PRELIMINARY RESULTS OF CRUSTAL STRUCTURE AND EARTHQUAKE FOCAL MECHANISMS IN WESTERN TURKEY FROM THE 2003 SEISMIC RECORDING EXPERIMENT

Western Turkey is one of the most seismically active continental regions in the world and much of it is undergoing extensive north-south extensional deformation. In a cooperative study, seismologists from Saint Louis University and Dokuz Eylul University in Izmir, Turkey, deployed 5 broadband and 45 short-period seismic stations in western Anatolia between November 2002 and October 2003. 41 short-period stations were located along a 100-km-long NS profile in the central portion of the zone of extension (the central Menderes Massif). The remaining instruments were deployed as a regional array distributed throughout the region. We used teleseismic receiver functions to estimate crustal thicknesses and Poission's ratios beneath the stations. A 2-D crustal image beneath the linear array was obtained using CCP stacking of receiver functions. The result shows that Moho depth varies from 27 to 30 km in the study area with the shallowest part under the Kucuk Menderes Graben where large Tertiary uplift has been reported. We also determined focal mechanisms of 34 earthquakes with magnitudes larger than 3.5 in the region. All of them show either strike-slip or normal faulting with near-horizontal T-axes (extensional axes) in the NS direction.