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GEOPHYSICAL RESEARCH LETTERS, VOL. 30, NO. 24, 8043, doi:10.1029/2003GL017391, 2003

Tomographic Pn velocity and anisotropy structure beneath the Anatolian plateau (eastern Turkey) and the surrounding regions

Ali I. Al-Lazki

Institute for the Study of the Continents, Cornell University, Ithaca, NY, USA


Dogan Seber

Institute for the Study of the Continents, Cornell University, Ithaca, NY, USA


Eric Sandvol

Department of Geological Sciences, University of Missouri, Columbia, MO, USA


Niyazi Turkelli

Department of Geophysics, Kandilli Observatory and Earthquake Research Institute, Bogazici University, Istanbul, Turkey


Randa Mohamad

Syrian National Seismological Center, General Establishment of Geology and Mineral Resources, Damascus, Syria


Muawia Barazangi

Institute for the Study of the Continents, Cornell University, Ithaca, NY, USA


Abstract

We use Pn phase travel time residuals to invert for mantle lid velocity and anisotropy beneath northern Arabia-eastern Anatolia continent-continent collision zone. The primary phase data were obtained from the temporary 29-station broadband PASSCAL array of the Eastern Turkey Seismic Experiment. These data were supplemented by phase data from available stations of the Turkish National Seismic Network, the Syrian National Seismic Network, the Iranian Long Period Array, and other stations around the southern Caspian Sea. In addition, we used carefully selected catalog data from the International Seismological Centre and the National Earthquake Information Center bulletins. Our results show that low (<8 km/s) to very low (<7.8 km/s) Pn velocity zones underlie the Anatolian plateau, the Caucasus, and northwestern Iran. Such low velocities are used to infer the presence of partially molten to absent mantle lid beneath these regions. In contrast, we observed a high Pn velocity zone beneath northern Arabia directly south of the Bitlis-Zagros suture indicating the presence of a stable Arabian mantle lid. This sharp velocity contrast across the suture zone suggests that Arabia is not underthrusting beneath the Anatolian plateau and that the surface suture extends down to the uppermost mantle. Pn anisotropy orientations within a single plate (e.g. Anatolia plate) show a higher degree of lateral variation compared to Pn velocity. Areas of coherent Pn anisotropy orientations are observed to continue across major fault zones such as the EAF zone.

Received 23 March 2003; accepted 21 May 2003; published 10 September 2003.

Index Terms: 7203 Seismology: Body wave propagation; 7218 Seismology: Lithosphere and upper mantle; 8102 Tectonophysics: Continental contractional orogenic belts; 8180 Tectonophysics: Tomography.

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Citation: Al-Lazki, A. I., D. Seber, E. Sandvol, N. Turkelli, R. Mohamad, and M. Barazangi (2003), Tomographic Pn velocity and anisotropy structure beneath the Anatolian plateau (eastern Turkey) and the surrounding regions, Geophys. Res. Lett., 30(24), 8043, doi:10.1029/2003GL017391.