P. Schmoldt, PhD - MTNet - DIAS

10. Data inversion
Depth (km)
S
0
50
100
150
Campo de Montiel M.P. Loranca Basin N
pic020
pic019
pic017
pic015
pic013
pic011
200
200
-100 -50 0 50 100
Distance from centre of profile (km)
pic009
pic007
pic005
pic004
pic003
pic002
pic001
0
50
100
150
3D MT inversion
Tajo Basin
Resistivity log 10(Wm)
0 0.8 1.6 2.4 3.2
36ON A.D.
N
100 km
Seismic tomography
Betics Tajo Basin
dP-wave velocity
-2.5% +2.5%
Fig. 10.33.: Comparison of the isotropic 3D inversion result of PICASSO Phase I station responses in the Tajo Basin (left) and a
seismic tomography transect extracted from the global P-wave velocity model of Amaru [2007] (bottom-right); similar seismic results
are obtained by Hoernle et al. [1995], Bijwaard et al. [1998], and Villaseñor et al. [2007] for the same region (cf. Chap. 7). Location
of the PICASSO Phase I stations and course of the profile on top of the inversion mesh are shown on the top-right of this figure,
next to a map of the Iberian Peninsula in which the PICASSO Phase I profile in the Tajo Basin is indicated by a red line. Geological
regions, based on the USGS EnVision map for Europe (Figure 9.1), are shown on the top of the MT inversion model (M.P: Manchega
Plain). The location of the MT inversion model in respect to the seismic transect is indicated by the dashed black lines on top of the
seismic model. The dotted green line indicates the upper range of the low velocity region beneath the Tajo Basin (plotted on top of
the seismic as well as on the MT model). Yellow lines represent potential fluid migration paths that may originate from dehydration
of the subducting slab beneath Alboran Domain (A.D.) and Betics (indicated by high velocity feature in the seismic inset) and intrude
into the lithosphere beneath the Tajo Basin; see text for details. White dashed and dotted-dashed lines on top of the MT inversion
model indicate inferred approximate location of the crust-mantle and the lithosphere–asthenosphere boundary (LAB), respectively (cf.
Chapter 7 and Section 8.3.3). Structure at crustal depth are not strongly constrained because the focus of this isotropic 3D inversion
was on investigating mantle structures, whereas characteristics of sublithospheric regions are not strongly constrained by the inversion
due to the low signal-to-noise ratio of related impedance estimates (the location of these weakly constrained regions are indicated by
shaded areas); see text for further details.
vides useful insights about the source of the high conductivity – low velocity anomaly in
the middle and lower crust beneath the Campo de Montiel region (feature ‘f’ in Figure
10.6). In the 3D inversion result, the crustal anomaly is modelled to the west of stations
pic015 – pic019 at a depth of approximately 10 – 25 km (cf. Fig. 10.34), which is in
excellent agreement with induction arrow directions (Figure 10.12) and results of the ambient
noise tomography study by Villaseñor et al. [2007] (Figs. 7.21 and 10.11). Hence,
3D inversion is supporting previous conclusions that this high conductivity anomaly is a
relatively small-scale feature and correlated with the low seismic velocity anomaly; see
Section 10.1.5 for a discussion of this feature.
272
100
300
500
41 O N
100
300
500
Depth (km)