HR: 0800h
AN: T21B-0583    [Abstracts]
TI: Crustal response to the formation of the Hálslón reservoir in Iceland.
AU: * Ofeigsson, B G
EM: bgo@raunvis.hi.is
AF: Institute of Earth Sciences, University of Iceland, Sturlugata 7, Reykjavík, 101, Iceland
AU: Einarsson, P
EM: palli@hi.is
AF: Institute of Earth Sciences, University of Iceland, Sturlugata 7, Reykjavík, 101, Iceland
AU: Sigmundsson, F
EM: fs@hi.is
AF: Institute of Earth Sciences, University of Iceland, Sturlugata 7, Reykjavík, 101, Iceland
AU: Sturkell, E
EM: sturkell@hi.is
AF: Institute of Earth Sciences, University of Iceland, Sturlugata 7, Reykjavík, 101, Iceland
AU: Ólafsson, H
EM: hallo@hi.is
AF: Institute of Earth Sciences, University of Iceland, Sturlugata 7, Reykjavík, 101, Iceland
AU: Grapenthin, R
EM: grapenth@informatik.hu-berlin.de
AF: Geophysical Institute, University of Alaska, AK 99775, Fairbanks, AK 757320, United States
AU: Geirsson, H
EM: dori@vedur.is
AF: Icelandic Meteorological Office, Bústaðavegi 9, Reykjavík, 105, Iceland
AB: A major 2.4 km³ water reservoir (Hálslón) is being filled north of the Vatnajökull ice cap, Iceland located at the eastern edge of the plate boundary deformation zone in North Iceland. It overlies a fault system that has been active during the Holocene. When full the reservoir is 198 m deep with an area of 57 km². The filling began on September 28, 2006 and was 7 m from being full at the end of August 2007. The load that is consequently being applied on the crust gives a good opportunity to study the characteristics of the crustal response. An extensive network for crustal deformation research was established in 2005. A total of 35 benchmarks were measured in GPS-campaigns in August, 2005, 2006 and 2007. Eight continuously measuring GPS-stations where established for resolving temporal changes in the Hálslón area in near real time. The first station was established in October, 2004, three in fall 2005 and the other four in September 2006. Known crustal movements in the area prior to filling process were uplift associated with decreasing load of the nearby Vatnajökull ice cap and seasonal variations due to the annual change in snow load. Since the filling of the reservoir began in September 2006, a local deformation have been detected in the part of continuous GPS-network closest to the reservoir, including a subsidence of 10-20 mm, horizontal movements of 5-10 mm to the northwest in part of the network and movement of 5-10 mm to the south east in other parts. The time series show that the movements have not been continuous. In the first 2- 3 months of the filling the GPS-stations moved, but then ceaset until May 2007 when movements continued. This is in accordance with the increase in the water level of the reservoir. Levelling over the most prominent fault in the area near the shore of the reservoir shows that site closer to the reservoir has subsided ~1 mm Since 2005. The horizontal movements of the GPS-stations cannot be solely attributed to the direct effect of the water load. Both the movements of the GPS-sites and the levelling results across the fault suggest that a part of these movements could be due to opening of fractures. Model calculations using a Young's modulus of 30 GPa and a crustal thickness of 10 km give a maximum expected elastic crustal subsidence of about 0.1 m. Considering additional ductile movements total subsidence of about 0.3 m is expected. The results from the GPS-campaigns compared with model calculations will give additional constraints on the crustal characteristics in the area.
DE: 1209 Tectonic deformation (6924)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1857 Reservoirs (surface)
DE: 8118 Dynamics and mechanics of faulting (8004)
DE: 8163 Rheology and friction of fault zones (8034)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting