HR: 09:30h
AN: G41A-07    [Abstracts]
TI: GPS Measurement of Neotectonic Motions in the Antarctic Interior
AU: * Willis, M J
EM: willis.146@osu.edu
AF: Byrd Polar Research Center and Department of Geological Sciences, Ohio State University, 275 Mendenhall, 125 South Oval Mall, Columbus, OH 43210 United States
AU: Wilson, T J
EM: wilson.43@osu.edu
AF: Byrd Polar Research Center and Department of Geological Sciences, Ohio State University, 275 Mendenhall, 125 South Oval Mall, Columbus, OH 43210 United States
AU: James, T
EM: tjames@Nrcan.gc.ca
AF: Geological Survey of Canada, Natural Resources Canada, Pacific Geosciences Centre, 9860 West Saanich Road, Sidney, BC V8L 4B2 Canada
AB: Campaign GPS measurements made between 1996 and 2004 are used to describe the crustal velocity field in southern Victoria Land, Antarctica. The GPS network stretches along the Transantarctic Mountains from the region of the David Glacier near $75\deg$S to the Byrd Glacier region at $81.5\deg$S and encompasses volcanic islands within the adjacent West Antarctic Rift. It is composed of 32 sites, six of which have been upgraded to run continuously. The continuous stations have been installed to separate long term secular trends in vertical motion from short period seasonal signals. The array was designed to record intraplate neotectonic motions associated with Glacial Isostatic Adjustment (GIA) and possible neotectonic motions between East and West Antarctica. There is conflicting evidence on the degree of contemporary neotectonic activity in the study area. Seismic reflection profiles document faults cutting through the sedimentary column and reaching the seafloor in the north-south trending Terror Rift in the western Ross Sea, yet seismicity has yet to be detected in this region. GIA models predict that uplift in the region will have a secular motion of between 0 and 4mm per year. This uplift will be associated with a small amount of horizontal motion. GPS records an average horizontal motion of the westernmost sites in our network of 14.4mm/yr towards $149\deg$ east. When this average motion is removed from the motion of all the network sites, to approximate an East Antarctic cratonic reference frame, a significant residual motion of coastal and offshore sites is observed. This residual motion is between 1 and 3 mm/yr towards the east-northeast, perpendicular to the trend of the Transantarctic Mountains and the Terror Rift. This motion may be accommodated by faults that occur onshore in the frontal zone of the Transantarctic Mountains and/or by faults within the Terror Rift. Reasonable models of crustal response to GIA with a laterally homogeneous Earth and the D91 ice sheet history produce horizontal motion orientations similar to the GPS measurements but are unable to reproduce the magnitude of motion. The same models predict vertical motions greater than those observed. These results suggest that GIA drives part of the observed horizontal motion but that there is also an active tectonic component.
UR: http://www.geology.ohio-state.edu/TAMDEF
DE: 9310 Antarctica
DE: 8109 Continental tectonics--extensional (0905)
DE: 8158 Plate motions--present and recent (3040)
DE: 1208 Crustal movements--intraplate (8110)
DE: 1645 Solid Earth
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting