P. Schmoldt, PhD - MTNet - DIAS

Contents
5.1.3. Semiconduction . . . . . . . . . . . . . . . . . . . . . . . . . . 86
5.2. Variation of electric conductivity with depth . . . . . . . . . . . . . . . . 87
5.2.1. The Earth’s crust . . . . . . . . . . . . . . . . . . . . . . . . . . 89
5.2.2. The Earth’s mantle . . . . . . . . . . . . . . . . . . . . . . . . . 91
5.2.3. The Earth’s core . . . . . . . . . . . . . . . . . . . . . . . . . . 98
5.3. Parameters controlling the conductivity of the Earth’s mantle . . . . . . . 99
6. Using magnetotellurics to gain information about the Earth 105
6.1. Recording of magnetotelluric signals . . . . . . . . . . . . . . . . . . . . 105
6.1.1. Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
6.1.2. Station setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
6.2. Processing of magnetotelluric data . . . . . . . . . . . . . . . . . . . . . 108
6.2.1. Pre-processing of the time-series data . . . . . . . . . . . . . . . 109
6.2.2. Transformation into the frequency domain . . . . . . . . . . . . . 110
6.2.3. Robust remote reference processing . . . . . . . . . . . . . . . . 111
6.3. Deriving subsurface structure using magnetotelluric data . . . . . . . . . 114
6.3.1. Analytical direct transformation . . . . . . . . . . . . . . . . . . 114
6.3.2. Forward modelling . . . . . . . . . . . . . . . . . . . . . . . . . 116
6.3.3. Inversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
II. Geology of the study area 132
7. Geology of the Iberian Peninsula 133
7.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
7.2. Betic Mountain Chain . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
7.2.1. Previous geophysical studies in the region . . . . . . . . . . . . . 136
7.3. Tajo Basin and central Spain . . . . . . . . . . . . . . . . . . . . . . . . 143
7.3.1. Tectonic evolution and characteristics . . . . . . . . . . . . . . . 143
7.3.2. Previous geophysical studies in the region . . . . . . . . . . . . . 152
7.3.3. Summary and conclusions . . . . . . . . . . . . . . . . . . . . . 165
III. A novel inversion approach for oblique geoelectric strike directions
in crust and mantle 167
8. Recovering a synthetic 3D subsurface model using lower-dimensional
inversion schemes 169
8.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
8.2. Generating synthetic 3D model data . . . . . . . . . . . . . . . . . . . . 171
8.2.1. Generating the synthetic 3D model . . . . . . . . . . . . . . . . . 171
8.2.2. Data preparation and analysis . . . . . . . . . . . . . . . . . . . 172
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