HR: 0800h
AN: T51C-0687 INVITED    [Abstracts]
TI: Structure and mechanical properties of faults from InSAR observations of coseismic deformation due to the 1999 Izmit earthquake (Turkey)
AU: * Hamiel, Y
EM: yariv@gsi.gov.il
AF: Geological Survey of Israel, 30 Malkhei Israel St., Jerusalem, 95501, Israel
AU: Fialko, Y
EM: yfialko@ucsd.edu
AF: IGPP, Scripps Institution of Oceanography, UCSD, 9500 Gilman Dr., La Jolla, 92093, United States
AB: We study the structure and mechanical properties of faults in the North Anatolian Fault system by observing near- fault deformation induced by the 1999 Mw7.4 Izmit earthquake (Turkey). We use interferometeric Synthetic Aperture Radar (InSAR) and Global Positioning System (GPS) observations to analyze the coseismic surface deformation in the near field of the Izmit rupture. The overall observed coseismic deformation is consistent with deformation predicted by a dislocation model assuming a uniform elastic crust. Previous InSAR studies revealed small-scale changes in the radar range across the nearby faults of the North Anatolian fault system. We demonstrate that these anomalous range changes are consistent with an elastic response of compliant fault zones to the stress perturbation induced by the Izmit earthquake. We examine the spatial variations and mechanical properties of fault zones around the Mudurnu Valley and Iznik faults using three-dimensional finite element models. In these models, we include compliant fault zones having various geometries and elastic properties, and apply stress changes deduced from a kinematic slip model of the Izmit earthquake. The best- fitting models suggest that the inferred fault zones have a characteristic width of a few kilometers, depth in excess of 10 km, and reductions in the effective shear modulus of about a factor of 3 compared to the surrounding rocks. The characteristic width of the best-fitting fault zone models is consistent with field observations along the North Anatolian Fault system [Ambraseys, 1970]. Our results are also in agreement with InSAR observations of small- scale deformation on faults in the Eastern California Shear Zone in response to the 1992 Landers and 1999 Hector Mine earthquakes [Fialko et al., 2002; Fialko, 2004]. The inferred compliant fault zones likely represent intense damage and may be quite commonly associated with large crustal faults.
DE: 7250 Transform faults
DE: 8010 Fractures and faults
DE: 8111 Continental tectonics: strike-slip and transform
DE: 8159 Rheology: crust and lithosphere (8031)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting