P. Schmoldt, PhD - MTNet - DIAS

11.2. PICASSO Phase I investigation
is not yet optimised or adapted for parallel processing; thus, computation time of
this algorithm is considerable long, limiting the realisation to a very small number
of impedance estimates and making its application to datasets of the scale of the
PICASSO Phase I project unfeasible.
• Incorporation of “anisotropy zones” in the inversion algorithm; i.e. constraining
anisotropy to a different degree for certain parts of the inversion model, similar to
“tear zones”, which are already incorporated in current algorithms, e.g. by Rodi
and Mackie [2001].
Respective suggestions regarding enhancements of the anisotropic 2D inversion codes
have been made to the authors [R. Mackie, J. Pek, Pers. Comm., 2011], and their implementation
will enable future studies to investigate applicability of this novel approach to
more complex subsurface cases. In addition, it is suggested to employ the approach in a
wide range of synthetic and real model studies in order to further asses its performance.
11.2. PICASSO Phase I investigation
11.2.1. Summary and conclusion
For the PICASSO Phase I investigation, magnetotelluric (MT) data were acquired along
an approximately 400 km long and north-south oriented profile in south-central Spain,
crossing the Tajo Basin and the eastern Betic Cordillera regions. Deep-probing investigations
of Iberia, particularly in its central regions, are currently very sparse with previous
investigations mostly focussing on the boundaries of the peninsula, namely the Pyrenees,
the Betic Cordillera, and the Cantabrian Mountains as well as the southwestern region
of the Iberian Massif. Detailed a priori information about subcrustal structures were
previously limited to global or European-scale seismic tomography studies. Information
about the electric resistivity distribution from the PICASSO Phase I investigation provides
enhanced insights into the geological processes that formed the Iberian Peninsula
subsurface.
The PICASSO Phase I investigation was complicated by low signal-to-noise ratios in
some parts of the dataset, originating from exceptionally low solar activity during data acquisition
and the well-developed DC railway line network in Spain. A range of advanced,
robust data processing codes were used and deliberate rejection of corrupted impedance
tensor estimates had to be carried out to provide a reliable dataset for subsequent analysis
and modelling.
Varying geoelectric strike directions were determined, both along the PICASSO Phase
I profile and with depth. For the Tajo Basin, constituting the northern region of the profile,
a NW-SE oriented strike direction was determined for the crust and a NNE-SSW direction
for the mantle. For the Betics region, located to the south of the PICASSO Phase I
profile, an approximately E-W oriented geoelectric strike direction was inferred, but the
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