Abstract

Fibre-optic deformation sensing provides new opportunities for seismic data acquisition with high spatio-temporal resolution. The relative ease of deploying fibre-optic cables, or the possibility to piggyback on existing telecom infrastructure make this technology particularly attractive for environments where large numbers of conventional seismic instruments may be difficult to install. These include active volcanoes, glaciers or densely populated urban centres.

In the first, more observational part of this talk, we will present a series of case studies where Distributed Acoustic Sensing (DAS) greatly improved the location of glacial icequakes and our knowledge of ice sheet structure, enabled the observation of previously unknown volcanic tremor and resonance phenomena, and increased the number of detected seismic events by two orders of magnitude – all relative to data from existing seismometer networks.

In the second, more theoretical part, we will report on the development of a novel fibre-optic sensing system that is based on the transmission of microwave-modulated laser pulses. While being more than 10 times cheaper than most DAS systems, the microwave system allows for interrogation distances of hundreds or thousands of kilometres. We show theoretically that different segments of the fibre can have different sensitivities for deformation sensing, largely depending on fibre curvature. Data from a large-scale experiment in Athens support this theory, thereby suggesting that tomographic imaging in remote regions and in the oceans should be possible.