Fibre-optic cables can be used to detect earthquakes and other ground movements. The data cables can also pick up seismic signals from hammer shots, passing cars or wave movements in the ocean. This is the result of a study published in Nature Communications.
ÍSOR scientists Hanna Blanck and Gylfi Páll Hersir are among the co-authors and carried out the investigation together with colleagues from the UK and from Research Instituts in, Berlin, Germany, and Potsdam, Germany. The main authors are Philippe Jousset and Thomas Reinsch from GFZ German Research Centre for Geosciences.
The scientists sent pulses of laser light through an optical fibre, which was part of a 15 kilometer long cable deployed in 1994, within the telecommunication network on Reykjanes peninsula, SW Island, crossing a well-known geological fault zone in the rift between Eurasian and American tectonic plates. The light signal was analyzed and compared to data sets from a dense network of seismographs. The results amazed even experts: “Our measurements revealed structural features in the underground with unprecedented resolution and yielded signals equaling data points every four meters”, says Philippe Jousset from the GFZ. Although the method is not new in other applications (it is used for years in boreholes to measure temperature changes for reservoir monitoring), the team is the first worldwide that carried out such measurements along the surface of the ground for seismological objectives, and with such a long cable.
Their current study not only shows well-known faults and volcanic dykes. The scientists also found a previously unknown fault, below the ground surface. Furthermore, the team measured subsurface deformation taking place over a period of several minutes. Small local earthquakes, waves originating from large distant quakes, and microseism of the ocean floor were also recorded via fibre-optic cable. The advantages of the new method are enormous as there are countless fibre-optic cables spanning the globe in the dense telecommunication network. Especially beneath megacities with high seismic hazards, such as San Francisco, Mexico City, Tokyo, or Istanbul, and many others, such cables could provide a cost efficient and widely spread addition to existing seismological measuring devices.
Link and journal reference:
Jousset, P., Reinsch, T., Ryberg, T., Blanck, H., Clarke, A., Aghayev, R., Hersir, G.P., Henninges, J., Weber, M., Krawczyk, C.M., 2018. Dynamic strain determination using fibre-optic cables allows imaging of seismological and structural features. Nature Communications.