Beranzoli, Laura

Guardato, S.

Iannaccone, G.

Vasallo, M.

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INSTRUMENTATION VIEWPOINTSessions312. Planar Optode: A so called planar optode has been used to obtain the oxygenconcentration in two dimensions in the sediment and at the sediment-water interface. A planar optode is like an “inverted periscope” which is gently inserted into the sediment. Through a spe-cial optical technique, called luminescence quenching, it ispossible to obtain high resolution oxygen images. From the oxygen images oxygen concentration gradients (profi les) can be extracted. About 600 oxygen profi les can be extracted from each image and from the profi les the sediment oxygen consumption can be calculat-ed, which gives an independent estimate of carbon turnover rates.3. Oxygen gradients in the water: Oxygen optodes have been mount-ed at diff erent levelsin the water column. These sensors reveal the dynamism of the aquatic environmentand it is possible to extract gradients with lower concentrations for example closer tothe bottom and higher close to layers with active primary produc-tion. Together with information about the currents we have devel-oped methods that can be used calculate the oxygen consumption/production in diff erent layers.CUMASCABLED UNDERWATER MODULE FOR ACQUISITION OF SEISMOLOGICAL DARA FOR GEO-HAZARD MONITORING IN SHALLOW WATERG. Iannaccone (1), S. Guardato (1), M. Vassallo (2), L. Beranzoli (1)(1) Istituto Nazionale di Geofisica e Vulcanologia,Via Diocleziano 328, 80124 Naples, ITALY+39-081-6108305, iannaccone@ov.ingv.it(2)  Dipartimento di Scienze Fisiche, Università degli Studi di Napoli “Federico II” 1. IntroductionCUMAS is an underwater module developed for the acquisition of geophysical signals in shallow seafl oor for geohazard monitoring in volcanic areas. It was conceived for a specifi c application in the Campi Flegrei Caldera (Southern Italy) where the main features of the present volcanic activity consists of slow soil movements (brady-seism) accompanied by intense and shallow seismic activity. The latest strong episode occurred in the period 1982-84 with a ground uplift of more than 170 cm followed by a slow and continuous sub-sidence still ongoing with of small amplitude uplift episodes (few centimeters). It is worth noting that the seismic activity only appears during the uplift phase.CUMAS is the fi rst step toward the extension of the present operating land-based monitoring networks of the Campi Flegrei in the marine sector of the Caldera, roughly covering more than one third of the volcanic area. 2. CUMAS features and functionalities CUMAS has the aim to    -continuously acquire on the seafl oor geophysical and oceano        graphic data according to a single time reference;    -transmit acquired data in real time to a acquisition centre on land;    -receive commands from the land centre and accordingly modify its acquisition confi guration.CUMAS is powered through a cable connecting the module to a sur-face infrastructure; this ensure a long lasting deployment on the sea-fl oor.All these features make CUMAS fully integrated in centralised moni-toring system of the Neapolitan volcanic areas (Vesuvio, Campi Fle-grei and Ischia Island) managed by Osservatorio Vesuviano-INGV.CUMAS consists of a frame of steel with a shape of truncated pyramid of about 1 m high and a square base of 1 m per side. The total weight including the equipment is about 430 kg in air.In the CUMAS frame the following sensor packages are installed:1. seismological sensors aimed at recording local earthquakes related to volcanic activity and artifi cial explosions often caused by fi sher-men; the sensors include   -a three component broad band seismometer (0.025 s - 40 s) Guralp CMG-40T OBS with auto-levelling platform    - a broad band hydrophone (1 Hz – 65kHz) Sensor Technology SQ03 model2. physical oceanographic sensors are aimed at the long-term moni-toring of the water current regime also useful for seafl oor seismic microtremor studies; a further task consists in testing the feasibil-ity of the use of water pressure measurements at seafl oor to detect changes in water column pressure potentially related to bradiseismic activity. The oceanographic sensors include   -a single point three component acoustic current meter 3D-ACM Falmouth   -a pressure gauge Series 8000 Paroscientifi c.Data acquisition in performed by a Quanterra Q330 digitiser equipped with external hard disk as local mass storage. The digitiser is installed inside a cylindrical aluminium vessel and it is used to acquire the seis-mological sensors, both sampled at 125 sps. The data acquistion analog sensors and data acquisition embedded computer for sensors with digital output. The physical-oceanograph-ic sensors with digital output are acquired by an  embedded compu-ter with Linux o.s.Further sensors installed in the vessel are acquired by the Linux PC, namely tilt and heading sensors, for the measure of the real module attitude on the seafl oor, and status sensors for the monitoring of the internal status of the vessel (e.g., internal temperature, power absorp-tion, water intrusion).Both acquisition systems are linked via Ethernet cable to a router con-nected to an electro-mechanical cable for the real time data trans-mission to the sea surface. A Wi-Fi communication system ensures the seafl oor data transfer to the land acquisition centre in the city of Naples.M2INSTRUMENTATION VIEWPOINTSessions32Figure 1. CUMAS fully equipped in lab during tests; the acquisi-tion system and the seismic sensor were temporary kept out of the frame to check the operation.3. Deployment and operationCUMAS has been developed to be installed in the sea sector of the Campi Flegrei Caldera at 97 m w.d., from 2 to 3 km far from shore and about 4 km far from the acquisition land centre.A buoy (elastic beacon), previously deployed and presently operat-ing, is used as the support infrastructure for CUMAS. The buoy, 8 m high above the sea level, is equipped with batteries charged by solar panels and aeolic generator. A CISCO bridge, equipped with omnidi-rectional antenna, allows the data transmission to land.A meteo station is also mounted on the buoy providing the local meteo measurements (e.g., barometric pressure, wind velocity and direction, rain-meter, thermometer) to allow correlation of the air and seafl oor data.The deployment of CUMAS is performed by lowering the module in the sea water by means of its own electro-mechanical cable with the support of a ship equipped with a crane. Once the module is on the seafl oor, the cable is deployed on the seafl oor too and its end is con-nected to a junction box installed on the top of the buoy.The CUMAS operation on the seafl oor is planned to be at least 1 year long.Figure 2. The Gulf of Pozzuoli (west of Naples) and the site (yellow triangle) selected for the deployment of CUMAS. 4. Expected resultsCUMAS represents the fi rst marine node of a land-sea integrated net-work for geo-hazard monitoring. Its data, continuously sent to the land acquisition center, will be integrated with those belonging to the whole surveillance system. In particular the seismological data will be used jointly with the land seismic network and contribute to improve the location of the earthquakes occurring in the sea sec-tor of the Caldera. Furthermore, as demonstrated by Vassallo et al. [1] this use will enhance the seismic detection capability of low en-ergy earthquakes usually masked by the high level anthropic seismic noise typical of densely populated areas.The pressure gauge measurements, corrected for tidal eff ect and complemented with coastal tide gauge network data, can for the fi rst time estimate vertical seafl oor bradiseismic movement, till now measured only on land. 5. References [1] Vassallo M., Bobbio A. and Iannaccone G., Analysis of broad band seismic data acquired under the sea of Pozzuoli Gulf (Southern Italy), European Geophysical Union General Assembly, Wien, 2006.REAL TIME TRANSMISSOIN OF CURRENT AND TURBIDITY DATA FROM THE NEAR BOTTOM VAR CANYON SYSTEMJ. Blandin, A. Vangriesheim, J. Legrand, J.Y. Coail, B. LeildéIfremer, Centre de Brest – BP70 – 29280 Plouzané+33 298 224 688  -  Jerome.Blandin@ifremer.fr1. IntroductionUnder the umbrella of the EU-FP6 HERMES program, Ifremer is com-mitted in the monitoring of the particle dynamics in the Var canyon. For this purpose, several seabed measurement stations with a near-real time link to shore were installed, enabling the monitoring of the Var Valley from Brest. Two currentmeters and one fl uorometry and turbidity sensor, installed on the levee of the valley at a depth of 2000 metres, send their measurement data every six hours to shore. The paper describes the measurement and data transmission system, its functioning and the main lessons learnt along two years of imple-mentation.2. System description, Results and Discussion Among the various measurement stations and moorings installed in the Var Canyon [1] two stations were fi tted with the SEAMON technol-ogy developed during the EU-FP5 ASSEM project [2]. This technology enables the measurement data from various local deep sea sensors to be collected as and when generated, then periodically forwarded to a data base on shore. MAP3 (currentmeter, fl uorometer and turbid-ity sensor near the seabed) and SSB (currentmeter) stations benefi ted from this service. The near real-time link comprises one acoustic seg-ment between each seafl oor station and a relay-buoy, followed by an Iridium satellite segment joining the buoy to a shore server. The link is bi-directional, allowing the modifi cation of the measurement parameters at any time, by an operator on shore.M2

CUMAS cabled underwater module for acquisition of seismological dara for geo-hazard monitoring in shallow water

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