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Science Mission Task 4.2 Tsunami Detection   

Integrating sea bottom (high accuracy pressure for tsunami detection) and water column monitoring platforms.

In the framework of the EuroSITES project the POSEIDON-Pylos observatory of the SE Ionian has been upgraded with the addition of an autonomous seabed platform. This is EuroSITES Milestone 2.


Figure 1: Schematic presentation the POSEIDON-Pylos
observatory hosting the autonomous seabed platform.
Figure 2: Deployment of the seabed platform at
the POSEIDON-Pylos site in November 2008

The deployment of the deep sea platform at the POSEIDON-Pylos site under task 4.2 was originally planned for month 6 (Milestone #2, September 08). This was achieved with a small (2 month) delay in November 2008 (Month 8) due to delays in the delivery of equipment (including a customs strike in Greece delaying the delivery of the platform before the scheduled POSEIDON cruise in September 08).

The platform was deployed in November 2008 (M8) and has enriched with close-to-seabed measurements the observing capabilities of the POSEIDON-Pylos site that continues its standard water column (0-1000m) and air-sea interaction observations. The communication between the seabed platform a nd the surface buoy is carried out through acoustic modems and allows near real time transmission of the data. The platform is equipped with a high accuracy pressure sensor and the necessary software for real time signal analysis for possible Tsunami detection, as well as an SBE-16 for temperature and salinity measurements. During the pilot operation that followed the deployment of the platform, two problems have been identified: erroneous pressure data leading to false Tsunami alarms (figure 3) and events of unsuccessful communication between the platform and the surface buoy (figure 4). The platform was recovered in March 2009 in order to continue laboratory tests and resolve these problems as well as to carry other minor software upgrades (new bios etc).

Following communication with the pressure senor manufacturer, the erroneous data have been attributed to gas bubbles trapped into the instrument (in the tubing between the pressure port in the lid to the pressure transducer). The system has been sent to the platform manufacturer for further lab and in-situ tests. The communication problems between the platform and the buoy are attributed to shadowing effects of seabed anomalies. A more appropriate area with smaller topographic anomalies will be selected during the next deployment of the seabed platform in early December 2009.

Figure 3:Time series of high resolution (15 sec) pressure data from the seabed platform. The spikes between 14th and 17th of January 2009 indicate malfunction of the pressure sensor. According to the manufactures it is attributed to trapped air bubbles.

Figure 4:Time series of pressure data from the seabed platform. Step-like variability indicates communication problems between the platform and the surface buoy.

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The SE Ionian Sea is characterised by:

  • Unique geological processes including active faulting, salt tectonics and active subduction (shear strain) responsible of upward migration of deep fluids and generation of an extensive mud volcano belt and brine lakes;
  • High seismicity that is also related to tele-tsunami generation (i.e. 365AD mega event following an approximately 8.5R earthquake shock).

This area will become "The greater Poseidon-Pylos site" in the SE Ionian Sea equipped with the latest submarine cable technology and recently announced massive investment by national funding authorities of 50M Euro within the frame of ESFRI initiatives (KM3Net-PP, EMSO-PP). The area has been selected due to its unique environment and the infrastructure will be used for a wide variety of multidisciplinary observations both in WP3 and 4. In this area an autonomous bottom platform equipped with a high accuracy pressure sensor will be deployed at a depth of 2000m, in the framework of the Greek national-funded POSEIDON-II project, in order to provide advanced warning of tsunami.

The aim of this task is to integrated the bottom pressure observations with the hydrological water column and near-bottom measurements (developed under WP3) in order to demonstrate the value of combining different co-located platforms and sensors into a distributed system with unified operational procedures.


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EuroSITES is a FP7 Collaborative Project coordinated by the
National Oceanography Centre, Southampton, UK

Call FP7-ENV-2007-1, grant agreement N 202955
Sub-Activity 6.4.1. Earth Observation; Monitoring the ocean interior, seafloor, and subseafloor

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