EC-NEAREST project: First Tsunami Underwater Observatory in the Gulf of Cadiz

On August 25 at 10:15 p.m. G.M.T. the first prototype of an underwater tsunami observatory was successfully deployed at 3207 m water depth in the Gulf of Cadiz. The deployment,150 km South of Portugal, was planned within the NEAREST project (Integrated observations from NEAR shore sources of Tsunamis: towards an early warning system - EC, cont. 37110) The observatory is based on the GEOSTAR platform, previously developed by a consortium led by INGV. The ocean bottom equipment includes a broad-band seismometer, hydrophone, gravitymeter and pressure gauge, allowing for cross-checking of the signals. Pre-processing of seismic and pressure data is done underwater. A relay surface buoy, equipped with additional meteorological sensors, is in acoustic link with the seafloor platform and performs satellite real-time transmission to the shore stations, where the integration of the marine with land data from operating networks will improve the reliability of the tsunami detection strategy. Additional sensors can be installed, in a framework of a multi-parameter seafloor observatory, able to characterise earthquake/ tsunami processes and to extend its capacity to a larger set of monitoring strategies. The deployment, performed by the R/V Urania, was supervised by a team of scientists and engineers from the partners in the project. The site of the seafloor observatory was selected according to the available geological and bathymetric data, to maximise proximity to the potential sources; its present position is 36º 21.875'N;09º28.885'W; 3207 m w.d. Data are currently being acquired and processed on an experimental basis and integrated with information from land monitoring networks of: Portugal, Spain and Morocco.This observatory is an important milestone towards a European tsunami warning system - UNESCO IOC resolution of December 2005 to develop the "North East Atlantic and Mediterranean Tsunami Warning System".