Comment on 'A new intracontinental transcurrent structure; the Central Anatolian Fault Zone, Turkey' by A. Kocyigit and A. Beyhan

摘要

Kocyigit and Beyhan have described the Central Anatolian Fault Zone (CAFZ), as a > 700 km long active strike-slip fault zone in Turkey. If their interpretation is correct, then several major Turkish cities are vulnerable to a significant earthquake hazard which was previously unsuspected, and the existing close agreement between observed slip rates on major strike-slip faults in Turkey and predictions from global plate motion models is spurious. Whether the CAFZ is real, or based on mistaken interpretations of diverse evidence, is thus a matter of some importance. The aim of this comment is to describe difficulties which arise over the published interpretation of the CAFZ, with the aim of encouraging either a retraction or a more thorough presentation of the available evidence in support of the existence of a major active fault zone in the required position. Three main difficulties are discussed in detail. First, strands of the CAFZ have been interpreted in many localities where previous detailed studies have either found no evidence of faulting or have reported ancient faults which have been described as no longer active. Second, many other features which previous studies have explained satisfactorily are reinterpreted as consequences of active strike-slip faulting. Finally, no observational evidence is presented for the slip rate or the timing of the start of the alleged present phase of slip on the CAFZ. The suggestion that it has slipped by 24 km during this present phase of activity is inadequately documented and conflicts with other evidence.