HR: 0800h
AN: T41A-1269    [Abstracts]
TI: Geometry and Kinematics of Active Faults in the Mongolian-Chinese Altai Mountains: Results From Analysis of ASTER and DISP Satellite Images
AU: * Ganev, P N
EM: pganev@whittier.edu
AF: Whittier College, 13406 Philadelphia Str., Whittier, CA 90608 United States
AU: Yin, A
EM: yin@ess.ucla.edu
AF: Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, 595 Charles Young Drive East, Los Angeles, CA 90095 United States
AB: It is well established that the Cenozoic India-Asia collision has created the Himalaya and the Tibetan plateau. However, little research has been conducted on how the collision may have controlled the geometry and kinematic evolution of Cenozoic intracontinental deformation in central Asia that lies some 2000 km north of the Indo-Asian convergent front in the Himalaya. Previous geologic investigations in the Altai region have revealed the existence of a 1200 km long, NNW-striking right-slip fault system parallel to the general strike of the Altai Range extending from Goni Altai of Russia in the north to the Mongolian-Chinese Altai in the south in central Asia. However, an important question remains on how and why the fault system was created so far into the continent from the collision front. There are two end-member possibilities: (1) the faults were created as new structures that break through old structural grains via Coulomb fracture mechanism, and (2) the faults were reactivated from existing weakness following old structure grains. In the first case, relatively high magnitude of shear stress is required in the lithosphere transmitted from the Himalaya, while in the second case relatively smaller magnitude of shear stress is needed. In order to test the competing hypotheses, we determine the geometrical and kinematic relationships between secondary contractional structures and the primary strike-slip fault system by mapping active fault traces, their offset risers, deflected drainages across the active faults, and alluvial fans using CORONA, ASTER, and LANDSAT satellite images and SRTM topographic data. Our observations along the Mongolia segment of the Altai right-slip fault system reveal the presence of several prominent echelon thrusts that are aligned at an oblique angle between 25- 40° from the main trace of the right-slip fault system. This finding supports the view that the Altai right-slip fault was created as a new structure rather than reactivating along pre-existing weakness in the Paleozoic Altai accretionary orogen. The latter would require weak faults and thus subparallel contractional structures near the main strand of the Altai strike-slip system. Our results imply that the stress in the Asian lithosphere was transmitted efficiently from the Himalayan front to central Asia and its magnitude was sufficiently large to create new fractures.
DE: 8004 Dynamics and mechanics of faulting (8118)
DE: 8010 Fractures and faults
DE: 8011 Kinematics of crustal and mantle deformation
DE: 8040 Remote sensing
SC: Tectonophysics [T]
MN: Fall Meeting 2005