Measurement of interseismic strain accumulation across the North AnatolianFault by satellite radar interferometry

In recent years, interseismic crustal velocities and strains have been dete rmined for a number of tectonically active areas through repeated measureme nts using the Global Positioning System. The terrain in such areas is often remote and difficult. and the density of GPS measurements relatively spars e. In principle, satellite radar interferometry can be used to make millime tric-precision measurements of surface displacement over large surface area s. In practice, the small crustal deformation signal is dominated over shor t time intervals by errors due to atmospheric, topographic and orbital effe cts. Here we show that these effects can be overcome by stacking multiple i nterferograms, after screening for atmospheric anomalies, effectively creat ing a new interferogram that covers a longer time interval. In this way, we have isolated a 70 km wide region of crustal deformation across the easter n end of the North Anatolian Fault, Turkey. The distribution of deformation is consistent with slip of 17-32 mm/yr below 5-33 km on the extension of t he surface fault at depth. If the GPS determined slip rate of 24 +/-1 mm/yr is accepted, the locking depth is constrained to 18 +/-6 km.