Crustal Velocity Structure of Turkey from Ambient Noise Tomography

Crustal Velocity Structure of Turkey from Ambient Noise Tomography Phase velocity (left column) and horizontal resolution maps (right column) for periods of 8, 14, 25, and 40 s. Phase velocity maps, with period labeled in the lower left, show percent variations relative to the mean phase velocity. Phase velocities are plotted for regions with horizontal resolution <=150 km, with white contour lines showing regions with resolution <=100 km. Stations (gray triangles), faults (gray lines), and paleo-sutures (red lines) are also shown. The resolution maps in the right column show path coverage (red lines) and horizontal resolution.
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In eastern Turkey, the ongoing convergence of the Arabian and African plates with Eurasia has resulted in the westward extrusion of the Anatolian plate. To better understand the current state and the tectonic history of this region, we image crust and uppermost mantle structure with ambient noise tomography. Our study area extends from longitudes of 32-44 degrees E. We use continuous data from two PASSCAL deployments, our 2006-2008 North Anatolian Fault Passive Seismic Experiment and the 1999-2001 Eastern Turkey Seismic Experiment, as well as from additional seismometers in the region. We compute daily cross-correlations of noise records between all station pairs and stack them over the entire time period for which they are available, as well as in seasonal subsets, to obtain interstation empirical Green's functions. After selecting interstation cross-correlations with high signal-to-noise ratios and measuring interstation phase velocities, we compute phase velocity maps at periods ranging from 8-40 s. At all periods, the phase velocity maps are similar for winter and summer subsets of the data, indicating that seasonal variations in noise sources do not bias our results. Across the study area, we invert the phase velocity estimates for shear velocity as a function of depth. The shear velocity model, which extends to 50 km depth, highlights tectonic features apparent at the surface: the Eastern Anatolian Volcanic Province is a prominent low-velocity anomaly whereas the Kirsehir Block has relatively fast velocities. In addition, in the southeastern part of our study area, we image a high velocity region below 20 km depth which may be the northern tip of the underthrusting Arabian plate. There are velocity jumps across the Central and East Anatolian Fault Zones. The North Anatolian Fault Zone appears as a fast anomaly in the upper crust.
</p><p>Acknowledgements: This work was fund by the National Science Foundation through grant EAR-0309838 and Independent Research and Development time.</p>

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