): Emiliano Fiorenza (till 2004), Valerio Iafolla, Vadim Milyukov, Sergio Nozzoli, Mat- teo Ravenna. IPGP (partner: B and C): Pierre Briole, Jean- Paul Montagner. IFM-GEOMAR (partner: D): Joerg Bialas, Ernst R. Flueh. OGS (partner: E and F): Renzo Mosetti, Marino Russi. HCMR (partner: C): Vasilios Lykousis. University of Patras (partner: C): Dimitris Christodoulou, George Ferentinos, George Pap- atheodorou. CAPSUM Technologie GmbH (partner: C): Michel Masson. NGI (partner: C): Per Sparrevik, James M. Strout. FUGRO Engineers (partner: C): David Cathie. University of Roma-3 (partner: E): Andrea Billi, Claudio Faccenna. University of Catania (partner: E): Stefano Gresta. University of Messina (partner: E): Giancar- lo Neri. University of Palermo (partner: E): Dario Luzio. Special thanks to: Claudio Viezzoli and Mar- cantonio Lagalante (marine logistics); Capts. Emanuele Gentile and Vincenzo Lubrano, and the crew of R/V Urania, vessel owned by CNR and managed by So.Pro.Mar.; Capt. Alfio Di Gi- acomo and the crew of M/P Mazzarò, vessel owned by Gestione Pontoni SpA; Capt. Vincen- zo Primo and the crew of C/V Pertinacia, owned by Elettra Tlc SpA (Giuseppe Maugeri, chief of mission). The authors are very grateful to the review- ers for their comments able to greatly improve the clarity and quality of the paper. This paper is dedicated to the memory of Luc Floury and Giuseppe Smriglio, who em- barked on this adventure many years ago, be- lieving in the potential of this «new» Science. 678 Paolo Favali et al. List of acronyms and abbreviations used in the text ABEL – Abyssal BEnthic Laboratory. ADCP – Acoustic Doppler Current Profiler. ARGOS – Advanced Research and Global Observation Satellite (WWW site: http://www.cls.fr/html/argos/ welcome_en.html). ASSEM – Array of Sensors for long-term SEabed Monitor- ing of geo-hazards (WWW site: http://www.ifremer.fr/ assem). AWI – Alfred-Wegener-Institut für Polar- und Meeresfor- schung (WWW site: http://www.awi-bremerhaven.de). BBL – Benthic Boundary Layer. CNR – Consiglio Nazionale delle Ricerche (http://www.cnr.it) CNRS – Centre National de la Recherche Scientifique (WWW site: http://www.cnrs.fr). CTD – Conductivity, Temperature and Depth. C/V – Cable Vessel. DACS – Data Acquisition and Control System. DESIBEL – DEep-Sea Intervention on future BEnthic Lab- oratory (WWW site: http://dbs.cordis.lu/cordis-cgi/ srchidadb?caller=projadvancedsrch&srch&qf_ep_ rcn_a =27267&action=d). dGPS – Differential Global Positioning System (WWW site: http://chartmaker.ncd.noaa.gov/staff/dgps.htm). DP – Dynamic Positioning. DRTS – Data Radio Transmission System. EC – European Commission (WWW site: http://europa.eu.int/ comm). ENI – Ente Nazionale Idrocarburi (WWW site: http:// www.eni.it). ESA – European Space Agency (WWW site: http:// www.esa.int). ESONET – European Seafloor Observatory NETwork (WWW site: http://www.abdn.ac.uk/ecosystem/esonet). EU – European Union (WWW site: http://europa.eu.int). GEOSTAR – GEophysical and Oceanographic STation for Abyssal Research (WWW site: http://www.ingv.it/ geostar/geost.htm) GEOSTAR-2 – GEOSTAR 2nd Phase: deep-sea mission (WWW site: http://www.ingv.it/geostar/geost2.htm). GMM – Gas Monitoring Module (WWW site: http:// www.ifremer.fr/assem/corinth/photo_gallery/photo_ gallery.htm). GMES – Global Monitoring for Environment and Security (WWW site: http://www.gmes.info). GNDT – Gruppo Nazionale per la Difesa dai Terremoti (WWW site: