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.