Active faults of the northern Central Mongolia, their correlation with neotectonics and deep structure of the region

Active tectonics of the northern Central Mongolia is studied between two largest W–E-trending left lateral fault zones – the Khangai Fault and the Tunka-Mondy zone. These strike-slip zones are parts of a single ensemble of active faults in the Mongol-Baikal region, formed under conditions of the maximum northeastern compression and the maximum northwestern extension. Between them, the ENE-trending Erzin-Agardag and Tsetserleg faults with dominant left lateral component of movements extend. A raw of the N-trending graben-shaped basins (Busiyngol, Darkhat, and Hubhugul) are situated between the eastern end of the Erzin-Agardag strike-slip fault and the western part of the Tunka-Mondy strike-slip zone. The basins form a zone of left lateral deformation, which is kinematically similar with the strike-slip faults continuing it. In contrast to the largest boundary strike-slip faults, this structural paragenesis was formed under conditions of N–S-trending relative compression and W–E-trending extension. A change in the orientation of the axes of the principal normal stress may be caused by the rotation of the block between the boundary faults. The area of graben-shaped basins is located above the uplift of the roof of a vast volume of low-velocity mantle, which we identify as the Khangai plume. Above this rise, the lithospheric mantle is reduced, and the remaining part of the lithosphere is heated and softened. The large active strike-slip faults are located above areas of lowering of the low-velocity mantle roof. Our trenching of the active faults showed that strong earthquakes repeated in the area of graben-shaped basins more often than in the large strike-slip zones, but were characterized by lower magnitudes.