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Titel |
On the use of a laser ablation as a laboratory seismic source |
VerfasserIn |
Chengyi Shen, Daniel Brito, Julien Diaz, Deyuan Zhang, Valier Poydenot, Clarisse Bordes, Stephane Garambois |
Konferenz |
EGU General Assembly 2017
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Medientyp |
Artikel
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Sprache |
en
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 19 (2017) |
Datensatznummer |
250149599
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Publikation (Nr.) |
EGU/EGU2017-13963.pdf |
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Zusammenfassung |
Mimic near-surface seismic imaging conducted in well-controlled laboratory conditions is
potentially a powerful tool to study large scale wave propagations in geological media by
means of upscaling. Laboratory measurements are indeed particularly suited for tests of
theoretical modellings and comparisons with numerical approaches.
We have developed an automated Laser Doppler Vibrometer (LDV) platform, which is
able to detect and register broadband nano-scale displacements on the surface of various
materials. This laboratory equipment has already been validated in experiments where
piezoelectric transducers were used as seismic sources. We are currently exploring a new
seismic source in our experiments, a laser ablation, in order to compensate some drawbacks
encountered with piezoelectric sources.
The laser ablation source is considered to be an interesting ultrasound wave generator
since the 1960s. It was believed to have numerous potential applications such as the
Non-Destructive Testing (NDT) and the measurements of velocities and attenuations in solid
samples. We aim at adapting and developing this technique into geophysical experimental
investigations in order to produce and explore complete micro-seismic data sets in the
laboratory.
We will first present the laser characteristics including its mechanism, stability,
reproducibility, and will evaluate in particular the directivity patterns of such a seismic
source. We have started by applying the laser ablation source on the surfaces of
multi-scale homogeneous aluminum samples and are now testing it on heterogeneous and
fractured limestone cores. Some other results of data processing will also be shown,
especially the 2D-slice V P and V S tomographic images obtained in limestone
samples.
Apart from the experimental records, numerical simulations will be carried out for both
the laser source modelling and the wave propagation in different media. First attempts will be
done to compare quantitatively the experimental data with simulations. Meanwhile, CT-scan
X-ray images of these limestone cores will be used to check the relative pertinences of
velocity tomography images produced by this newly developed laser ablation seismic source. |
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