Study of the Crustal Displacement Fields by Space Geodesy Method at the Primorie

Abstract

This work presents the results of GPS observations (2003–2020) carried out in Primorsky Krai (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 M = 9, which occurred on March 11, 2011. The zone of coseismic and postseismic displacements extends to a distance of over 1,000 km from the epicenter. The postseismic attenuations of the multi-year horizontal and vertical displacements allow us to estimate the relaxation time for the elastic-viscous model. With attenuation times of 4 to 8 years, the following viscosity values were obtained for the lower layer according to the two-layer rheological model:   8 × 1018–3 × 1019 Pa s. Using the bending model of the Earth’s surface and the bottom of the Sea of Japan, we estimated the thickness (20–25 km) of the elastic upper part of the Earth's crust in the continent–ocean contact zone.