InSAR velocity field across the north anatolian fault (eastern Turkey): Implications for the loading and release of interseismic strain accumulation

We use the Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) techniquewith the European Space Agency's Envisat and ERS SAR data acquired on three neighboring descending tracks (T350, T078, and T307) to map the interseismic strain accumulation along a ~225km long, NW-SE trending section of the North Anatolian Fault that ruptured during the 1939, 1942, and 1943 earthquakes in eastern Turkey. We derive a line-of-sight velocity map of the region with a high spatial resolution and accuracy which, together with the maps of earthquake surface ruptures, shed light on the style of continental deformation and the relationships between the loading and release of interseismic strain along segmented continental strike-slip faults. In contrast with the geometric complexities at the ground surface that appear to control rupture propagation of the 1939 event, modeling of the high-resolution PS-InSAR velocity field reveals a fairly linear and narrow throughgoing shear zonewith an overall 20 ± 3mm/yr slip rate above an unexpectedly shallow 7 ± 2km locking depth. Such a shallow locking depth may result from the postseismic effects following recent earthquakes or from a simplified model that assumes a uniform degree of locking with depth on the fault. A narrow throughgoing shear zone supports the thick lithospheremodel inwhich continental strike-slip faults are thought to extend as discrete shear zones through the entire crust. Fault segmentation previously reported from coseismic surface ruptures is thus likely inherited from heterogeneities in the upper crust that either preexist and/or develop during coseismic rupture propagation. The geometrical complexities that apparently persist for long periods may guide the dynamic rupture propagation surviving thousands of earthquake cycles.