Introduction to Interferometry of Fiber Optic Strain Measurements

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Authors

Eileen R Martin, Nathaniel Lindsey , Jonathan Ajo-Franklin , Biondo Biondi

Abstract

Distributed acoustic sensing (DAS) measures the average axial strain (strain rate) along a subset of a fiber optic cable, as opposed to the particle displacement (velocity) at a particular small point sensor. In shifting from measuring a vector field to a tensor field, DAS changes the directional sensitivity of measurements of every type of seismic wave when compared to single component geophones, particularly Love and S waves.We show this through theoretical analysis of planar Rayleigh, Love, P- and S-waves over both infinitesimally small and realistic gauge lengths. We extend the analysis of individual sensor detection of surface plane waves waves to inter-receiver cross-correlations of these detections. Finally we simulate random sources distributed around particle velocity and axial strain sensors in several configurations. The extraction of Rayleigh wave signals from ambient noise interferometry is more straightforward than Love wave signals, but with some receiver geometries and source distributions both Rayleigh and Love wave arrival times may be extracted.

DOI

https://doi.org/10.31223/osf.io/s2tjd

Subjects

Applied Mathematics, Earth Sciences, Geophysics and Seismology, Other Applied Mathematics, Physical Sciences and Mathematics

Keywords

Distributed acoustic sensing, ambient noise interferometry, fiber optic sensors, Green's function estimation, imaging science

Dates

Published: 2018-06-14 22:54

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License

CC BY Attribution 4.0 International

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