HR: 11:05h
AN: S11H-04    [PDF]
TI: Source models for the 2003 Denali Fault Earthquakes from InSAR and GPS.
AU: * Wright, T J
EM: tim.wright@earth.ox.ac.uk
AF: Centre for the Observation and Modelling of Earthquakes and Tectonics, Department of Earth Sciences Oxford University Parks Road, Oxford, OX4 7GR United Kingdom
AU: Lu, Z
EM: lu@usgs.gov
AF: USGS, EROS Data Center, SAIC 47914, 252nd St., Sioux Falls, SD 57196 United States
AU: Wicks, C
EM: cwicks@usgs.gov
AF: USGS, Earthquake Hazards Program 345 Middlefield Road, Menlo Park, CA 94025 United States
AB: The November 3 2002, M7.9 Denali Earthquake is the largest continental strike-slip earthquake to have occurred since the development of InSAR. It was preceded by a M6.7 ``preshock" on 23 October -- the Nenana Mountain Earthquake. We have used coseismic range changes from InSAR, and displacements from GPS where available, to find source models for the earthquakes, and to investigate the relationship between the two events. To determine the coseismic surface deformation and a source model for the Nenana Mountain Earthquake, we used 6 interferograms, constructed using radar images from the Canadian Radarsat-1 and European ERS-2 satellites. Modeling the event as dislocations in an elastic half space suggests that there was nearly 0.9 m of right-lateral strike-slip motion at depth, on a near-vertical fault, but that the maximum slip in the top 4~km of crust was less than 0.2 m. We currently have just 3 coherent Radarsat-1 interferograms that contain the coseismic deformation of the 3 November 2002, Denali Earthquake and covered the western part of the rupture. However, the spatial coverage is poor for the eastern half of the rupture, where we only have one interferogram with relatively poor coherence. The Denali Earthquake began at the western end of the rupture with thrusting on the previously unidentified Susitna Glacier Fault (SGF). The combination of ascending and descending interferograms in this area enables the fault geometry at depth to be determined reliably: inversions for fault geometry suggest that the fault had an average strike of 251$^{\circ}$ and dipped 40$^{\circ}$ to the north. We also carried out a joint inversion of the InSAR data with 40 GPS displacements, provided by the University of Alaska and UC Berkeley. Initial results suggest that the maximum slip was $\sim$12~m, around 60--70~km east of the Trans-Alaska pipeline crossing. Using our model for the Nenana Mountain Earthquake, and our geometry of the Susitna Glacier Fault, we found that the Nenana Mountain Earthquake increased the Coulomb stress at the future hypocenter of the Denali Earthquake by 30--60 kPa, encouraging the subsequent failure.
DE: 0933 Remote sensing
DE: 1242 Seismic deformations (7205)
DE: 1243 Space geodetic surveys
DE: 7205 Continental crust (1242)
DE: 7215 Earthquake parameters
SC: Seismology [S]
MN: 2003 Fall Meeting