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Author
Date
2021Type
- Doctoral Thesis
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Abstract
This thesis investigates the potentials of Distributed Acoustic Sensing in seismology. Distributed
Acoustic Sensing (DAS) is an emerging method to measure strain along optical
fibers. DAS systems are capable of measuring acoustic and elastic waves propagating along
the fiber, and hence can be used as a seismological receiver, where its measurements are
related to the symmetric part of the displacement gradient tensor.
To investigate the potentials of DAS in seismic imaging, this thesis first establishes the
properties of DAS measurements in an extensive instrument response study utilizing data
from a wide range of experiments conducted as part of this thesis.
Confirming the suitability of DAS measurements for seismological applications from the
instrument response study, this thesis then connects strain to rotational measurements,
related to the anti-symmetric part of the displacement gradient tensor, and introduces the
concept of obtaining rotational observations from DAS recordings.
This thesis then extends the existing theory of generalized ambient noise interferometry
from displacements to gradient measurements. We show the potential to combine different
seismic observables within the framework of interferometry, accounting for the observational
effect on the interferometric wavefield due to spatial gradients. With the extended
formulation of interferometry, we use adjoint-based methods to incorporate spatial gradient
observations into full waveform ambient noise inversion.
Based on theoretical investigations, numerical simulations and real-world examples, this
thesis ultimately aims to incorporate gradient observations into existing geophysical workflows
and to develop new methods utilizing such gradient observations, expanding the fields
of theoretical, numerical and observational seismology. Show more
Permanent link
https://doi.org/10.3929/ethz-b-000474545Publication status
publishedExternal links
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Contributors
Examiner: Fichtner, Andreas
Examiner: Schmelzbach, Cédric
![cc](/themes/Mirage2//images/orcid_icon.png)
Examiner: Edme, Pascal
Examiner: Igel, Heiner
Publisher
ETH ZurichSubject
SEISMOLOGY (GEOPHYSICS); Seismology; Ambient seismic noise; Seismology; Fiber-optic sensing; Seismology; Distributed Acoustic Sensing; Full waveform inversion; SEISMIC INSTRUMENTS (APPLIED GEOLOGY AND GEOPHYSICS); SEISMIC INTERFEROMETRY (APPLIED GEOLOGY AND GEOPHYSICS)Organisational unit
03971 - Fichtner, Andreas / Fichtner, Andreas
Related publications and datasets
Has part: https://doi.org/10.3929/ethz-b-000416808
Is derived from: http://hdl.handle.net/20.500.11850/455639
Is derived from: https://doi.org/10.3929/ethz-b-000320899
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