Establishment of regional reference frames for quantifying active deformation areas in Anatolia

Abstract

We computed the velocity fields in various frames at 373 sites in Turkey from the GPS measurements between the years 1992 and 2004 with an unprecedented temporal and spatial resolution. Each frame realization can be considered as revealing or substantiating different geophysical phenomena; a Eurasia-fixed frame quantifying the rigid-body rotation of Central Anatolia and dextral North Anatolian mega shear zone, an Arabia-fixed frame constraining the East Anatolian thrust and sinistral shear zone, an Anatolia-fixed frame putting an upper bound to the extension of West Anatolia and the rigidity of Central Anatolia. We derived a best fitting Euler vector of Anatolia-Eurasia motion as 31.7° ± 0.1°N, 31.8° ± 0.1°E with a rotation of 1.45° ± 0.01 °/Myr using the sites in the rigid part of Anatolia. The Euler vector gives about 24 ± 1 mm/yr for an upper bound of the North Anatolian Fault System (NAFS) slip. Relative motion of Anatolia with respect to the Arabia was found to be 32.1° ± 0.3 °N, 38.5° ± 0.9°E with a rotation of 1.10° ± 0.02°/Myr implying an average slip rate of 8 ± 1 mm/yr. While the estimation of Euler parameters significantly depends on the distribution of the sites, similar velocities could be obtained using Euler parameters due to the high correlation of Euler Pole’s latitude and rotation rate. We used data with much better spatial coverage than the earlier studies and found 0.25 ± 0.01°/Myr and 0.30 ± 0.02 °/Myr larger rotation rates for Anatolia-Eurasia and Anatolia-Arabia motions, respectively. Further strain analysis reveals that the decoupling of Anatolian plate from Arabian plate along sinistral East Anatolian Fault System (EAFS) is 16 ± 1 mm/yr slower than NAFS and Central and Eastern Anatolia are characterized as being in coherent and diffused deformation respectively.