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| Titel |
Time-domain Electromagnetic Exploration of Salt Islands: Three-dimensional Modelling and Field Results |
| VerfasserIn |
P. Bauer-Gottwein, B. R. N . Gondwe, L. Christiansen, L. Kgotlhang, D. Herckenrath, S. Zimmermann |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250022283
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| Zusammenfassung |
| The time-domain electromagnetic method (TDEM) has been widely used in groundwater
exploration and geological mapping applications. TDEM measures the subsurface electrical
conductivity, which is strongly correlated with groundwater salinity. TDEM thus
offers cheap and non-invasive ways to map saltwater intrusion and groundwater
salinization. Typically, TDEM data is interpreted using 1D layered-earth models of the
subsurface. However, most saltwater intrusion and groundwater salinization phenomena
produce eminently three-dimensional anomalies. To fully exploit the information of
TDEM data in this context, three-dimensional modeling of the TDEM response is
required.
We present a finite-element solution for three-dimensional forward modeling of TDEM
responses from arbitrary subsurface electrical conductivity distributions. As an application
example, the groundwater salinization process on islands in the Okavango Delta is simulated
using a variable-density flow and salinity transport model. The transport model
outputs are subsequently converted to TDEM responses using the 3D TDEM forward
code.
A field dataset of ground-based and airborne TDEM data from a selected Okavango Delta
island is presented. The TDEM field data cannot be interpreted in terms of 1D layered-earth
models, because of the strongly three-dimensional nature of the salinity anomaly under the
island. A 3D interpretation of the field data allows detailed and consistent mapping of this
anomaly. |
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