Modern Movements of the Crust Surface in Gorny Altai From GPS Data

Abstract

In 2000–2017, the GPS technology was first applied to study inter-seismic, co-seismic and post-seismic processes in the crust of the Altai Mountains (Gorny Altai). Our study aims at investigating the fields of displacement and deformation in the Gorny Altai region as a part of Asia.The 3D displacement fields are reconstructed for the period before the M 7.3 Chuya earthquake that occurred in the southern sector of the Altai GPS network (49° to 55°N, and 81° to 89°E)on 27 September 2003.Anomalous behavior features are discovered in the displacement orientations, as well as in the distribution of velocities and deformation in the zone of the future earthquake.The spatial displacement pattern defined for the period of co-seismic displacements corresponds to the right-lateral strike-slip along the vertical fault. The fault depth is estimated using the elastic model and the experimental data (change in displacement from 0.30 m to 0.02 m at the distances of 14 km and 84 km from the fault, respectively); it amounts to 8–10 km.The co-seismic deformation field is investigated.In the post-seismic stage (2004–2017), displacements revealedin the epicentral zone show the right-lateral strike-slip along the fault at the rate of 2 mm/yr. Therefore, two-layer viscoelastic models can be considered. The estimated viscosity of the lower crust ranges from 6×1019to 3×1020Pa×s, and the elastic upper crust thickness is 25 km. Analyzed are modern movements in the Gorny Altai region outside the Chuya earthquake area.The results of our study show that modern horizontal displacements occur in the NNW direction at the rate of 1.1 mm/yr, which is twice lower than the displacement rate before the earthquake.

Deep Structure of the Altai Mountains and Modern Gravity Field Models

“…Анализ данных по Горному Алтаю проводился с использованием поля силы тяжести в редукции Буге. Навигационные параметры для гравиметрических пунктов с точностью до сантиметров определялись с использованием двухчастотных геодезических приемников GPS типа TRIMBLE 4700 с опорой на данные пунктов геодинамической сети космической геодезии Горного Алтая [Timofeev et al, 2019]. 4.…”

“…Geodynamics & Tectonophysics 2023 Volume 14 Issue 1 Timofeev V. Yu. et al: Deep Structure of the Altai Mountains... [Nazarian et al, 2008;Timofeev et al, 2019]. Вертикальные смещения достигали максимума в области окончания разрыва и составляли несколько сантиметров.…”

Geodynamic model of the interaction between the continental lithosphere and the active continental margin in East Asia

“…Subsequently, as a result of the network growth, regional networks were combined into the Crustal Movement Observation Network of China (CMONOC), which currently has more than 4000 observation stations and covers the entire territory of mainland China [Wang and Shen, 2020]. In the last decade, measurements have also been carried out at geodynamic polygons in the Amur, Baikal, and Gorny Altai regions [Lukhnev et al, 2010;Sankov et al, 2014;Shestakov et al, 2011;Timofeev, 2014;Timofeev et al, 2019].…”