Interseismic Slip Rate Estimations Along the North Anatolian Fault: Insights from GPS and InSAR Data

Apart from conventional geologic methods used to estimate slip rates along active faults, GPS and InSAR have become widely used geodetic techniques for constraining interseismic slip rates in active tectonic studies due to their ability to provide wider spatial coverage. The North Anatolian Fault (NAF), one of the most active transform faults in the world, continues to be a key subject of active tectonic research in Türkiye due to its major seismic activity, which has affected millions of lives. Thus, reliable slip rate estimation is critical for understanding the geodynamics and seismic hazards of the NAF. However, geologic and geodetic slip rates available in the literature show significant differences along the NAF, highlighting the need for further investigations. In this study, the newly published GPS and InSAR velocity fields are modeled within elastic half-space to constrain slip rates along profiles cutting across NAF from Saros Bay to Varto (longitudes between 26° and 42°).

Overall, the results of this study suggest that the deviations between geologic and geodetic slip rates arise mainly from slip partitioning along the secondary segments, particularly in the multi-segmented portion of the NAF in the Marmara Region. Both GPS- and InSAR-derived slip rates show similar trends and are compatible with a locking depth of 10 kilometers, although GPS-derived slip rates tend to be slightly lower than those estimated from InSAR data. From Bolu to Erzincan, slip rates remain relatively stable, ranging from 20–24 mm/year. Along the central segments of NAF, profiles between Gerede and Kargı indicate a transpressional regime transitioning into a transtension west of Niksar, where NAF bends southeastward forming multiple splays. Further east, extension again starts to accompany the strike-slip motion near Erzincan Basin. According to our findings, right-lateral motion along the main strand of NAF drops sharply towards the east just after Erzincan Basin to 16–18 mm/yr and after Karlıova Junction to 10-11 mm/yr around the Varto Fault Zone where the regime becomes transpressional.

 

Keywords: North Anatolian Fault, GPS, InSAR, geodetic slip rate analysis.