HR: 0830h
AN: G21B-0270    [PDF]
TI: Mechanics of Postseismic Deformation Following the 2002, Mw=7.9, Denali Fault Earthquake
AU: * B\"urgmann, R
EM: burgmann@seismo.berkeley.edu
AF: University of California, Berkeley, Dept. of Earth & Planetary Science, Berkeley, CA 94720-4767 United States
AU: Calais, E
EM: ecalais@purdue.edu
AF: Purdue University, Dept. of Earth & Atmospheric Sciences, West Lafayette, IN 47907-1397 United States
AU: Freed, A
EM: freed@purdue.edu
AF: Purdue University, Dept. of Earth & Atmospheric Sciences, West Lafayette, IN 47907-1397 United States
AU: Freymueller, J T
EM: jeff@giseis.alaska.edu
AF: University of Alaska, Fairbanks, Geophysical Institute, Fairbanks, AK 99775-7320 United States
AU: Hreinsdottir, S
EM: sigrun@giseis.alaska.edu
AF: University of Alaska, Fairbanks, Geophysical Institute, Fairbanks, AK 99775-7320 United States
AB: The occurrence of the Mw 7.9 November 3, 2002 Denali earthquake has created the opportunity to collect the surface deformation measurements needed to make significant improvements in our knowledge of the dominant deformation mechanisms in the Earth's lithosphere and the rheological parameters of the fault zone and surrounding crust and upper mantle. With the technical support of UNAVCO, we installed 16 continuous GPS sites at a wide range of distances from the rupture, including some at $>$ 150 km, in order to distinguish relaxation processes in the deep fault zone, the lower crust and upper mantle. Campaign measurements of about 50 sites are scheduled at least twice a year for the next 3 years. Horizontal postseismic displacement rates at continuous sites up to 200 km from the rupture reached 1-2 mm/day in the first month after the event. They gradually decayed to ~0.2 mm/day 8 months after the event at the sites closest to the rupture. Displacement rates measured 8 months after the event at sites that had been operating before the earthquake were still ~10 times larger than the pre-earthquake secular rates. We will present models of the early transient deformation that investigate candidate deformation mechanisms such as velocity-strengthening afterslip, poroelastic rebound, and linear versus power-law viscous flow in the lower crust and upper mantle. Preliminary inversions for the time-dependent distribution of possible afterslip on and below the rupture suggest that the source of postseismic deformation reaches deep in the lower crust and/or upper mantle. The spatial and temporal evolution of the transient deformation should provide information about which mechanism dominates the early relaxation process and constrain the range of plausible rheological parameters.
DE: 1236 Rheology of the lithosphere and mantle (8160)
DE: 1243 Space geodetic surveys
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8159 Rheology--crust and lithosphere
SC: Geodesy [G]
MN: 2003 Fall Meeting