HR: 09:05h
AN: T31G-05    [Abstracts]
TI: Implications of river morphology response to Dien Bien Phu fault in NW Vietnam
AU: * Lai, K
EM: d92224003@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4th, Roosevelt Rd., Taipei, 116, Taiwan
AU: Chen, Y
EM: ygchen@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4th, Roosevelt Rd., Taipei, 116, Taiwan
AU: Lam, D
EM: ddinhlam@yahoo.com
AF: Institute of Geological Sciences, Vietnamese Academy of Science and Technology, Lane 84, Chualang St., Dongda, Hanoi, ơơơ, Viet Nam
AB: In northern Vietnam, most rivers are flowing southeastward sub- or parallel to the valley of Red River and characterized by long but narrow catchments. The Dien Bien Phu fault is associated with the most seismically active zone in Vietnam and situated in the potential eastern boundary of the rotating southeastern Tibetan block. It cuts the Da River, the largest tributary of Red River in northwest Vietnam and has distorted the drainage basin resulting in complex river patterns. To assess the river morphology response to active Dien Bien Phu fault, we use 1/50,000 topographic data and ASTER images to map the precise river courses and digital elevation model data of SRTM to retrieve and analyze the river profiles. From the mapping results, the N-S striking fault results in three conspicuous north-trending river valleys coincided with the different fault segments to facilitate the measurement and reconstruction of the offsets along the fault. Further combining the longitudinal profile analysis we obtain ca. 10 km offsets by deflected river as the largest left-lateral displacement recorded along the active fault. The restored results show the downstream paleochannel of the Da River had been abandoned and becomes two small tributaries in opposite flow directions at present due to differential crustal uplift. Also the present crisscross valley at the junction of the Da River and the fault is resulted from the capture by another river which has been also deflected by the neotectonics. Based on our observations on river response, the Dien Bien Phu fault is a sinistral dominant fault with an uplift occurring in its eastern block. Furthermore the active Dien Bien Phu fault does not cut through the Red River northward indicating the western block of the fault can not be regarded as a single rigid block. There should be possible to find NW-SE trending faults paralleling to Red River to accommodate the deformation of the western block of the fault.
DE: 1825 Geomorphology: fluvial (1625)
DE: 8011 Kinematics of crustal and mantle deformation
DE: 8038 Regional crustal structure
DE: 8040 Remote sensing
DE: 8107 Continental neotectonics (8002)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting