HR: 0800h
AN: G21C-0666    [Abstracts]
TI: Distributed Active Deformation in Central Mongolia
AU: * Walker, R T
EM: richw@earth.ox.ac.uk
AF: Oxford University, Department of Earth Sciences, Parks Road, Oxford, OX1 3PR, United Kingdom
AU: Molor, E
EM: e_molor@yahoo.com
AF: Mongolian University of Science and Technology, Baga Toiruu, Sukhbaatar district, Ulaanbaatar, AA1 1AA, Mongolia
AU: Nissen, E
EM: ed.nissen@earth.ox.ac.uk
AF: Oxford University, Department of Earth Sciences, Parks Road, Oxford, OX1 3PR, United Kingdom
AU: Bayasgalan, A
EM: bayas@must.edu.mn
AF: Mongolian University of Science and Technology, Baga Toiruu, Sukhbaatar district, Ulaanbaatar, AA1 1AA, Mongolia
AU: Fox, M
EM: matthew.fox@hertford.oxford.ac.uk
AF: Oxford University, Department of Earth Sciences, Parks Road, Oxford, OX1 3PR, United Kingdom
AB: We identify and describe a series of east-west left-lateral strike-slip faults (named the Songino, the Hag Nuur, the Uliastay and the South Hangay fault systems) in the Hangay mountains of central Mongolia: an area that has little in the way of recorded seismicity and which is often considered as a rigid block within the India-Eurasia collision zone. Each of the strike-slip faults show indications of late Cenozoic activity in the form of aligned sequences of sag-ponds and pressure-ridges developed in alluvial deposits. Total displacements of ~ 3 km are measured on both the Songino and South Hangay fault systems. The total displacement across the Hag Nuur fault may be as much as 11 km. Cumulative offset across the Uliastay fault systems are unknown but are unlikely to be large. The ≤ 20 km of cumulative slip on the Hangay faults could be accommodated in no more than ~ 5 Ma at the present-day rate of ~ 4 mm/yr measured by GPS. Initiation of strike-slip faulting in the Hangay thus appears to postdate the Oligocene uplift of the Hangay mountains themselves, but may be synchronous with initiation of faulting in the Gobi-Altay fault systems to the south, and might indicate a regional initiation of left-lateral shear across the whole of central Mongolia at ~ 5 Ma ago. The strike-slip faults of central Mongolia constitute a previously unrecognized hazard in this part of Mongolia. Our observations show that, despite the complete absence of instrumentally recorded seismicity in the Hangay, this part of Mongolia is cut through by numerous distributed strike-slip faults that accommodate regional left-lateral shear between Siberia and China. Central Mongolia is thus an important component of the India-Eurasia collision that would be overlooked in models of the active tectonics based on the distribution of seismicity. We suggest that active faults such as those identified in the Hangay of Mongolia might exist in other, apparently aseismic, regions within continental collision zones.
DE: 6924 Interferometry (1207, 1209, 1242)
DE: 8011 Kinematics of crustal and mantle deformation
DE: 8040 Remote sensing
DE: 8107 Continental neotectonics (8002)
DE: 8108 Continental tectonics: compressional
SC: Geodesy [G]
MN: 2007 Fall Meeting