Geoelectric Section of the Coastal Region of the Chukchi Sea near the Cape Schmidt Observatory

Abstract

Abstract —This paper presents the results of 3D inversion of magnetovariational tippers obtained at the Cape Schmidt observatory via digital processing of geomagnetic variation records performed by the MAGDAS-I magnetometer. 3D tipper frequency inversion is carried out using the ModEM software. The result is horizontal and vertical sections in the coastal strip of the Chukchi Sea in a spatial region with a dimension of 300 × 300 × 200 km along the X, Y, and Z axes, respectively. The geoelectric section of the investigated region contains both surface and deep conductive blocks located at different azimuths relative to a measurement point. The surface conductive anomaly near the observatory with a resistivity of ≈3 Ohm·m is located in the southeast direction at depths of a few hundred meters. The other conducting inhomogeneity is larger and located in the same direction, but at a distance of about 25–30 km and depths of 4–16 km. The resistivity of its central region at a depth of 8 km is equal to 1 Ohm·m. From the side of the South Chukchi Depression, there is an inclined conductive block in the Chukchi Sea, located closer to the coast to the bottom of the Earth’s crust, and the maximum resistivity of this block in the central part at a depth of 20 km is equal to ≈7 Ohm·m. The most noticeable feature of the section is a massive upper-mantle conductive block under the continent at depths of 50–120 km with a resistivity of 3–4 Ohm·m in the central part at depths of 70–85 km. Deeper into the continent, the block is slightly inclined to the southeast. There are visible conductive regions that connect this block with upstream conductive formations. The epicenters of weak crustal earthquakes recorded in the region are located above the northwestern marginal part of the upper-mantle block, including its central region. Possible mechanisms of high electrical conductivity of anomalous blocks are discussed.