P. Schmoldt, PhD - MTNet - DIAS

9. Data collection and processing
Parameter Value
Intervals per decade 4
Step width along profile ≈ 5.5. km
Interpolation radius 7
Spline weight 7
Smoothing factor 7
Tab. 9.4.: Gridding parameters used to create the pseudo-sections (Figs. 9.12 and 9.13) from the PICASSO Phase I datasets
at the LAB, are mistaken for 2D structural strike (cf. Sec. 4.1.3).
9.6.2. Decomposition of the impedance tensor
The aim of this study is, among others, the investigation of lithospheric-mantle structures.
Therefore, two datasets are derived through decomposition of the original dataset: one
according to the geoelectric strike of the crust (N40.9W), and a second according to the
geoelectric strike direction of the Tajo Basin mantle (N29.4E). No further separation of
the mantle is made, e.g. into lithospheric and asthenospheric regions, owing to the lower
resolution to structures below the LAB. The two resulting datasets can be used for separate
inversion during investigation of crust and mantle structures (Ch. 10).
After geoelectric strike directions for crust and mantle of the Tajo Basin are determined,
common distortion parameters for each region are derived for the stations associated
with the basin (pic001 – pic020), using the program strike by McNeice and Jones
[2001]. Therein, parameters are derived in the Niblett-Bostick depth range (cf. Sec. 6.3.1)
0.003 m to 30 km and 35 km to 350 km, related to crust and mantle regions, respectively.
Resulting parameters are used to decompose the impedance tensor of each station into
TE and TM mode contributions, wherein uncertainty levels are determined on a statistical
base.
9.7. Analysis of TE and TM mode response data
Data of the TE and TM mode can be visualised by so-called ‘pseudo-sections’. Pseudosections
are obtained through gridding of MT station period–resistivity (and period–
phase) data under consideration of the station locations along the profile. For the PI-
CASSO Phase I profile pseudo-sections are created for TE and TM modes of both, the
dataset decomposed for the crustal strike direction (N40.9W, Figure 9.12) and the dataset
decomposed for the mantle strike direction (N29.4E, Figure 9.13). Parameters used for the
gridding are summarised in Table 9.4. The pseudo-sections from the dataset decomposed
in respect to the crustal geoelectric strike direction will in the following be referred-to as
‘crustal strike pseudo-sections’, whereas the opposite case will be referred to as ‘mantle
strike pseudo-sections’ (Fig. 9.13).
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