Seismic images of crustal variations beneath the East Anatolian Plateau (Turkey) from teleseismic receiver functions

We used teleseismic P-wave receiver functions recorded by the Eastern Turkey Seismic Experiment to determine the crustal structure across an active continent-continent collision zone. Moho depth and V _p/V _s variations in the region are mapped by incorporating crustal multiples and later two-dimsional (2-D) seismic profiles are produced using a common conversion point technique with our crustal V _p/V _s estimates. Moho depths do not correlate with surface topography and reveal a relatively thin crust consistent with the high plateau being supported by hot asthenosphere near the base of the crust. Under the Arabian plate, the crust is thinnest (c. 35 km) and exhibits high V _p/V _s (≥1.8) associated with mafic compositions. In the east, the crust gradually becomes thicker towards the north and exceeds 45 km in the northeastern side whereas in the west, the crust thickens sharply near the Bitlis suture and displays pronounced Moho topography within the Anatolian plate that suggests the presence of multiple fragments. V _p/V _s variations show an anomalously high V _p/V _s corridor (≥1.85) along the North Anatolian Fault and near the youngest volcanic units (c. 3 Ma) and support the presence of partial melt. This corridor is spatially limited from both north and south by low V _p/V _s regions implying a change in crustal composition. Near the Bitlis suture, a layered V _p/V _s model points to the source of low V _p/V _s in the lower crust that may be rich in quartz. Furthermore, the seismic profiles indicate a prominent low velocity zone in the lower crust across a large area beneath the plateau that may act as a decoupling zone between the crust and upper mantle.