Geophysical research: article

M.S. Gridchina 1
G.M. Steblov 2
I.S. Vladimirova 4 A.V. Basmanov 1
1 PLC “Roskadastr” 2 Institute of Earthquake Prediction Theory and Mathematical Geophysics, Russian Academy of Sciences 3 Schmidt Institute of Physics of the Earth, Russian Academy of Sciences 4 Shirshov Institute of Oceanology, Russian Academy of Sciences
Journal: Geophysical research
Tome: 24
Number: 4
Year: 2023
Pages: 81-96
UDK: 550.3, 551.24
DOI: 10.21455/gr2023.4-5
Full text
Keywords: geodynamics, Global Navigation Satellite Systems (GNSS), coupling coefficient, fault-block kinematics, Sakha-lin Island.
Аnnotation: Modeling of the movements at the contact of the Amur and Okhotsk plates within the Sakhalin Island was per-formed using repeated satellite measurements on Sakhalin Island and the nearest continental zone for the peri-od of 2016–2021, as well as previously published data. When modeling fault-block kinematics, well-known relations were used to calculate inverse movements for buried rectangular dislocations in an elastic medium, implemented in the TDEFNODE software package. In the process of modeling the movements, the measured horizontal components of GNSS (Global Navigation Satellite System) velocities, the boundary and the mutual kinematics of the Amur and Okhotsk relative to the North American Plate according to the NNR-MORVEL56 mod-el were used as input data. This approach revealed repeated deviations in the direction of the simulated dis-placements of the Earth's surface from the observed ones, which can be explained by the discrepancy between the a priori specified kinematics of the blocks and the observed movements. To eliminate the systematic discrepancy, it was necessary to allow of the possibility of clarifying the mutual kinematics of the blocks. The repeated calculations, with the same input data but in a problem formulation that allowed redefinition of block kinematics, led to suppression of systematic discrepancies between the model and measured displacements while maintaining the random scatter. The movement parameters of the Amur and Okhotsk plates, refined during the modeling, show typical slight differences from the movement parameters of the corresponding large lithospheric plates - the Eurasian and North American plates, from which they are distinguished into independent blocks in modern constructions. The calculated coupling coefficients in the Sakhalin segment of the interplate boundary reach maximum values at depths 20-30 km. The obtained coupling distribution at the plate contact is compared with the sources of the largest earthquakes in the last 30 years in the considered area – Neftegorsk (May 27,1995) and Uglegorsk (April 04, 2000) earthquakes, which were found to be associated with zones of maxi-mum coupling and coupling high gradient, both in the dip and strike directions.
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