GA collaborative innovation that uses telecom subsea infrastruc- tures to help scientists in their understanding of our planet.
White Paper The seabed is often seen as a place that is not subject to change. However, it is subject to constant change caused by a variety of factors. Some changes are caused by interac- Subsea telecoms cables: tions between the ocean and the seabed, while longer-term changes occur far below A driver for scientific research the surface, in the crust of our planet. Because more than 70% of the earth’s surface is covered by water, research is very difficult to perform. Traditionally, research in sub-sea regions has only been possible Chris Atherton - Senior Research Engagement Officer - GÉANT using large research vessels or sensors tethered by very expensive dedicated cable sys- Auke Pals - Project Manager - GÉANT tems usually limited to near-coastal installations. This limits the ability of the scientific community to investigate what is happening in our Oceans on a broad scale. Dr Mohammad Belal - National Oceanography Centre - GFZ Angello Strollo - Member of Executive Committee of ORFEUS. Head of GEOFON - service of the GFZ The EllaLink cable that is being deployed across the Atlantic, between Portugal and Frederik Tilmann - Member of Board of Directors of ORFEUS Brazil, has opened up an opportunity to integrate a scientific component into a com- mercial submarine cable system. GeoLab was created as a partnership between EllaLink, Introduction EMACOM, FCT, and GÉANT to provide an infrastructure for the benefit of the global scientific community. « Two thirds of the surface of our planet are covered by water and are still poorly instru- mented, which has prevented the earth science community from addressing numerous This infrastructure consists of a spare fibre pair built into the Funchal branch of the key scientific questions. The potential to leverage the existing fiber optic seafloor telecom EllaLink cable, which stretches out for 75km, southeast from the coast of Madeira, into cables that criss-cross the oceans, by using them as dense arrays of seismo-acoustic sen- the Atlantic Ocean. Along with the fibre, space, power, air-conditioning, storage, and sors, remains to be evaluated. Here, we report Distributed Acoustic Sensing measurements internet connectivity will be made available to researchers. Collectively, this testbed on a 41.5 km-long telecom cable that is deployed offshore Toulon, France. Our observa- service is called GeoLab. tions demonstrate the capability to monitor with unprecedented details the ocean-solid earth interactions from the coast to the abyssal plain, in addition to regional seismicity (e.g., a magnitude 1.9 micro-earthquake located 100 km away) with signal characteristics comparable to those of a coastal seismic station.”
Distributed sensing of earthquakes and ocean-solid Earth interactions on seafloor telecom cables, article published in Nature on 18th Dec. 2019. he ir t per a e t i ra tr t re e i ate Overview to remote sensing e e e i to a o - er ia S ea e e o S te As GeoLab is the first of its kind in the world, it is unclear exactly which types of research will ultimately be conducted using GeoLab. However, both abiotic and F A CE SPAI Marseille biotic research areas could be investigated: Madrid PO TUGAL Lisboa Barcelona 1. Seismology MADEI A Sines Funchal Seismology is a scientific discipline that deals with the analysis, description, and MO OCCO measurement of natural and artificial seismic waves. Studying these waves allows
Canary seismologists to image the interior structure of the Earth, inferring composition, Islands temperature and the distribution of fluids. Analysis of the seismic waves excited MAU ITA IA by earthquakes are used to infer its hypocentre (the latitude, longitude and depth Nouadhibou where the earthquake rupture begins), the orientation of the causative fault, the detailed distribution of the rupture. Done rapidly, this in formation can be used for tsunami early warning or to get a quick understanding of affected areas, or even CABO E DE Praia for detection of offshore earthquakes up to a few tens of seconds warning before strong shaking begins.
2. Continental plate movement F E CH GUIA A Kourou Plate tectonics describes a geological phenomenon in which parts of the Earth’s crust Fortaleza shift relative to each other. At one time, all the continents were united in one large supercontinent, Pangea. This shifting does not happen overnight; plate sliding occurs at a rate of several centimetres per year. The shifting causes changes and stresses B A IL in the earth’s crust that could trigger an earthquake. While these earthquakes are usually small and not noticeable, it is not uncommon for an earthquake of enormous magnitude to occur. Rio São Paulo Tectonic plates consist of continental crust, oceanic crust, or a combination of both. If undersea plates slide away from each other, a new oceanic crust is formed. If plates slide against each other, mountains can form. Also, an oceanic plate can dip under another plate. This phenomenon is called subduction, and generally gives rise to both volcanoes and giant earthquakes, which can trigger hugely destructive tsunamis (e.g. 2011 Japan, and 2004 Sumatra, where the tsunamis caused fatalities as far away as India and even East Africa).
3. Ocean Seabed interaction
The range of interactions with the seabed is diverse, with vertical and horizontal interactions with the seabed occurring. For example, a vertical motion of the seafloor as caused by an earthquake. Such an interaction can be very easy to observe with the • Seismology, volcanology, marine ecology and oceanic conditions are key to understanding right equipment given the associated impact on the surrounding areas. Horizontal the future of our planet. ocean-seabed interactions, however, are very difficult to observe without extensive local research at the relevant seabed location. • EllaLink Geolab initiative aims to provide the scientific community with real-time, accurmate and relevant data on seabed conditions along the EllaLink Cable route. Changes in the seabed can be due to a variety of causes, namely sea currents, sea creatures, and marine traffic. Some changes in the seabed are too smallt o be • EllaLink is the first telecoms submarine cable to integrate SMART cable concept. observed with other research methods. Technologies which utilise in-line strain- sensing, such as Distributed Acoustic Sensing (DAS), offer the opportunity to observe even the smallest changes in the seabed. Figure 1. Map of the EllaLink cable pointing out the location of GeoLab. Thus, it is possible to record the vibrations excited by the interaction of ocean currents and the seabed. By extracting the amplitude and frequency, it might be possible to understand the erosion of the seabed induced as a function of prevailing currents.
The seabed changes partly due to ocean currents, which also change the relief of the seabed and the ra tr t re eg ator rea i e body vegetation present on the seabed. The relief created by the ocean currents can have different influences operation on the seabed or the vegetation in the oceans. As the effects of this have only been studied to a limited extent, GeoLab can contribute to the science of the underwater world and other effects of sea currents.
Importantly, by continuously recording the ambient noise excited by these processes we could be able to map minute changes (sub percent) in the elastic properties of the seabed, a technique that is well established on land. On land, the susceptibility to velocity changes appears to be a good indicator for Ecosystem soil stability and is strongly correlated with the occurrence of landslides. It seems reasonable that this observation carries over into the marine realm, and that submarine slopes at high risk of failure could be identified in this way.