An Integrated Geophysical Approach for Permafrost Delineation at a Key site in the Pechora River Delta
S.Yu. Davydenko1,2, M.S. Sudakova1,2, M.R. Sadurtdinov1, A.G. Skvortsov1, A.M. Tsarev1, G.V. Malkova1
1 Earth Cryosphere Institute, Tyumen Scientific Centre, Siberian Branch of the Russian Academy of Sciences, Tyumen, Russia
2Lomonosov Moscow State University, Faculty of Geology, Moscow, Russia
Keywords: cryolithozone, permafrost, ground penetrating radar, ground penetrating radar sounding, seismic exploration, electrical resistivity tomography.
Abstract
The article presents the results of applying an integration of geophysical methods (ground-penetrating radar in profiling and sounding modes, seismic reflection survey using SH-waves, electrical resistivity tomography, and thermometry) to determine the geocryological section at the Kumzha research station in the Pechora River delta (Nenets Autonomous Okrug). Fieldwork was carried out in August 2023 and from late July to early August 2024. The application of this integrated approach made it possible to determine the position of the table and base of the permafrost at depths of 5–8 m and 20–22 m, respectively; establish the thickness of the frozen layer as 11–16 m; identify the boundary between frozen sand and clays within the permafrost at a depth of 10–12 m; and determine the location of the island permafrost. Transverse SH-wave velocities were determined as follows: 200–300 m/s in the seasonally thawed layer (active layer), 1300 m/s in the frozen sand, and 820 m/s in the lower frozen clay layer. The electrical resistivity values are: 300–1500 Ohm·m for the seasonally thawed layer (sand), >10,000 Ohm·m for frozen sand, 500–2000 Ohm·m for frozen loams, and 5–100 Ohm·m for thawed clays. The electromagnetic wave velocity in the aeration zone (dry sands) was 10–11 cm/ns, decreasing to 6 cm/ns in fully saturated sands and increasing to 11 cm/ns in frozen sands. The integration of these methods ensured mutual verification of the geological boundaries (taking into account drilling and thermometry data) and enabled the construction of a reliable petrophysical–geological model of the geocryological section.
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