Fault morphology along a sinistral active fault near a continental triple junction: the Ilıca segment at the northern termination of the East Anatolian fault zone, Türkiye

The East Anatolian fault zone (EAFZ) is an approximately 430 km long sinistral transform fault that bounds the southwestern margin of the Anatolian microplate between Karlıova (Bingöl) and Kahramanmaraş. It constitutes part of the Karlıova triple junction (KTJ) in eastern Anatolia. Near the KTJ, the Ilıca and Karlıova segments delineate the EAFZ. The Ilıca segment, approximately 38 km long, exhibits distinct fault-related geological structures, including linear valleys, elongated ridges, saddles, sag ponds, shutter ridges, thermal springs, and travertines. Based on extensive mapping using high-resolution imagery and field investigations, the Ilıca segment has been categorized into three sections: section 1 and section 3 exhibit broader deformation zones characterized by multiple fault branches, whereas section 2 is defined by a narrower, singular fault branch aligned with the Göynük stream. Geomorphological analyses indicate that in sections 1 and 2, erosional processes predominantly overshadow tectonic forcing, whereas section 3 is primarily governed by tectonic activity. Comparison of cumulative displacement values along the Ilıca and Karlıova segments reveals that the Ilıca segment accommodates a higher slip rate than the adjacent Karlıova segment, suggesting significant slip partitioning near the KTJ. The calculated geological slip rate for the Ilıca segment is approximately 7 mm per year, slightly lower than the GNSS-derived rate of approximately 8 mm per year. This study presents evidence contradicting previous assertions that the 1971 Bingöl earthquake produced surface rupture along the Ilıca segment. Based on our mapping and reanalysis of historical records, we propose that the most recent significant surface-rupturing event affecting parts of both the Ilıca and Karlıova segments occurred during the 1866 earthquake. Both segments constitute a seismic gap near the KTJ, with the potential to generate a future seismic event of magnitude Mw ~7.0. Additionally, potential seismic interactions with the Yedisu segment of the North Anatolian fault zone, another seismic gap near the KTJ, may influence future rupture behavior in the region.