P. Schmoldt, PhD - MTNet - DIAS

0 km
10 km
30 km
100 km
300 km
Depth range
Depth: 0 – 300 km
90
75
60
45
30
15
0
pic041
pic040
pic037
pic035
pic033
pic031
Betic Cordillera
9.6. Compensating for distortion of the impedance tensor
pic029
pic027
pic025
pic023
CIZ
pic022
pic020
pic019
pic017
pic015
Multi-strike
(Av. RMS-misfit in brackets)
pic013
pic011
pic009
pic007
Tajo Basin
pic006
All stations Tajo Basin
51.5 (1.6) 51.4 (1.5)
Fig. 9.6.: RMS misfit for different geoelectric strike directions of the stations recorded during PICASSO Phase I, using data in the
Niblett-Bostick depth range 0 – 300 km; shown in the inset. Also shown in the top right corner is the optimal common geoelectric
strike direction clockwise from North calculated for all stations and for stations in the Tajo Basin only; indicated by the dashed white
line in the main plot. Assignment of stations to the different geological regions, displayed on the bottom of the plot, is based on their
location in respect to geological units of the USGS EnVision map for Europe (Fig. 9.1), CIZ: Central Iberian Zone, part of the Iberian
Massif. See text for further details.
in geoelectric strike characteristics described in the following paragraphs. For a 2D subsurface,
satisfactory multi-strike directions should coincide with low RMS misfits for the
same direction at a number of adjacent stations, bounded by higher RMS misfits for other
directions. Cases where the RMS misfit is low for most directions, on the other hand,
indicate a rather 1D nature of the subsurface. In the following paragraphs geoelectric
strike direction is determined for different depth ranges in order to investigate whether the
best-fitting direction varies for individual regions in crust and mantle.
Complete depth range
Initially, the RMS misfit for different directions is calculated for the whole depth range
spanning from 0 to 300 km, revealing an unsystematic distribution of the RMS misfit (cf.
Fig. 9.6). Low RMS misfits at stations pic013 – pic017 and pic023 – pic025 are due to the
truncation of their long-period data affected by EM noise sources, as described in Section
9.4. The low RMS misfit of station pic009, on the other hand, observed throughout the
whole frequency range, is due a higher degree of uncertainty of the responses for this
station. Multi-strike analysis yields optimal strike direction and RMS misfit (in brackets)
of N51.5E (1.6) and N51.4E (1.5) for the whole profile and the Tajo Basin, respectively;
which however, is not significant given the observed unsystematic RMS misfit distribution
along the profile.
Crust and mantle depth
As a second step, the depth range is divided into crust and mantle regions spanning from
0 km to 30 km and 35 km to 200 km, respectively (Fig. 9.7); therein, Moho depths of
32 km derived by seismic reflection data (cf. Sec. 7.3.2) are used as crustal-thickness
proxy with a small error margin. The crustal depth range exhibits an unsystematic RMS
misfit distribution and a multi-strike direction of N58.0E (1.3 av. RMS misfit) and N51.2E
(1.5 av. RMS misfit) for the whole profile and the Tajo Basin, respectively.
pic005
pic004
pic003
pic002
pic001
RMS
misfit
3
2
1
0
211