The crustal structure of the East Anatolian plateau (Turkey) from receiver functions

An edited version of this paper was published by the American Geophysical Union (AGU). Copyright 2003, AGU. See also: http://www.agu.org/pubs/crossref/2003.../2003GL018192.shtml; http://atlas.geo.cornell.edu/turkey/publications/Zor-et-al_2003.htmThe crustal structure of the Anatolian plateau in Eastern Turkey is investigated using receiver functions obtained from the teleseismic recordings of a 29 broadband PASSCAL temporary network, i.e., the Eastern Turkey Seismic Experiment [ETSE]. The S-wave velocity structure was estimated from the stacked receiver functions by performing a 6-plane layered grid search scheme in order to model the first order features in the receiver functions with minimum trade-off. We found no significant crustal root beneath the western portion of the network, but there is some evidence of crustal thickening in the northern portion of the network. We found an average crustal thickness of 45 km and an average crustal shear velocity of 3.7 km/s for the entire eastern Anatolian plateau. Within the Anatolian plateau we found evidence of a prominent low velocity zone where the crust thickness is approximately 46 km. These results suggests that the 2 km high topography across the Anatolian plateau is dynamically supported because most of the plateau appears to be isostatically under-compensated. Also, there appears to be a region of thin crust at the easternmost edge of the Anatolian plateau that may be a relic from the accretion of island arcs to the Eurasian plate

Investigation of crustal thickness in eastern Anatolia using gravity, magnetic and topographic data

The tectonic regime of Eastern Anatolia is determined by the Arabia-Eurasia continent-continent collision. Several dynamic models have been proposed to characterize the collision zone and its geodynamic structure. In this study, change in crustal thickness has been investigated using gravity, magnetic and topographic data of the region. In the first stage, two-dimensional low-pass filter and upward analytical continuation techniques were applied to the Bouguer gravity data of the region to investigate the behavior of the regional gravity anomalies. Next the moving window power spectrum method was used, and changes in the probable structural depths from 38 to 52 km were determined. The changes in crustal thickness where free air gravity and magnetic data have inversely correlated and the type of the anomaly resources were investigated applying the Euler deconvolution method to Bouguer gravity data. The obtained depth values are consistent with the results obtained using the power spectrum method. It was determined that the types of anomaly resources are different in the west and east of the 40 degrees E longitude. Finally, using the obtained findings from this study and seismic velocity models proposed for this region by previous studies, a probable two-dimensional crust model was constituted

Shear wave splitting in a young continent-continent collision: An example from eastern Turkey

An edited version of this paper was published by the American Geophysical Union (AGU). Copyright 2003, AGU. See also: http://www.agu.org/pubs/crossref/2003.../2003GL017390.shtml; http://atlas.geo.cornell.edu/turkey/publications/Sandvol-et-al_2003b.htmWe have determined the shear wave splitting fast polarization direction and delay time using data from the ETSE broadband experiment (Eastern Turkey Seismic Experiment), a deployment of 29 broadband seismic stations across the collision zone of the Arabian, Eurasian, and Anatolian plates. Our results show that the fast polarization directions are relatively uniform and they exhibit primarily NE-SW orientations. No abrupt changes in anisotropy directions are observed across the main tectonic units in the region: the Bitlis Suture (BS) and the North and Eastern Anatolian Fault zones. The fast polarization directions are determined to be sub-parallel to the Anatolian, Arabian, and Eurasian absolute plate velocities, except for those stations in the northeastern corner of the Anatolian Plateau. Observed delay times range from 0.7 to 2.0 seconds with an average value of 1.0 second; the largest values are within the northern Anatolian Plateau which is underlain by an exceptionally low velocity zone in the uppermost mantle. We interpret shear wave splitting as the vector difference of the Eurasian lithosphere and northeastern or southwestern directed flow of the asthenospheric mantle. Comparisons of the polarization anisotropy with measurements of Pn azimuthal anisotropy suggest vertical anisotropic layering except in those areas which are underlain by partially molten uppermost mantle

Seismogenic zones in Eastern Turkey

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