HR: 0800h
AN: T11C-1274    [Abstracts]
TI: Geomorphology of the Newly Identified Jid Strike-Slip Fault in the Altay Mountains, Western Mongolia
AU: Bayasgalan, A
EM: bayas@must.edu.mn
AF: Mongolian University of Science and Technology, School of Geology , Ulaanbaatar, 49/418 Mongolia
AU: * Walker, R T
EM: rwalker@bullard.esc.cam.ac.uk
AF: University of Cambridge, Bullard Laboratories Madingley Road, Cambridge, CB3 0EZ United Kingdom
AU: Tsolmon, G
EM: tsoomoo0711@yahoo.com
AF: Mongolian University of Science and Technology, School of Geology , Ulaanbaatar, 49/418 Mongolia
AU: Tsogtbadrakh, B
EM: tsogtbadrakh@yahoo.com
AF: Mongolian University of Science and Technology, School of Geology , Ulaanbaatar, 49/418 Mongolia
AU: Smith, L K
EM: lksmith@Princeton.edu
AF: Princeton University, Department of Geosciences, Princeton, NJ 08544 United States
AU: Sarantsetseg, P
EM: saraok7@yahoo.com
AF: Mongolian University of Science and Technology, School of Geology , Ulaanbaatar, 49/418 Mongolia
AU: Mischler, J
EM: john_mischler@augustana.edu
AF: Augustana College, Department of Geology, Rock Island, IL 61201 United States
AU: McCarthy, L
EM: l_mccarthy@coloradocollege.edu
AF: Colorado College, Department of Geology, Colorado Springs, CO 80946 United States
AU: Hazlett, R
EM: rhazlett@pomona.edu
AF: Pomona College, Department of Geology, Claremont, CA 91711 United States
AU: Carson, R
EM: carsonrj@whitman.edu
AF: Whitman College, Department of Geology, Walla Walla, WA 99362 United States
AU: Molor, E
EM: emolor@yahoo.com
AF: Mongolian University of Science and Technology, School of Geology , Ulaanbaatar, 49/418 Mongolia
AB: A right-lateral strike-slip fault (herein named the Jid fault) runs north-south for 60 km in the eastern Kharkhiraa Range of the Mongolian Altay. The Altay Mountains contain seismically active thrust and strike-slip faults that have generated numerous recorded earthquakes of magnitude $>$ 7. Identifying active structures such as the Jid fault has implications for estimates of seismic hazard and for understanding the regional tectonics. The fault shows indications of recent movements at scales ranging from drainage re-organisation at the kilometre scale, to ground deformations likely to result from movements during a single earthquake. From the scale of the ruptures and the observed length of roughly 60 km the most recent earthquake may have had a magnitude of about 7.5. In addition, numerous horizontal offsets of about 10-15 m, and vertical scarps of $<$ 5 m in the youngest alluvial deposits show the likely cumulative Holocene movement. The fault has many excellent examples of features associated with oblique-slip active faults, including stream displacements, pull-apart basins, shutter ridges, and river piracy. Along most of the Jid fault trace there is a slight vertical component of motion. The vertical component is introduced by bending along the fault and is normal in some places, and reverse in others. Parts of the fault show structural complexity at the surface with numerous parallel strands having both normal and reverse components of motion. The complexities probably form a `flower structure' in cross-section. We suspect from the geomorphology that the fault may have an overall normal conponent, which is not typical of deformation within the Altay. Assuming that the last period of alluvial fan deposition was at the last glacial maximum (approximately 10-15 ka ago), the horizontal offsets of 10-15 m would imply roughly 1 mm/yr of strike-slip motion. If the fault fails in magnitude 7.5 earthquakes with 3 m of slip in each, the average time between events will be about 3,000 years.
DE: 7223 Seismic hazard assessment and prediction
DE: 7230 Seismicity and seismotectonics
DE: 8040 Remote sensing
DE: 8102 Continental contractional orogenic belts
DE: 8107 Continental neotectonics
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting