HR: 15:10h
AN: C22A-07    [PDF]
TI: Indication of active overthrust faulting along the Holocene-Wisconsin transition in the marginal zone of Jakobshavn Isbr{\ae}
AU: * L\"uthi, M P
EM: luthi@gi.alaska.edu
AF: Versuchsanstalt fur Wasserbau, Hydrologie und Glaziologie VAW, Gloriastrasse 37-39 ETH Zentrum, Zurich, 8000 Switzerland
AU: * L\"uthi, M P
EM: luthi@gi.alaska.edu
AF: University of Alaska, Fairbanks, 903, Koyukuk Drive PO Box 757320, Fairbanks, AK 99775 United States
AU: Funk, M
EM: funk@vaw.baug.ethz.ch
AF: Versuchsanstalt fur Wasserbau, Hydrologie und Glaziologie VAW, Gloriastrasse 37-39 ETH Zentrum, Zurich, 8000 Switzerland
AU: Iken, A
AF: Versuchsanstalt fur Wasserbau, Hydrologie und Glaziologie VAW, Gloriastrasse 37-39 ETH Zentrum, Zurich, 8000 Switzerland
AB: A zone of highly irregular ice motion has been detected within the ice sheet adjacent to Jakobshavn Isbr\ae, a fast moving ice stream in West Greenland. Two tilt sensors in different boreholes and frozen into the ice show angle variations of up to $0.1^\circ$ and $0.3^\circ$ within a 1200 second interval. The amplitude of these flutter oscillations increases towards the transition from Holocene to Wisconsin ice at $682\,\mathrm{m}$ depth, $150\,\mathrm{m}$ above bedrock. All other tilt sensors above and below show low background noise. A numerical model confirms that the stress configuration is exceptional in the neighborhood of the ice stream. Stress transfer from the ice stream to the margins causes an extra forcing of the basal ice at the drill site. Several possible explanations for the observed flutter oscillations are given, the most likely being dynamic rupture events or stick-slip motion along the Holocene-Wisconsin transition. If true, this would correspond to an active overthrust fault with very high loading rates.
UR: http://gi.alaska.edu/\~{}luthi/
DE: 1827 Glaciology (1863)
DE: 8123 Dynamics, seismotectonics
DE: 8158 Plate motions--present and recent (3040)
SC: Cryosphere [C]
MN: 2003 Fall Meeting