The Crustal Structure of Eastern Turkey from Receiver Function Inversion

The crustal structure of Eastern Turkey has been analyzed using receiver functions obtained from the teleseismic recording of the V-shaped array of 29 broadband PASSCAL stations [Eastern Turkey Seismic Experiment] deployed by the cooperation of Bogazici University, Kandilli Observatory in Turkey and Cornell University in US. The three component recordings of teleseismic events from a wide range of epicentral distances (25§-90§) were used to obtain single-event receiver functions.

In this study we analyzed the receiver functions by modeling with a grid search algorithm in order to obtain S-wave velocity structure as well as the profiling of the single-event receiver function along the western and eastern transects of the array. The stacking of single-event receiver functions was used to reduce signal generated noise and scattered energy in order to control the effects of lateral structural changes. The stacked receiver functions were modeled by performing a 6-plane layered grid-search scheme in order to model the first-order features in the receiver functions with a minimum degree of trade-off. We found no significant crustal root beneath the western portion of the array, but there is some evidence of crustal thickening in the north. The crust thickens from 44 km in the southern part of the Bitlis Suture Zone to 50 km towards the northern end of the array in the vicinity of the North Anatolian Fault. We found a low velocity zone in the crust beneath the middle part of the array where the crustal thickness is around 46-48 km. In the eastern part the array crustal thickness is increasing from the southern tip of the array where it is 40 km to the middle section of the array where the thickness reaches 48 km. The average crustal p-wave velocities are higher in the east and reach 6.25-6.40 km/s. The crustal thickness in the Arabian plate, south of the Bitlis-Zagros Suture Zone is between 38-45 km/s with the highest average velocities observed (6.40-6.60 km/s).