SUMMARY
We show the results of application of Differential SAR Interferometry to the MW 7.4, August 17, 1999, Izmitearthquake, Western Turkey. The differential interferogram is obtained using an interferometric ERS2 ascendingpair with a time interval of 35 days (August 13th - September 17th). The fringe pattern clearly defines the coseismicdisplacement field extended in an area of about 100 km N-S and 120 km E-W. The analysis of the interferogramshows the right-lateral strike-slip movement on the activated section of the North Anatolian fault system. Themaximum SAR-detected displacement ranges between 117.6 cm and 134.4 cm in the proximity of Gölcük. Weinvert SAR data for uniform dislocation on a single fault plane using a Montecarlo procedure, with the aim oftesting a large set of a priori possible asperity distributions on the fault. We then use a forward modeling approachto evaluate the slip variability for the dislocation using additional constraints as surface offsets and seismicitydistribution: in this case we allow unit cells to undergo different values of slip in order to refine the initial dislocationmodel. Misfits between SAR data and modeled slant range displacements are generally low for all our models(~ 12 cm). Our results indicate that slip is concentrated in the central-western part of the fault, in the upper 10-15km, tapering to the fault tips. For the Izmit case, we note that a well constrained fault model can be obtained onlyintegrating DInSAR data with additional observations. This is mainly due to an undersampling of the displacementfield by DInSAR, caused by decorrelation and lack of image data.