Crustal and Upper Mantle Seismic Velocity Structure in Eastern Anatolia: Results From The Eastern Turkey PASSCAL Seismic Experiment

A temporary 29 station broadband PASSCAL array was deployed in eastern Turkey from October 1999 until August 2001. The Eastern Turkey Seismic Experiment (ETSE) was designed to image the crustal and upper mantle seismic velocity structure beneath the northernmost Arabian plate and Anatolian Plateau. These images will constrain the current geodynamic models for young continent continent collision in eastern Turkey. The array consists of two V-shaped transects and ten interior stations. We have included these ten interior stations to help provide better control for both long wavelength three dimensional velocity structure and earthquake location within the Anatolian Plateau. Hypocentral locations from the first 9 months of the deployment of the array have revealed a continuation of the Eastern Anatolian Fault Zone (EAFZ) into the easternmost portion of the Anatolian Plateau. We found no evidence for sub-crustal earthquakes in eastern Anatolia. A receiver functions profile for the eight stations located along the western transect of the ETSE array demonstrates that there is no significant crustal thickening across the EAFZ. We have observed significant dipping sub-Moho structure across the EAFZ and an apparent crustal low velocity zone within the Anatolian sub-plate. Analysis of shear-wave splitting reveals that there is no large change in upper mantle azimuthal anisotropy across the Bitlis suture and EAFZ. Comparisons with measurements of Pn anisotropy indicate that the majority of the shear-wave polarization anisotropy may be located in the asthenospheric mantle. Pn travel time tomography and analysis of regional wave attenuation have imaged an apparent change in the properties of the uppermost mantle within the vicinity of the Bitlis suture and EAFZ. We have observed very low Pn velocities and very high Sn attenuation beneath the easternmost Anatolian Plateau, and much more typical upper mantle velocities and attenuation in the northern Arabian plate. >http://atlas.geo.cornell.edu/turkey/turkey.html</a>