Long Period Magnetotellurics in Western Uganda

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The conductivity structure of the crust and upper mantle beneath and east of the Rwenzori mountains will be investigated with the magnetotelluric method. During 2 field surveys altogether 4 profiles (short periods, 100 km/profil) will be measured following the teleseismic sites. Additionally 10 long period sites (10-100000s) will be installed. The measurements will give a detailed 3D image of conductive features from the upper crust down to several hundred kilometers into the upper mantle. The following goals will be pursued: a) Mapping of the thickness of the sediments east of the Rwenzoris, b) investigation of the geometry and depth range of conductive faults, c) correlation of conductive structures with the seismogenic zone, d) correlation of electrical anisotropy with fault plane solutions, e) mapping of the electrical asthenosphere including anisotropy, f) investigation of conductivity mechanisms, especially the influence of water, using petrologic results, g) constraining geodynamic modelling. The modelling and interpretation of structures in the deeper crust and upper mantle will be performed in close co-operation with the teleseismic group. The complementary nature of seismologic and MT data enables to distinguish between a variety of different models concerning the ductile roots of rifting and to take into account the effects of rheology, temperature and rock composition. The interpretation of the observations will form the basis for more detailed magnetotelluric investigations during the following 3 years (year 4-6 of the Research Unit).