http://gndt.ingv.it). HCMR – Hellenic Centre for Marine Research (WWW site: http://www.hcmr.gr). HSVA – Hamburgische Schiffbau-VersuchsAnstalt GmbH (WWW site: http://www.hsva.de). IFM-GEOMAR – Leibniz-Institut für Meereswissen- schaften an der Universität Kiel (WWW site: http:// www.ifm-geomar.de). IFREMER – Institut Français de Recherche pour l’Exploita- tion de la Mer (WWW site: http://www.ifremer.fr). IFSI-INAF – Istituto di Fisica dello Spazio Interplanetario- Istituto Nazionale di Astrofisica (WWW site: http:// www.inaf.it). INFN – Istituto Nazionale di Fisica Nucleare (WWW site: http://www.infn.it). INGV – Istituto Nazionale di Geofisica e Vulcanologia (WWW site: http://www.ingv.it). IPGP – Institut de Physique du Globe de Paris (WWW site: http://www.ipgp.jussieu.fr). ISMAR – Istituto di Scienze Marine-CNR, Sezione di Geologia Marina di Bologna (WWW site: http:// www.bo.ismar.cnr.it). LNS – Laboratori Nazionali del Sud (WWW site: http:// www.lns.infn.it). LOB – Laboratoire d’Océanologie et de Biogéochemie (WWW site: http://www.com.univ-mrs.fr/lob). MABEL – Multidisciplinary Antarctic BEnthic Laboratory (WWW site: http://www.ingv.it/geostar/mabel.html). MAST – MArine Science and Technology (WWW site: http://www.cor-dis.lu/mast). MATS-12 – Multimodulation Acoustic Transmission Sys- tem-12 kHz (WWW site: http://www.sercel.fr). MEU – Multipurpose Electronic Unit. MODUS – MObile Docker for Underwater Sciences MoU – Memorandum of Understanding. M/P – Moto Pontoon. NEMO – NEutrino Mediterranean Observatory (WWW site: http://nemoweb.lns.infn). NGI – Norges Geotekniske Institutt (WWW site: http:// www.ngi.no). NRC – National Research Council (WWW site: http:// www.nationalacademies.org/nrc). OGS – Istituto Nazionale di Oceanografia e Geofisica Sper- imentale (http://www.ogs.trieste.it). ORION-GEOSTAR-3 – Ocean Research by Integrated Ob- servation Networks (http://www.ingv.it/geo-star/ori- on.htm). PNRA – Programma Nazionale di Ricerche in Antartide (http://www.pnra.it). ROV – Remote Operated Vehicle (http://my.fit.edu/ ~swood/rov_pg2.html). R/V – Research Vessel. SN-1 – Submarine Network-1 (WWW site: http://www.in- gv.it/geostar/ sn.htm). TFH – Techniche FachHochschule (WWW site: http:// www.tfh-berlin.de). TUB – Technische Universität Berlin (WWW site: http:// www.tu-berlin.de). VHF – Very High Frequency. REFERENCES BERANZOLI, L., A. DE SANTIS, G. ETIOPE, P. FAVALI, F. FRUGONI, G. SMRIGLIO, F. GASPARONI and A. MARIGO (1998): GEOSTAR: a GEophysical and Oceanograph- ic STation for Abyssal Research, Phys. Earth Planet. Int., 108, 175-183. BERANZOLI, L., T. BRAUN, M. CALCARA, D. CALORE, R. CAMPACI, J.-M. COUDEVILLE, A. DE SANTIS, G. ETIOPE, P. FAVALI, F. FRUGONI, J.-L. FUDA, F. GAMBERI, F. GAS- PARONI, H.W. GERBER, M.P. MARANI, J. MARVALDI, C. MILLOT, P. PALANGIO, G. ROMEO and G. SMRIGLIO (2000a): European seafloor observatory offers new possibilities for deep-sea study, Eos, Trans. Am. Geo- phys. Un., 81, 45-49. BERANZOLI, L., T. BRAUN, M. CALCARA, A. DE SANTIS, D. DI MAURO, G. ETIOPE, P. FAVALI, F. FRUGONI, C. MON- 679 A fleet of multiparameter observatories for geophysical and environmental monitoring at seafloor TUORI, P. PALANGIO, G. ROMEO, G. SMRIGLIO, F. GAM- BERI, M.P. MARANI, J.