EPOS-eNLarge will provide central access to fibre optics data. What data, you wonder? Central access? We’ve asked ORFEUS Data Centre director Reinoud Sleeman of KNMI about this.
Q: What are fibre optics data?
A: Optical fibres are made from either glass or plastic and are used to transmit light over long distances. They can be as thin as a human hair and are sensitive for small variations in strain or temperature. Such changes in the fibre disturb the transmission of light and cause back-scattering. Often these fibres are buried in the subsurface where strain variations may occur, for example, due to the passing of seismic waves after an earthquake. Measuring of the back-scattering can thus monitor seismic waves, which carry information about the subsurface.
As the fibre sensing technology can measure continuously throughout the complete length of the fibre, it is also called distributed sensing. Essentially, the fibre itself is the sensor. Depending on the specifics of the technique it can measure variations in vibro-acoustics (Distributed Acoustic Sensing (DAS)), strain (Distributed Strain Sensing (DSS)) or temperature (Distributed Temperature Sensing (DTS)). Fibre sensing can be applied with existing standard telecommunications fibres.
Q: What could we use it for?
A: Fibre optics sensing provides an unprecedented opportunity for very dense, seismic monitoring of the surveyed area. Applications, amongst others, are the detection and location of (local) earthquakes, imaging of the shallow surface structure, geophysical hazards assessment (e.g. volcanic activity) and micro-seismicity monitoring in oil and gas exploration. DAS is also used to monitor geothermal systems (e.g. like the geothermall well to be installed in Delft) as well as the injection of carbon dioxide in carbon storage projects. Industry applications are the monitoring of objects (e.g. bridges) and vital areas in our infrastructure (e.g. airports, railways, power plants).
Q: “Central data access” – how does that work?
A: For decades the international, seismological community aimed for standardization of data, products and open access services. The coordination of this approach in Europe takes place within ORFEUS, a European organization for seismologic waveform data. All this work evolved into a mature, distributed infrastructure for seismological data. In Europe, the main seismological waveform archives are connected in the European Integrated Data Archives (EIDA) which offers transparent access to seismic data in European archives, including seismic data at KNMI. EPOS-eNLarge will add Fibre Optics data to this infrastructure.
Q: When can I download the data?
A: The challenges in this project for fibre optics sensing data are to handle the huge amount of data that is collected with this technique and to make these data efficiently available to the research community. These challenges require international coordination to standardize processing and archiving of such data, as well as the services to collect these data. So it may take a few years before this service goes live. But – given the wide applications of these data, providing central access to these will be a key development. So we’re all very keen to get started.