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

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 inter pretation is correct, then several major Turkish cities are vulnerable to a significant earthquake hazard which was previously unsuspected, and the ex isting close agreement between observed slip rates on major strike-slip fau lts in Turkey and predictions from global plate motion models is spurious. Whether the CAFZ is real, or based on mistaken interpretations of diverse e vidence, 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 p resentation of the available evidence in support of the existence of a majo r active fault zone in the required position. Three main difficulties are d iscussed in detail. First. strands of the CAFZ have been interpreted in man y 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detailed studies have either found no evidence of faulting or have reported ancient faults which have been described as no longer active.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 exp lained satisfactorily are reinterpreted as consequences of active strike-sl ip faulting. Finally? no observational evidence is presented for the slip r ate 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. (C) 1999 Elsevier Science B.V. All rights reserved.