-L. FUDA and C. MILLOT (2000b): GEOSTAR, an observatory for deep-sea geophysical and oceanographic researches: characteristics, first sci- entific mission and future activity, Mem. Soc. Geol. It., 55, 491-497. BERANZOLI, L., P. FAVALI and G. SMRIGLIO (Editors) (2002): Science-technology synergy for research in marine en- vironment: challenges for the XXI century, Develop- ments in Marine Technology Series (Elsevier, Amster- dam), 12, pp. 268. BERANZOLI, L., T. BRAUN, M. CALCARA, P. CASALE, A. DE SANTIS, G. D’ANNA, D. DI MAURO, G. ETIOPE, P. FAVALI, J.-L. FUDA, F. FRUGONI, F. GAMBERI, M.P. MARANI, C. MILLOT, C. MONTUORI and G. SMRIGLIO (2003): Mission results from the first GEOSTAR Observatory (Adriatic Sea, 1998), Earth Planets Space, 55, 361-373. BERANZOLI, L., D. CALORE, P. FAVALI, J. MARVALDI and M. NICOT (2004): ORION-GEOSTAR-3: a prototype of seafloor network of observatories for geophysical, oceanographic and environmental monitoring, in Pro- ceedings 14th International Off-shore and Polar Engi- neering Conference (Toulon, France), vol. II, 371-376. BERTA, M., F. GASPARONI and M. CAPOBIANCO (1995): Abyssal Benthic Laboratory (ABEL): a novel approach for long-term investigation at abyssal depths, J. Mar. Syst., 6, 211-225. BLANDIN, J., R. PERSON, J.M. STROUT, P. BRIOLE, G. ETIOPE, M. MASSON, S. SMOLDERS, V. LYKOUSIS, G. FERENTINOS and J. LEGRAND (2003): ASSEM: a new concept of re- gional observatory, in Proceedings 3rd International Workshop on Scientific Use of Submarine Cables and Re- lated Technologies, Tokyo, Japan, edited by J. KASAHARA and A.D. CHAVE, IEEE Catalogue No. 03EX660, 240-243. CALCARA, M., L. BERANZOLI, T. BRAUN, D. CALORE, A. DE SANTIS, G. ETIOPE, P. FAVALI, F. FRUGONI, F. GASPA- RONI, C. MONTUORI and G. SMRIGLIO (2001): MABEL: a multidisciplinary benthic laboratory for deep-sea, long-term monitoring in the Antarctic, Terra Antarcti- ca, 8, 115-118. CENEDESE, S., M. CALCARA, G. D’ANNA, K.-U. EVERS, P. FAVALI and F. GASPARONI (2004): MABEL: The first seafloor observatory for multidisciplinary long-term monitoring in polar environment, in Proceedings 14th International Off-shore and Polar Engineering Confer- ence, Toulon, France, vol. I, 787-794. CHAVE, A.D., R. BUTLER and T.E. PYLE (Editors) (1990): Proceedings 1st International Workshop on Scientific Uses of Undersea Cables, Honolulu, Hawaii (JOI, Washington DC), pp. 310. CLAUSS, G. and S. HOOG (2002): Deep-sea challenges of marine technology and oceanographic engineering, in Science-Technology Synergy for Research in the Ma- rine Environment: Challenges for the XXI Century, ed- ited by L. BERANZOLI, P. FAVALI and G. SMRIGLIO, De- velopments in Marine Technology Series (Elsevier, Amsterdam), 12, 133-142. CLAUSS, G., S. HOOG, F. STEMPINSKI and H.W. GERBER (2004): Advanced deepwater intervention with MODUS – Latest results from model tests and full-scale opera- tions, in Proceedings 14th International Off-shore and Polar Engineering Conference, Toulon, France, vol. II, 377-386. DE SANTIS, A., D. DI MAURO, L. CAFARELLA, R. D’ANNA, L. GAYA-PIQUE, P. PALANGIO, G. ROMEO and R. TOZZI (2006): Deep seafloor magnetic observations under GEOSTAR project, Ann. Geophysics, 49 (2/3), 681- 693 (this volume). ETIOPE, G., P. FAVALI, J.