Escape Tectonics: Early Miocene Synchronous Onset of the North and East Anatolian Transform Faults

The motion of the Anatolian microplate, driven by the Arabia-Eurasia collision, is accommodated by the North and East Anatolian Faults (NAF and EAF). While an early Miocene onset of evolution for the NAF is well constrained by geochronological ages, a Pliocene onset of the EAF was suggested on indirect geological data. Our first U-Pb and U-Th geochronological constraints for faulting along the EAF support an early Miocene (between 23.6 ± 0.97 and 20.6 ± 0.35 Ma) structural initiation of the modern plate boundary, rather than a Pliocene onset, coeval with the NAF. Along the EAF, a long-lived, episodic deformation corridor pre-conditioned the lithosphere for the localisation of the present-day plate boundary. The EAF was reactivated and slip became localized along major faults between 8.0 ± 1.9 and 5.55 ± 0.35 Ma, with fault activity continuing to the Present. These findings indicate unequivocally that the westward extrusion of Anatolia along both NAF and EAF began simultaneously in eastern and western Anatolia. Moreover, by bridging deep-time fault evolution with present-day kinematics and seismicity, we offer a quantitative time framework to evaluate when and where deformation corridors evolved to discrete plate-boundary transform faults and discuss why such maturation matters for modern seismic hazard.