P. Schmoldt, PhD - MTNet - DIAS

10. Data inversion
Depth (km)
Depth (km)
(a)
(b)
S N
Campo de Montiel M.P.
Loranca Basin
0
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300
0
50
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pic020
pic019
pic011
pic009
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pic005
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0 16 32 48 64 80 96 112 128 144
Distance (km)
log 10
(Wm)
0 1.1 2.2 3.3
Fig. 10.19.: Models of the Tajo Basin subsurface used as starting model for anisotropic 2D inversion. The models contain crustal
structures derived by the isotropic 2D inversion for the Tajo Basin crust and either (a) a homogeneous 100 Ωm halfspace or (b) a
100 Ωm lithospheric-mantle and a 10 Ωm asthenosphere to represent the mantle.
6.3); thereby masking information in the dataset. In particular, data for the longest periods
are not well constraint due to their higher uncertainty levels. Accordingly, sensitivity
to the asthenospheric region is low and regularisations are chosen to fit the characteristics
of this region; i.e. (a) increased horizontal smoothing (α = 3) since the eLAB can
be assumed to exhibit relatively low vertical variation, (b) intermediate global smoothing
(τ = 6) to avoid loosing the electric resistivity decrease at the LAB due to too high
smoothing, and (c) electric resistivity gradient regularisation because the asthenosphere
is commonly assumed as a region of relatively homogeneous electric resistivity.
Corresponding to findings of the synthetic model study presented in Chapter 8, results
of the anisotropic 2D inversion approach are shown using electric resistivity values of
the direction orthogonal to the profile (ρXX). Electric resistivity models for the opposite
direction (ρYY) exhibit implausible low values (cf. Fig. 10.21) and are not considered
representative for the Tajo Basin mantle. Inversion models obtained using either a halfspace
or two layers to represent the mantle region (top and bottom plot in Figure 10.19,
respectively) are virtually identical (cf. Fig. 10.21), thereby indicating robustness of the
inversion process. Moreover, both models exhibit electric resistivity values ≥ 100 Ωm for
the region associated with the asthenosphere; thus, indicating that an electrically conduc-
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