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| Titel |
Impact of permeability on seismoelectric transfer function of P waves |
| VerfasserIn |
J. Holzhauer, C. Bordes, F. Oppermann, D. Brito, U. Yaramanci |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250064135
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| Zusammenfassung |
| Recent developments in the understanding of seismoelectrics have shown its potential
relevance for porous media characterization with particular focus on permeability
estimations. According to promising theoretical and numerical studies, permeability should
influence the seismoelectric transfer function at higher frequencies. The dynamic
seismoelectric transfer function E(Ï)/ ü(Ï), where E relates to the coseismic electric field
induced by the seismic particle acceleration ü, is expected to increase with increasing
permeabilities when crossing the Biot transition frequency. Still, only few experiments have
been developed on that matter so far.
To address the transfer function dependence on permeability, we adapted a column
experiment to comply with steady-state permeability estimations. These observations were
run in-situ, during the fluid-balancing phase prior to seismoelectric measurements. The 50
cm-long column had previously been carefully filled with perfectly rounded glass beads. The
use of sorted glass beads is expected to achieve similar porosities reproducible
throughout the experiment, opposed to varying permeabilities depending on the
introduced particle size. The acoustic source delivered compressional waves with
an optimal effect limited to the [1-3] kHz frequency range. These limitations are
due to strong seismic attenuation in uncompacted porous media on one side, and
to the dilemma of observing propagation in downsized laboratory setup on the
other.
First results validated the experimental protocol in terms of porosity/permeability
independence: for particle size varying between 100 μm and 500 μm, permeability varied by
a factor 20, with a maximum by 5.10-11 m2, while porosity remained by 39 ± 2 % during
the whole experiment. Further investigations are being led regarding the normalised transfer
function, corrected for both the fluid conductivity and the seismic energy. For that purpose,
we compare the dependence of our measured transfer function on permeability at a given
frequency, to that predicted by synthetics, computed using our experimental permeabilities. |
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