Field: Damage-reducing technique, Natural disaster management
Global Technical function: Geomatic monitoring, Sensing
Technical Function Unit: Automatized and remote sensing, Data analysing, Identifying, Information and observation system, Networking

NEAREST

Since the devastating Asian tsunami in the Indian Ocean in 2004, the interest in systematic studies of the Mediterranean tsunami situation and related damage-reducing techniques has been growing.  Tsunamis in the Mediterranean Sea are not as frequent as those in the Pacific or Indian Oceans, but have nevertheless historically caused severe damage and loss of lives. In the NEAREST project (Integrated observations from NEAR shore sourcES of Tsunamis: towards an early warning system), the complex situation of near-shore tsunamis has been thoroughly analysed by experts from ten scientific institutions and one company. The project was funded by the European Union Sixth Framework Programme (FP6), a grant funding programme, and coordinated by the Institute of Marine Sciences in Italy.

A tsunami warning system not only has to be quick, it must also be accurate. To achieve this, the project developed a prototype for tsunami warning called TEWS(Tsunami Early Warning System). The technology of this information and observation system prototype was based on improvements of a tsunami detector from other EC projects, including
automatised and remote sensing devices and software for tsunami detection.  The detector gathers data from the sea bottom through a pressure sensor, a triaxial broad band seismometer and a triaxial accelerometer. The prototype was installed on the deep-sea underwater observatory GEOSTAR during one year, situated outside the south-west coast of Portugal at a depth of more than 3.200 meters and strategically placed above a large geological structure identified as a source for tsunami activity.

The prototype is specific for geomatic monitoring of tectonian structures placed very close to the coast and is taking dynamical and kinematical effects due to sea floor motion into account when performing tsunami signal measurements and identification. The systems’
data analysing tsunami detection algorithm can perform a real-time recognition of tsunami waves as small as a centimetre, using bottom pressure data. 

Data from the underwater sensing system in the prototype was communicated to a surface buoy, but the complexity of deep-sea communication restricted the interaction between these components. The conditions this far below sea level are making light signalling impossible, and radio waves do not travel well through water.  Therefore, resembling the acoustic communication of whales, the means of communication from the underwater device to the surface was based on transmissions via a dual acoustic link. The buoy was in turn communicating with land-based stations via satellite. The communication chain from deep-sea to land was essentially carrying two types of information; periodic data sent every 6 hours to ensure that all devices are functioning properly, and near-real-time messages in case of a pressure or seismic event.

The crucial testing of the prototype system had to be performed through feasibility studies in simulators, since tsunami events are not frequently striking the Mediterranean region. Creating realistic data flows for scenario analysis and evaluating the consequences, the two simulators that were developed within the project could also be of further use by authorities in preparation for crisis.

At the end of the project, the system prototype was implemented in the Instituto de Meterologia in Lisbon to release an alert in case of tsunamigenic seismic events. The technology readiness level is therefore estimated to be an 8 on the TRL scale.

The results from the project were not only exceeding the expectations in terms of quality, they were also vast in quantity. Apart from the development of the natural disaster management prototype, the project team was successful in identifying and characterising potential large tsunami sources in the Gulf of Cadiz and in Southwest Portugal. They could also establish evidence of prehistorically occurring tsunamis and earthquakes from sediments in the Mediterranean area, and undertook an exhaustive investigation of tsunami generation mechanisms resulting in a fine-tuning of the existing tsunami generation models.  Additionally, the project brought the three seismic centers in Portugal, Spain and Morocco into a networking collaboration that would be able to locate and estimate the true size of seismic events in the Southwest Iberian region within five minutes and could potentially be responsible for issuing tsunami alerts on national level.