Геодинамика и тектонофизика (Mar 2016)

FOCAL MECHANISMS OF EARTHQUAKES AND STRESS FIELD OF THE CRUST IN MONGOLIA AND ITS SURROUNDINGS

  • N. A. Radziminovich,
  • G. Bayar,
  • A. I. Miroshnichenko,
  • S. Demberel,
  • M. Ulziibat,
  • D. Ganzorig,
  • A. V. Lukhnev

DOI
https://doi.org/10.5800/GT-2016-7-1-0195
Journal volume & issue
Vol. 7, no. 1
pp. 23 – 38

Abstract

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We have compiled and analyzed earthquake focal solutions for the territory of Mongolia and its surroundings in order to reveal a spatial variability of stress orientation and stress regimes of the crust. According to the stress inversion results, the SHmax is turning from W-E in the eastern Mongolia to SW-NE in the Gobi Altay and the central Mongolia, and then to S-N in the western part of the region. Comparison with data derived from GPS measurements shows that directions of the strain axes revealed by the geodetic and seismological observations are generally consistent. A contradiction is found for the Bolnai zone where results of GPS estimation indicate the predominance of extension (in the SE-NW direction), whereas earthquake data for the longer period of seismic observations reveal compression. Compression in this zone is mainly due to the Tsetserleg-Bolnai earthquakes contribution; however, a part of the recent data on focal mechanisms fits an extensional stress field with the NNW orientated extension axis. These data are in accordance with some published works which suggest a transtensive field from some structural geology studies in the eastern part of the Bolnai zone.The paper is supplemented with a list of M≥4.5 earthquake fault plane solutions and unpublished focal mechanisms for some M≤4.5 earthquakes of the northern Mongolia and the southern Baikal region.

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