ACTIVE FAULTS IN THE BASIN OF THE SELENGA, ORKHON AND TOLA RIVERS (NORTHERN MONGOLIA)
A. V. PARFEEVETS1, V. A. SANKOV2,3, S. DEMBEREL4
1Institute of the Earth’s Crust SB RAS, 664033, Irkutsk, Lermontova str., 128, Russia
aparf@crust.irk.ru
2Institute of the Earth’s Crust SB RAS, 664033, Irkutsk, Lermontova str., 134, Russia
sankov@crust.irk.ru
3Irkutsk Scientific Center SB RAS
4Institute of Astronomy and Geophysics MAS, 210351, Ulaanbaatar, Bayanzurh duureg, Maahuur tolgoi, 5-r horoo, SHUA-iyin 7-r bair, Mongolia
demberel@iag.ac.mn
Keywords: активные разломы, кинематика, палеонапряженное состояние, Северная Монголия, active faults, cinematics, paleostress state, Northern Mongolia
Abstract
The investigation concerns with the faulting activity and strain conditions, which allows reconstructions of tectonic stress field for Northern Mongolia, comprising the Selenga, Orkhon and Tola River basins, in connection with the seismic hazard assessment of the area supposedly chosen for the construction of hydroelectric power stations. The study area is situated in the zone of dynamic influence of the eastern segment of the North Khangai strike-slip fault that splits into several branches whose distribution and distribution of stress state type depends on the location relative to major fault plane. The northeastern branch traced along the Selenga River valley is dominated by the left-lateral strike-slip and normal faults, where the extensional and transtensional, and shear tensors paragenetically related to them, were reconstructed. The southeastern sector shows the predominance of the NW right-lateral strike-slip faults, reverse faults and thrusts, and their corresponding shear, transpressional and compressional stress tensors were reconstructed. Within the southwestern sector we discovered the sublatitudinal left-lateral strike-slip faults and reverse faults, with the prevailing shear, transpressional and compressional stress tensors shown in the reconstructions. As a result, it has been found that within a 100-km radius from the power sites planned for future construction of dams on the Selenga, Orkhon and Tola rivers there are 3 to 6 faults with the evidence of the Holocene seismogenic activation. Therefore, the investigated system of faults in the area supposedly chosen for the construction of hydroelectric power stations in Northern Mongolia indicates potential seismic hazard that should be considered in their design and construction.
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