Dynamic strain determination using fibre-optic cables allows imaging of seismological and structural features

Philippe Jousset,Jan Henninges,Gylfi P Hersir,Trond Ryberg,Charlotte M Krawczyk,Andy Clarke,Hanna Blanck,Rufat Aghayev,Thomas Reinsch,Michael Weber

doi:10.1038/s41467-018-04860-y

Abstract

Natural hazard prediction and efficient crust exploration require dense seismic observations both in time and space. Seismological techniques provide ground-motion data, whose accuracy depends on sensor characteristics and spatial distribution. Here we demonstrate that dynamic strain determination is possible with conventional fibre-optic cables deployed for telecommunication. Extending recently distributed acoustic sensing (DAS) studies, we present high resolution spatially un-aliased broadband strain data. We recorded seismic signals from natural and man-made sources with 4-m spacing along a 15-km-long fibre-optic cable layout on Reykjanes Peninsula, SW-Iceland. We identify with unprecedented resolution structural features such as normal faults and volcanic dykes in the Reykjanes Oblique Rift, allowing us to infer new dynamic fault processes. Conventional seismometer recordings, acquired simultaneously, validate the spectral amplitude DAS response between 0.1 and 100 Hz bandwidth. We suggest that the networks of fibre-optic telecommunication lines worldwide could be used as seismometers opening a new window for Earth hazard assessment and exploration.

Highlights

Natural hazard prediction and efficient crust exploration require dense seismic observations both in time and space
Field studies on vertical seismic profile (VSP) data show that the frequency spectrum recorded with distributed acoustic sensing (DAS)/distributed vibration sensing (DVS) is comparable to conventional geophone data[32], where the bandwidth of the seismic record is limited by the minimum frequency generated by the source, e.g. >5–10 Hz
Over a broad frequency band, we show that recorded strain rate signals are meaningful: after we corrected for the instrumental response of both DAS and seismometer data, the DAS signals accurately match those derived from the seismometers

Summary

Introduction

Natural hazard prediction and efficient crust exploration require dense seismic observations both in time and space. Seismic and ground-motion datasets quality (spatial density, accuracy, bandwidth, etc.) determines our ability to characterize crustal media properties distribution, seismic source processes and wave propagation mechanisms. These are mandatory for acute natural hazard assessment[1,2,3], for efficient resource exploration[4], and for structural health monitoring and security[5]. Accurate wavefields in space are frequently acquired by increasing the density of instruments at the surface, such as network deployment of cheap geophones[19] Those studies address mainly local structures (typically several km2) and use limited frequency band (>4 Hz).

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Conclusion