Study of Crustal Displacement Fields in Primorie by Satellite Geodesy Methods

—This work presents the results of GPS observations (2003–2020) carried out in PrimorskyKrai (aka the Primorie) and Khabarovsk Krai in southeastern Russia. The objectives of our study were to obtain displacement velocities, to test the relation of current velocities with seismicity, with the specific features of the geological structure of the Primorie, and to study the rheological parameters of the crust and asthenosphere at the continental margin. This paper analyzes the results of measurements made in the Primorie at the Central Sikhote-Alin fault. The study includes the effects of the Tohoku-Oki earthquake in Japan with magnitude М = 9 which occurred on March 11, 2011. The zone of coseismic and postseismic displacements extends to a distance of over 1000 km from the epicenter. The postseismic decay of the long-term horizontal and vertical displacements allow us to estimate the relaxation time for the elastic-viscous model. With the decay times of 4 to 8 years, the viscosity of the lower layer in the two-layer rheological model is estimated at 8 × 10 18 –3 × 10 19 Pa s. Using the bending model of the Earth’s surface and the bottom of the Sea of Japan, we estimated the thickness of the elastic upper part of the Earth’s crust in the continent–ocean contact zone at 20–25 km.