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Abstract:
Recent developments in modelling of Geomagnetically Induced Currents (GIC) show that accurate 3D Earth’s electrical conductivity model is required in order to estimate accurately electric fields. In turn properly estimated electric fields at the Earth’s surface lead to better estimation of electric currents in power/communication infrastructure. The Fennoscandia in general is prone to significant GIC events due to proximity of sources at high latitudes and due to the fact that the strength of the electric field is significantly amplified over generally resistive Fennoscandian lithosphere, intersected by numerous conductive anomalies. These anomalies together with surrounding ocean give rise to even larger electric fields (normal electric field is discontinuous). Conductance map (SMAP) of entire Fennoscandia and surrounding regions was developed by Korja et al. during international BEAR project (1997-2003). The map was based on all available at the time geological and geophysical information (including airborne EM data) and primarily sparse magnetotelluric data(interpreted using 1D or 2D assumptions). Several magnetotelluric surveys were conducted in Fennoscandia since that time, especially in the Northern Fennoscandia. We present the most recent 3D models which are further integrated to update the SMAP. We also consider and propose further plans to cover entire Fennoscandia (perhaps entire Europe) with “sufficiently” dense MT measurements. Furthermore, we compare estimates of geoelectric fields on regional scale using earlier SMAP and updated more detailed SMAP.
