GEOMETRY AND KINEMATICS OF POTENTIALLY ACTIVE FAULTS IN CENTRAL MONGOLIA: IMPLICATIONS FOR THE SEISMIC SAFETY OF ULAANBAATAR
An area of 100,000 km2 in size, located between Ulaanbaatar and the four large earthquakes (M>7) was studied using state-of-the-art remote sensing techniques and geological field mapping to characterize the recent seismic activity and kinematics of previously misinterpreted and unidentified faults. Two sets of potentially active right-lateral and left-lateral faults, with similar orientations to the faults associated with the Mogod, Bulnay, Tsetserleg and Gobi-Altai earthquakes, have been identified within 200 km of Ulaanbaatar. Earthquakes generated by these nearby faults could adversely impact the many multi-story, soviet-era apartment buildings that serve as housing for the citizens of Ulaanbaatar. This investigation revealed clues of how the tectonic stress is accommodated between the historically large earthquake faults, located further to the west and southwest, and the potentially active faults located nearer to Ulaanbaatar. Besides a similar spatial orientation and kinematics of the two sets of faults, it was discovered that these faults terminate with similar fault geometries. The NW-SE striking, right-lateral strike-slip faults and E-W striking, left-lateral strike-slip faults terminate into extensional and compressional faults due to a change in strike of the faults. This observation indicates that there is a spatial and temporal relation between many of the strike-slip, extensional and compressional faults of central Mongolia.