Paleoseismogenous deformations around ulan bator according to geological and geophysical data |
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Authors: | S Demberel G Batarsuren V S Imaev A L Strom O P Smekalin A V Chipizubov N N Grib A A Syasko A V Kachaev |
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Institution: | 1.Center of Astronomy and Geophysics,Mongolian Academy of Sciences,Ulan Bator,Mongolia;2.Institute of the Earth’s Crust, Siberian Branch,Russian Academy of Sciences,Irkutsk,Russia;3.Institute of Geosphere Dynamics,Russian Academy of Sciences,Moscow,Russia;4.Institute (Branch) of Federal State Autonomous Educational Foundation for Higher Professional Education,Ammosov Northeastern Federal University,Neryungri,Russia |
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Abstract: | The Gunzhin system of NE-trending active faults is described on the basis of results of special seis-motectonic studies carried
out for the first time around Ulan Bator, Mongolia. This system crosses watershed parts of stream valley. It is named after
one of them. The total length of the fault segment traced on aerial photos is 15–20 km. In valleys of some temporary stream
flows there are considerable visible horizontal displacements attaining 20–25 m, which testify to the right lateral slip (Khundullun
River). Revealed structural parageneses of thrusts and overthrusts, divergent as a fan-shaped system to the both sides from
the axial sub-vertical shift zone, are reliably confirmed by the data of geophysical investigations. Taking into account the
known correlation relationships between seismodislocation parameters (length and maximum displacement amplitude) and earthquake
magnitudes, it is possible to suggest that the Gunzhin Fault generated two paleoearthquakes with the magnitude of about 7.0
in the Late Holocene. It means that displacements along that fault could attain the intensity of 9–10 degrees in the Ulan
Bator territory according to the MSK-64 scale. This result must be taken into account in estimation of seismic hazard in the
territory discussed. |
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