Abstract
Although the Altyn Tagh Fault (ATF) is thought to play a key role in accommodating India-Eurasian convergence, little is known about its earthquake history. Studies of this strike-slip fault are important for interpretation of the role of faulting versus distributed deformation in the accommodation of the India- Eurasia collision. In addition, the > 1200 km long fault represents one of the most important and exemplary intracontinental strike-slip faults in the world. We mapped fault trace geometry and interpreted paleoseismic trench exposures to characterize the seismogenic behavior of the ATF. We identified 2 geometric segment boundaries in a 270 km long reach of the central ATF. These boundaries define the westernmost Wuzhunxiao, the Central Pingding, and the easternmost Xorxol (also written as Suekuli or Suo erkuli) segments. In this paper, we present the results from the Camel paleoseismic site along the Xorxol Segment at 91.759°E, 38.919°N. There evidence for the last two earthquakes is clear and 14C dates from layers exposed in the excavation bracket their ages. The most recent earthquake occurred between 1456 and 1775 cal A.D. and the penultimate event was between 60 and 980 cal A.D. Combining the Camel interpretations with our published results for the central ATF, we conclude that multiple earthquakes with shorter rupture lengths (?? 50 km) rather than complete rupture of the Xorxol Segment better explain the paleoseismic data. We found 2-3 earthquakes in the last 2-3 kyr. When coupled with typical amounts of slip per event (5-10 m), the recurrence times are tentatively consistent with 1-2 cm/yr slip rates. This result favors models that consider the broader distribution of collisional deformation, rather than those with northward motion of India into Asia absorbed along a few faults bounding rigid blocks.
Highlights
IntroductionThe sinistral Altyn Tagh Fault (ATF) traverses the northern boundary of Tibet for > 1500 km and is a major structure in the India-Eurasia con-
The sinistral Altyn Tagh Fault (ATF) traverses the northern boundary of Tibet for > 1500 km and is a major structure in the India-Eurasia con-Zack Washburn, J Ramón Arrowsmith, Guillaume Dupont-Nivet, Wang Xiao Feng, Zhang Yu Qiao and Chen Zhengle 40°Altyn Tagh Fault Kunlun fault Himalayan India Frontal Tibet Thrusts 80° Red River Fault
We have identified the active traces and most Quaternary faults, but may not show all of the early Quaternary faults because we are primarily concerned with the geometry and earthquake history for the last few kyr
Summary
The sinistral Altyn Tagh Fault (ATF) traverses the northern boundary of Tibet for > 1500 km and is a major structure in the India-Eurasia con-. The 2001 Mw 7.8 Kokoxili or Central Kunlun earthquake had a 300-400 km long rupture zone and sinistral slip up to 16.3 m (Lin et al, 2002; Klinger et al, 2003) It ruptured the eastern portion of the Kunlun Fault (van der Woerd et al, 2002). Earthquake displacements, surface rupture lengths, and recurrence intervals along major strike-slip faults such as the ATF have implications for which geodynamic models better explain continental deformation and for regional earthquake sequences in continental settings. When coupled with typical amounts of slip per event (5-10 m), the recurrence times are consistent with 1-2 cm/yr slip rates
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