HR: 0800h
AN: T31D-0676    [Abstracts]
TI: Is Jiali Fault still an active fault in the late Pleistocene?
AU: * Chung, L
EM: r90224109@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei, 10617, Taiwan
AU: Chen, Y
EM: ygchen@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei, 10617, Taiwan
AU: Lai, K
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei, 10617, Taiwan
AU: Yin, G
AF: Institute of Geology, China Earthquake Administration, Qijiahuozi, Chaoyang District, Beijing, 100029, China
AU: Cao, Z
AF: Seismological Bureau of Tibet Autonomous Region, No. 22 Lare Rd., Lhasa, 850000, China
AB: The Karakoram-Jiali Fault Zone (KJFZ) is the most important active structure system in the Tibetan Plateau. This zone consists of two major faults (i.e., Karakoram fault and Jiali fault) and other minor faults in between. The Karakoram fault strikes NW to SE in the western Tibet, while the Jiali fault roughly EW in the eastern Tibet, According to previous study, the Jiali fault possesses rapid dextral slip rate (15-20mm/yr) and the maximum observed offset is ca. 1.5km. Above mentioned minor faults in the middle of KJFZ can be divided into two groups. One strikes N120°-130°E, such as the Beng Co fault, the Gyaring Co fault, the Lamu Co fault, and the Awong Co fault. They are all previously reported as right-lateral strike-slip faults. The other group striking N70°-80°E seems to be conjugated with the first group. In the east of Beng Co fault and Jiali Fault, there are still several lineations striking similar to Beng Co fault. They are located in 31°-32°N, en echelon in configuration, similar length, and subparallel to each other. In this study they are tentatively regarded as part of the KJFZ. In the spring of 2007, after the feature identification by satellite imagery we conducted a field investigation to western Jiali fault and other minor faults located in its immediate west. Both of our image analysis and field survey found no evidence to indicate the late Pleistocene activity of the main trace of the Jiali fault. One of the minor faults mentioned above, on the contrary, shows lots of active fault evidence, such as ~360m offset of the last glacial moraine, many abandon channels, offset streams, and shutter ridges, etc. Based on a previously published TL date, the slip rate of this minor fault is ca. 15±2 mm/yr. The recently published GPS velocities show a relatively large WNW-ESE extension in the plateau interior (~22±3 mm/yr) and the speeds increasingly toward the east. There is also no symptom across the main trace of the Jiali fault. We therefore would like to conclude that the main Jiali fault is no longer active at least since late Pleistocene, which may be attributed to that the orientation of the Jiali fault is parallel to the extension axis and no differential stress occurs across the fault. On the other hand, the minor conjugated faults, instead, play essential roles to accommodate the stress under certain tectonic system. Based on this findings, the crustal flow model may be preferred, but fault locked model still cannot be entirely ignored.
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8107 Continental neotectonics (8002)
DE: 8109 Continental tectonics: extensional (0905)
DE: 8164 Stresses: crust and lithosphere
SC: Tectonophysics [T]
MN: 2007 Fall Meeting