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Russian Geology and Geophysics

2018 year, number 8


A.I. Miroshnichenko1, N.A. Radziminovich1, A.V. Lukhnev1, F.L. Zuev1, S. Demberel2, D. Erdenezul2, M. Ulziibat2
1Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences, ul. Lermontova 128, Irkutsk, 664033, Russia
2Institute of Astronomy and Geophysics, Mongolian Academy of Sciences, Ulaanbaatar, Mongolia
Keywords: GPS measurements, crust strain, fault, seismicity, Mongolia


First results of the analysis of GPS measurement data obtained from 18 sites of two local geodynamic test grounds in the vicinity of Ulaanbaatar (Mongolia) for the period 2010-2015 have been presented. Horizontal velocity vectors are coordinated with each other in the ITRF2014 system and with the velocities from the IGS permanent station ULAB. The sites are shifted in the E-SE direction at a rate of 25-30 mm/yr, with the displacement azimuth averaging 105°. With respect to Eurasia, the vectors for most of the sites are to a certain extent S-trending, but their continued motion (2-4 mm/yr) is also oriented SE with the azimuth range 130-150. Relative horizontal velocities tend to decrease toward the southeast, with their zonal structures established within the Ulaanbaatar test ground area. The western part of the Ulaanbaatar test ground is dominated by roughly W-E extension, the elongation is ε1 = (12-16)‧10-8 yr-1. The shortening NW-SE trending strain with calculated value ε2 = 22.4‧10-8 yr-1 characterizes the test ground’s eastern part. The highest values of the maximum shear strains (εmax = (10-14)‧10-8 yr-1) form an extended area in the center of the test ground, elongated in the northeastern direction, conformably with the strike of the major geologic structures. The strain distribution pattern of the Emeelt test ground located within the eponymous seismogenic structures is characterized by the crustal elongation (5‧10-6 yr-1) trending SE-NW and less pronounced shortening in the SW-SE directions. The axial part of the fault crossing the test ground in the NW direction exhibits maximum deformations.