Ocean Bottom Observatory in Marmara Sea

March 08

As an industry first Guralp Systems Ltd. was recently awarded the contract for the design, integration, and installation of a complete, multidisciplinary scientific ocean bottom observatory (OBO). The turnkey system will be installed in the Marmara Sea, Turkey, to augment the existing landbased networks for monitoring the seismicity along the North Anatolian Fault. The contract comprises not only of the delivery of the sensors, digitizers and data transmission modules but also of the laying of the optical cables and nodes for subsea data telemetry and building a land station to receive and distribute the data.

The North Anatolian Fault (NAF) is one of the most active and dangerous earthquakes faults in the world. Its seismicity is currently being monitored by a great number of land based stations, many of them equipped with our CMG-3T, CMG-40T and CMG-5T sensors. As a substantial part of the western section of the NAF runs through the Marmara Sea west of Istanbul a gap exists in the network coverage. To close this gap Turkish Telecom in a joint project with Kandilli Observatory of Bogazici University in Instanbul and Sentez Electronics Engineering Ltd. will install several integrated ocean bottom observatories (OBO) in the Marmara Sea with cabled links to a central land station. The deployment depth will vary between 400 and 1200 m water depth.

The OBO network will consist of 5 separate stations, each equipped with:

The analogue output of these sensors will be interfaced to our CMG-DM24 mkIII 24-bit digitisers. The back end of the digitiser is connected to a CMG-DCM data communications module which will transmit the data via optical cable to a landstation, which in turn is connected to the data acquisition system at Kandilli Observatory.

Guralp Systems Ltd. will not only supply the seismic sensors, digitizers and DCMs but will also integrate the other sensors into the OBO. In addition GSL will develop the interfaces to connect each OBO to the optical sea floor cable, lay the cable, connect the OBO and build the landstation for on-shore data acquisition and dissemination — in short, deliver the complete turn-key ocean bottom observatory network.

GSL has been building its own Ocean Bottom Seismometers for over 20 years, and has supplied more than a hundred sensors as the hearts of third party OBS.

This contract underscores the position of Guralp Systems Ltd. as the world leader in the development and distribution of ocean bottom equipment for seismic monitoring and seismological research.

Map of the deployment