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Giant, M8 earthquake-triggered ice avalanches in the eastern Kunlun Shan, northern Tibet: Characteristics, nature and dynamics

Jerome van der Woerd^,1, Lewis A. Owen^,2, Paul Tapponnier^,3, Xu Xiwei^,4, François Kervyn^,5, Robert C. Finkel^,6 and Patrick L. Barnard^,7

¹ Tectonique Active, Institut de Physique du Globe de Strasbourg EOST, 5 rue Rene Descartes, 67084 Strasbourg Cedex, France
² Department of Earth Sciences, University of California, Riverside, California 92521, USA
³ Laboratoire de Tectonique, Institut de Physique du Globe de Paris, 4, Place Jussieu, 75252 Paris Cedex 05, France
⁴ China Seismological Bureau, Beijing, China
⁵ Tectonique Active, Institut de Physique du Globe de Strasbourg EOST, 5 rue Rene Descartes, 67084 Strasbourg Cedex, France
⁶ Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, California 94550, USA,
⁷ Department of Earth Sciences, University of California, Riverside, California 92521, USA

Several giant ice avalanches were initiated by slope failure from ice caps due to strong ground motion during the 14 November 2001 M_w = 7.9 Kokoxili earthquake on the Kunlun fault. Four ice avalanches were identified on the north slope of the Burhan Budai Shan several kilometers east of the Kunlun Pass, and two were identified on the south slope of the eastern Yuxi Feng, which is 50 km west of the Kunlun Pass. These ice avalanches originated from steep-sided ice caps and progressed over and past the termini of outlet valley glaciers. In the Burhan Budai Shan, the ice avalanches comprised ice and snow that reached 2–3 km down valley beyond the snouts of the contemporary glaciers. Detailed study of the largest ice avalanche (B2) shows that the initial movement over the contemporary glacier was turbulent in nature, having a velocity >35 ms^–1. Beyond the contemporary glacier, the ice avalanche was confined within steep valley walls and entrenched paraglacial fans. Before coming to rest, this ice avalanche moved as a Bingham plastic flow at a velocity of 21 ms^–1. These ice avalanches transported little rock debris, and it is thus unlikely that they are important in contributing to the landscape evolution of this region. Yet, given the appropriate geologic and climatic conditions, ice avalanching may be an important process in the landscape evolution of high mountainous terrains. The frequency of such events is unknown, but such phenomena may become more common in the future as a consequence of increased glacier and slope instability caused by human- induced climate change. Ice avalanches, therefore, likely constitute a significant geologic hazard in the near future.

Key Words: ice avalanches • earthquakes • glaciers • Kunlun Mountains • Tibet • remote sensing