HR: 15:25h
AN: T22C-08    [PDF]
TI: Northeastwards decrease in the late Pleistocene-Holocene slip-rate and propagation of the Altyn Tagh fault (China).
AU: * Meriaux, A
EM: meriaux1@llnl.gov
AF: IGPP, Lawrence Livermore National Laboratory, PO BOX 808, L-206, Livermore, Ca 94550` United States
AU: Ryerson, F J
EM: ryerson1@llnl.gov
AF: IGPP, Lawrence Livermore National Laboratory, PO BOX 808, L-206, Livermore, Ca 94550` United States
AU: Tapponnier, P
EM: tappon@ipgp.jussieu.fr
AF: Tectonique, IGPP, 4 place Jussieu, Paris Cedex, 75252 France
AU: Van der Woerd, J
EM: Jerome.Vanderwoerd@eost.u-strasbg.fr
AF: IPGS-EOST, 5 Rue rene Descartes, Strasbourg, 67084 France
AU: Finkel, R C
EM: finkel1@llnl.gov
AF: Seismological Bureau, 63 Fuxing Ave, Beijing, 100036 China
AU: Xu, X
AF: Seismological Bureau, 63 Fuxing Ave, Beijing, 100036 China
AU: Xu, Z
AF: Ministry of Land and Resources, Baiwanzhuand Rd, Beijing, 100037 China
AB: Measured, long-term ($>100$\,Ka) slip-rates appear to decrease northeastwards along the Altyn Tagh Fault. Our recent results imply that the rate is fastest near Tura, on the central segment of the fault ($85-89^{\circ}$E). Here, offsets of fluvial terrace risers and abandoned channels ($\approx420$\,m) and glacial features ($\approx3.5$\,km) are constrained by both radiocarbon and cosmogenic dating ($^{10}$Be and $^{26}$Al) and yield a slip rate of $\approx$30\,mm/yr. Farther East, north of Huatougou, at the transition between a push-up mountain and a pull-apart basin, cosmogenic dating of offset terrace risers on the most active trace of the fault system yields a well-constrained rate of 18\,mm/yr. Yet farther East, near Aksay, on the north Altyn Tagh fault (NATF), at three sites where extensive radiocarbon and surface exposure dating were performed, the slip-rate is $20\pm3$\,mm/yr, with a lower bound of $13\pm2$\,mm/yr. At $95^{\circ}$E, eastern of the main Subei junction, the rate found at Lou Zhao Wan on the NATF, is only on order of 15\, mm/yr with a minimum of $12.5$\,mm/yr. Finally, near Shibao Cheng ($96^{\circ}$E) the slip rate of $4\pm2$\,mm/yr has been obtained west of the junction with the Qilian Shan Front (Meyer {\it et al.}, 1996). Thus, long-term morphochronologic measurements over a length of $\approx1000$\,km indicate a systematic eastward decrease, from 30\,mm/yr to 4\,mm/yr, of the left-lateral slip-rate along the fault. This behavior is in contrast to that on the Kunlun Fault where the morphochronologic rate over a similar length of the fault appears to have remained constant over the last 45 Ka (Van der Woerd {\it et al}, 2000). At a more detailed level, the ATF slip rate appears to display a stepwise decrease at the junctions with branching, sub-perpendicular, active thrusts south of the fault. We relate this pattern to the eastward propagation of the fault, still in progress, whose present kinematics remains linked to the formation, in the last 10\,Ma, of thrusts that young to the northeast. This propagation process has been a vital element in the building of the NE corner of the Tibet plateau (Meyer {\it et al}, 1998).
DE: 8107 Continental neotectonics
DE: 8110 Continental tectonics--general (0905)
SC: Tectonophysics [T]
MN: 2003 Fall Meeting