-L. FUDA, F. ITALIANO, M. LAUBEN- STEIN, C. MILLOT and W. PLASTINO (2006): The Benth- ic Boundary Layer: geochemical and oceanographic data from the GEOSTAR-2 Observatory, Ann. Geo- physics, 49 (2/3), 705-713 (this volume). FAVALI, P. and L. BERANZOLI (2006): Seafloor observatory science: a review, Ann. Geophysics, 49 (2/3), 515-567 (this volume). FAVALI, P., G. SMRIGLIO, L. BERANZOLI, T. BRAUN, M. CAL- CARA, G. D’ANNA, A. DE SANTIS, D. DI MAURO, G. ETIOPE, F. FRUGONI, V. IAFOLLA, S. MONNA, C. MON- TUORI, S. NOZZOLI, P. PALANGIO and G. ROMEO (2002): Towards a permanent deep-sea observatory: the GEO- STAR European experiment, in Science-Technology Synergy for Research in the Marine Environment: Chal- lenges for the XXI Century, edited by L. BERANZOLI, P. FAVALI and G. SMRIGLIO, Developments in Marine Tech- nology Series (Elsevier, Amsterdam), 12, 111-120. FAVALI, P., SN-1 TEAM and NEMO COLLABORATION (2003): SN-1: the first node of the Italian seafloor observatory network – Background and perspective, in Proceedings 3rd International Workshop on Scientific use of Subma- rine Cables and Related Technologies, Tokyo, Japan, edited by J. KASAHARA and A.D. CHAVE, IEEE Catalogue No. 03EX660, 19-24. FAVALI, P., L. BERANZOLI, M. CALCARA, G. D’ANNA, G. ETIOPE, F. FRUGONI, N. LO BUE, G. MARINARO, S. MON- NA, C. MONTUORI, T SGROI, F. GASPARONI, S. CENE- DESE, F. FURLAN, G. FERENTINOS, G. PAPATHEODOROU, D. CHRISTODOLOU, J. BLANDIN, J. MARVALDI, J.-F. ROLIN, G. CLAUSS, H.W. GERBER, J.-M. COUDEVILLE, M. NICOT, E.R. FLUEH, F. GAMBERI, M.P. MARANI and G. NERI (2004a): Single-frame multiparameter plat- forms for seafloor geophysical and environmental ob- servations: projects and missions from GEOSTAR to ORION, in Proceedings OCEANS’04, Kobe, Japan, 2000-2007. FAVALI, P., L. BERANZOLI and A. MARAMAI (2004b): Review of the Tyrrhenian Sea seismicity: how much is still to be unknown?, in From Seafloor to Deep Mantle: Archi- tecture of the Tyrrhenian Back-arc Basin, edited by M.P. MARANI, F. GAMBERI and E. BONATTI, Mem. De- scr. C. Geol. Ital., LXIV, 57-70. GASPARONI, F., D. CALORE and R. CAMPACI (2002): From ABEL to GEOSTAR: development of the first European deep-sea scientific observatory, in Science-Technology Synergy for Research in the Marine Environment: Chal- lenges for the XXI Century, edited by L. BERANZOLI, P. FAVALI and G. SMRIGLIO, Developments in Marine Tech- nology Series (Elsevier, Amsterdam), 12, 143-159. GERBER, H.W. and G. CLAUSS (2005): Space shuttle MODUS – Key system for the installation of networks of Benthic stations, in Proceedings OMAE05. 24th In- ternational Conference on Off-shore Mechanics and Arctic Engineering, Halkidiki, Greece. IAFOLLA, V. and S. NOZZOLI (2002): Gravimeter for deep- sea measurements, in Science-Technology Synergy for Research in the Marine Environment: Challenges for 680 Paolo Favali et al. the XXI Century, edited by L. BERANZOLI, P. FAVALI and G. SMRIGLIO, Developments in Marine Technology Se- ries (Elsevier, Amsterdam), 12, 183-197. IAFOLLA, V., S. NOZZOLI, E. FIORENZA and V. MILYUKOV (2006): Deep-sea gravity measurements: GEOSTAR-2 mission results, Ann. Geophysics, 49 (2/3), 695-704 (this volume). JOURDAIN, J.Y. (1999): First trial of GEOSTAR, the geo- physical and oceanographic European station for abyssal research, EC Project Information Booklet EUR18885, edited by G. OLLIER, pp. 31. KASAHARA, J. and A.D. CHAVE (Co-chairs) (2003): Proceed- ings 3rd International Workshop on Scientific Use of Sub- marine Cables and Related Technologies, Tokyo, Japan, edited by J. KASAHARA and A.D. CHAVE, IEEE Catalogue No. 03EX660, pp. 315. MARANI, M.P., F. GAMBERI and E. BONATTI (Editors) (2004): From seafloor to deep mantle: architecture of the Tyrrhenian back-arc basin, Mem. Descr. C. Geol. d’It., LXIV, pp. 195. MARINARO, G., G. ETIOPE, F. GASPARONI, D. CALORE, S. CENEDESE, F. FURLAN, M. MASSON, P. FAVALI and J. BLANDIN (2004): GMM-a gas monitoring module for long-term detection of methane leakage from the seafloor, in GEM-Geologic Emissions of Methane from Lands and Seafloor: Mud Volcanoes and Observing Sys- tems, edited by G. ETIOPE and P. FAVALI, Environ. Geol., 46 (8), 1053-1058, doi: 10.1007/s00254-004-1092-2. MARVALDI, J., Y. AOUSTIN, G. AYELA, D. BARBOT, J. BLANDIN, J.-M. COUDEVILLE, D. FELLMANN, G. LOAËC CH. PODEUR and A. PRIOU (2002): Design and realisa- tion of communication systems for the GEOSTAR project, in Science-Technology Synergy for Research in the Marine Environment: Challenges for the XXI Cen- tury, edited by L. BERANZOLI, P. FAVALI and G. SM- RIGLIO, Developments in Marine Technology Series (El- sevier, Amsterdam), 12, 161-181. MONNA, S., F. FRUGONI, C. MONTUORI, L. BERANZOLI and P. FAVALI (2005): High quality seismological recordings from the SN-1 deep seafloor observatory in the Mt. Etna region, Geophys. Res. Lett., 32, L07303 doi:10.1029/ 2004GL021975. MONTAGNER, J.-P. and Y. LANCELOT (Editors) (1995): Pro- ceedings International Workshop Multidisciplinary Ob- servatories on the Deep Seafloor (INSU/CNRS, IFRE- MER, OSN/USSAC, ODP-France and ODP-Japan, Mar- seille, France), pp. 229. NRC (NATIONAL RESEARCH COUNCIL) (2000): Illuminating the Hidden Planet. The future of Seafloor Observatory Science (National Academy Press, Washington DC), pp. 135. PETERSON, J.R. (1993): Observations and modelling of seis- mic background noise, US Geol. Surv. Open File Rep. 93-322, pp. 94. PRIEDE, I.G., M. SOLAN, J. MIENERT, R. PERSON, T.C.E. VAN WEERING, O. PFANNKUCHE, N. O’NEILL, A. TSELEPIDES, L. THOMSEN, P. FAVALI, F. GASPARONI, N. ZITELLINI, C. MILLOT, H.W. GERBER, J.M.A. DE MIRANDA and M. KLAGES (2003): ESONET – European Seafloor Obser- vatory NETwork, in Proceedings 3rd International Workshop on Scientific Use of Submarine Cables and Related Technologies, Tokyo, Japan, edited by J. KASA- HARA and A.D. CHAVE, IEEE Catalogue No. 03EX660, 263-265. PRIEDE, I.G., P. FAVALI, M. SOLAN, F. GASPARONI, J. MIENERT, N. ZITELLINI, R. PERSON, C. MILLOT, T.C.E. VAN WEERING, H.W. GERBER, O. PFANNKUCHE, J.M.A. DE MIRANDA, N. O’NEILL, M. KLAGES, A. TSELEPIDES, P. SIGRAY and L. THOMSEN (2004): ESONET – Euro- pean Seafloor Observatory NETwork, in Proceedings OCEANS’04 MTS/IEEE TECHNO-OCEAN’04, Kobe, Japan, IEEE Catalogue No. 04CH37600C, 2155-2163. RIGAUD, V., D. SEMAC, M. NOKIN, DESIBEL TEAM, G. TI- ETZE, H. AMANN, V. GOETZ and A. PASCOAL (1998): New methods for DEep-Sea Intervention on future BEnthic Laboratories, DESIBEL project – Final re- sults, comparison of concepts and at sea validation, in Proceedings of the IEEE Conference OCEANS ’98, Nice, France (on CD-ROM). ROMANOWICZ, B., K. SUYEHIRO and H. KAWAKATSU (Edi- tors) (2001): OHP/ION joint symposium long-term ob- servations in the oceans. Current status and perspec- tives for the future, Workshop Rep., Yamanashi Pref., Japan, pp. 188. UTADA, H., K. NOGUCHI, C. HARAYAMA and N. NATSUSHIMA (Editors) (1997): Proceedings International Workshop on Scientific Use of Submarine Cables, Okinawa, Japan, pp. 234. THIEL, H., K.O. KIRSTEIN, C. LUTH, U. LUTH, G. LUTHER, L.A. MEYER-REIL, O. PFANNKUCHE and M. WEYDERT (1994): Scientific requirements for an abyssal benthic laboratory, J. Mar. Sys., 4, 421-439. WEBB, S.C. (1998): Broad-band seismology and noise un- der the ocean, Rev. Geophys., 36 (1), 105-142.