Strain accumulation across the Gazikoy-Saros segment of the North Anatolian Fault inferred from Persistent Scatterer Interferometry and GPS measurements

We use a combination of Persistent Scatterer Interferometry (PSI) and GPS observations to study interseismic crustal deformation on the Gazikoy-Saros segment (Ganos fault) of the North Anatolian Fault (NAF) zone, northwestern Turkey. The data include 44 C-band radar images collected by the ERS1 and ERS2 satellites in descending orbits between 1992 and 2003 over the study area, and campaign GPS horizontal velocities from 7 stations. The resultant secular velocity field is inverted using a nonlinear minimization algorithm to estimate parameters of two interseismic deformation models: aseismic deep slip in a purely elastic earth model (elastic half-space rheology), and viscoelastic flow in an elastic-viscoelastic earth model (viscoelastic-coupling rheology). The following conclusions are drawn: (1) The fault locking depth is estimated in the range of similar to 8-17 km (95% confidence interval) regardless of the theological model. (2) The elastic half space model implies an upper bound of 20-27 mm/yr for the slip rate on the Ganos fault. (3) Models incorporating viscoelastic rheology and seismic cycle effects suggest a lower slip rate of 18-24 mm/yr, which agrees more closely with geological estimates. However, these values are slightly sensitive to the assumed earthquake recurrence interval. (4) A bootstrap analysis of deformation data yields average crust-upper mantle viscosities of 1.3 x 10(19)-3.6 x 10(20) Pa s for the Ganos area. (c) 2007 Elsevier B.V. All rights reserved.