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Joint inversion of electrical resistance and GPR traveltime data applied to unsaturated sandstone
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
(English)Manuscript (Other (popular science, discussion, etc.))
Identifiers
URN: urn:nbn:se:uu:diva-93414OAI: oai:DiVA.org:uu-93414DiVA: diva2:166879
Available from: 2005-09-01 Created: 2005-09-01 Last updated: 2010-12-21
In thesis
1. Characterization of Hydrogeological Media Using Electromagnetic Geophysics
Open this publication in new window or tab >>Characterization of Hydrogeological Media Using Electromagnetic Geophysics
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Radio magnetotellurics (RMT), crosshole ground penetrating radar (GPR), and crosshole electrical resistance tomography (ERT) were applied in a range of hydrogeological applications where geophysical data could improve hydrogeological characterization.

A profile of RMT data collected over highly resistive granite was used to map subhorizontal fracture zones below 300m depth, as well as a steeply dipping fracture zone, which was also observed on a coinciding seismic reflection profile. One-dimensional inverse modelling and 3D forward modelling with displacement currents included were necessary to test the reliability of features found in the 2D models, where the forward models did not include displacement currents and only lower frequencies were considered.

An inversion code for RMT data was developed and applied to RMT data with azimuthal electrical anisotropy signature collected over a limestone formation. The results indicated that RMT is a faster and more reliable technique for studying electrical anisotropy than are azimuthal resistivity surveys.

A new sequential inversion method to estimate hydraulic conductivity fields using crosshole GPR and tracer test data was applied to 2D synthetic examples. Given careful surveying, the results indicated that regularization of hydrogeological inverse problems using geophysical tomograms might improve models of hydraulic conductivity.

A method to regularize geophysical inverse problems using geostatistical models was developed and applied to crosshole ERT and GPR data collected in unsaturated sandstone. The resulting models were geologically more reasonable than models where the regularization was based on traditional smoothness constraints.

Electromagnetic geophysical techniques provide an inexpensive data source in estimating qualitative hydrogeological models, but hydrogeological data must be incorporated to make quantitative estimation of hydrogeological systems feasible.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. 65 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 86
Keyword
Geophysics, Hydrogeophysics, radio magnetotellurics, ground penetrating radar, electrical resistance tomography, inversion, regularization, geostatistics, electrical anisotropy, fractured rock, Geofysik
National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-5912 (URN)91-554-6325-8 (ISBN)
Public defence
2005-09-23, Axel Hambergsalen, Geocentrum, Villav. 16, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2005-09-01 Created: 2005-09-01 Last updated: 2009-03-24Bibliographically approved

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Pedersen, Laust B.

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