HR: 15:25h
AN: G13C-08    [Abstracts]
TI: Denali Fault Earthquake Cycle Models
AU: * Freymueller, J
EM: jeff@giseis.alaska.edu
AF: Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK 99775 United States
AB: Although fault slip rates are often estimated from geodetic data such as GPS velocities, "geodetic fault slip rates" depend on the assumptions in the earthquake cycle model used. The most commonly-used model is a simple elastic half-space model with a buried dislocation, but in this model there is no accounting for the time-varying nature of deformation through the earthquake cycle, including postseismic deformation. Clearly the earth is more complicated. Pre-earthquake (1993-2002) GPS velocities are best fit by a fault slip rate of 6-8 mm/yr with a poorly constrained locking depth (Fletcher, 2002, Ph.D. thesis, University of Alaska Fairbanks). Some paleoseismic data appear consistent with the same rate but others suggest a rate as much as twice as high. Furthermore, new paleoseismic data are becoming available that constrain the earthquake history and further refine the long-term slip rate of the fault. I investigate alternative earthquake cycle models that account for postseismic relaxation following large events in an attempt to reconcile the paleoseismic and geodetic slip-rate estimates, and to determine a robust long-term slip rate for the central Denali fault. The 2002 Denali fault earthquake provides an excellent opportunity to investigate the validity of such alternative earthquake cycle models, and to better constrain model parameters. Postseismic displacements at a number of sites have exceeded 15 cm within the first two years, and the postseismic deformation is long wavelength and appears to be dominated by a deep source such as viscoelastic relaxation in the upper mantle. The postseismic response to the earlier 1964 Alaska earthquake provides further constraints on regional rheological parameters.
DE: 7221 Paleoseismology
DE: 1206 Crustal movements--interplate (8155)
DE: 1208 Crustal movements--intraplate (8110)
DE: 1236 Rheology of the lithosphere and mantle (8160)
DE: 1242 Seismic deformations (7205)
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting