HR: 11:20h
AN: G12A-05    [Abstracts]
TI: Kinematic and dynamic models of deep afterslip following the 1999 Izmit-Duzce earthquake sequence
AU: * Hearn, E H
EM: ehearn@eos.ubc.ca
AF: University of British Columbia, 6339 Stores Rd., Vancouver, BC V6T 1Z4 Canada
AU: McClusky, S
EM: simon@mit.edu
AF: Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 United States
AU: Reilinger, R
EM: reilinge@erl.mit.edu
AF: Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 United States
AB: Kinematic inversions of GPS velocity data from the first four years after the Izmit-Dzce earthquake sequence indicate that most postseismic slip has occured below two high coseismic slip patches, separated by a central coseismic slip patch that extends to a depth of at least 22 km. Integrated over four years, up to 2.5 meters of afterslip has occurred in the mid- to lower crust. Deep afterslip does not completely fill the gaps between the high coseismic slip patches, suggesting that interseismic slip in the mid-crust may occur at a significant fraction of the relative plate rate. This is consistent with localized interseismic strain around the North Anatolian Fault Zone (e.g., McClusky et al., 2000) and with earthquake-cycle models incorporating frictional fault zone rheology (Lapusta et al., 2000). By four years after the Izmit earthquake, the maximum afterslip velocity (beyond the interseismic rate) had decreased to about 30 mm/year. Most features of the deep afterslip are reproduced by dynamic finite element (FE) models of fault zone creep driven by coseismic stresses, but only if coseismic slip gradients in the mid-crust are large (that is, the high-slip patches have sharp bottom edges). The FE models assume velocity-strengthening friction in the fault zone, so we have not ruled out other rheologies that could yield nonlinearly stress-dependent slip rates. Some kinematic afterslip features cannot be explained by the dynamic FE models; for example, a patch of non-decaying afterslip (~20 mm/yr) which persists below the Yalova segment of the NAFZ. This may represent either dynamically triggered slip or a local error in the secular deformation model used to correct the postseismic velocities.
DE: 7260 Theory and modeling
DE: 8159 Rheology--crust and lithosphere
DE: 7205 Continental crust (1242)
DE: 7209 Earthquake dynamics and mechanics
DE: 1208 Crustal movements--intraplate (8110)
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting