The Ocean-DAS project has developed novel Distributed Acoustic Sensing (DAS) systems based on chirped-pulse technology with unmatched low-frequency performance (at least 20 dB better than other available DAS systems in the market in strain noise PSD at mHz frequencies). These novel DAS systems have enabled observing submarine seismic processes with a level of detail and spatial coverage that is not available so far, neither with conventional DAS technology, nor with available Ocean-Bottom Seismometer systems. With this technology we have demonstrated the measurement of (i) ocean surface gravity waves (including their dispersion curves with an extremely high level of accuracy), (ii) the spatial dependence of sea currents over tens of km, (iii) the dynamics of infragravity waves and tidal waves in a large coastal area and (iv) hydroacoustic T-waves derived from teleseismic events in a fiber-optic sensing array (for the first time to our knowledge). A market analysis has also revealed that this technology has an extremely high potential for becoming a new market tool in the early warning of tsunamis, where currently there is no good solution (DART buoys and OBS arrays are expensive or unreliable and call for a new solution with low deployment costs such as the one presented here). The market potential of Ocean-DAS technology in the tsunami early warning market is clear. Ocean-DAS technology can clearly detect tsunamigenic events (offshore earthquakes) and can also confirm water column elevation changes along the optical fibre path. Also, it has the potential of being much cheaper and more reliable than current options (OBS systems and DART buoys). As such, it is the intention of the project members to develop this technology into a specific product for tsunami warning. The market opportunity is very clear. In addition, the technology developed in Ocean-DAS has been proved to be effective for other potential applications, including the distributed measurement of electric fields and the distributed measurement of solar irradiance. While these works are very preliminary, they illustrate other possible applications of interest for the technology.
The technology has been successfully licensed to two European companies in the domain (Aragon Photonics, ES, and Omnisens, CH), which are already selling systems in to specific labs in Geophysics and Seismology. Additional work will be needed to transform Ocean-DAS technology into a product for tsunami early warning. This innovative system, based on DAS data, will issue more timely alerts when a tsunamigenic earthquake is first detected by the submarine fiber array, which is of great relevance in regions where tsunami warning systems do not exist, and will increase the “golden time” of already operative warning systems. Due to the uncertainties associated with the predicted parameters that characterize the incoming tsunami, it is possible that a wrong decision may be made (missed alarms or false positives). By also monitoring the tsunami water waves, this new DAS-based warning system will substantially increase the reliability of the alert. Also, it is expected that the seafloor monitoring capacity of the developed DAS system will be widely used in gaining understanding and scientific knowledge on important environmental processes affecting the world, like climate change and coastal erosion.
