Determination of lithospheric structure beneath station TBZ by use of teleseismic earthquake recordings

SUMMARY Determination of Lithospheric Structure beneath Station TBZ by Use of Teleseismic Earthquake Recordings Lithosphere structure beneath the seismic station Trabzon (TBZ) is determined by the least - squared inversion of observed radial receiver functions. The data are three component broad-band digital earthquake recordings and spans the time interval from 1996 to 1998. Among them 39 events had the required level of signal to noise ratio. From three component recordings it is possible to calculate radial and tangential receiver functions. Inversion technique is applied to radial receiver functions to acquire the elastic parameters beneath the station. To the south of station crustal structure is continental and it is oceanic in the north. Because of this nature, there is a crustal thickening from north to south. Tangential receiver functions are much affected by horizontal velocity heterogenities and thus illustrate the dipping structure in case of such occurrence. P and P -to- S (Ps) converted waves in the tangential receiver functions are indicative of dipping structures when they are particularly compared to each other at varying back-azimuths. Here, tangential receiver functions show structural dipping towards approximately southwest. Inversion of radial receiver functions reveal a sudden velocity increase in the first 10 km depth. A low velocity zone of 3.5 km/sec. occurs at depths of 20 - 35 km. Anisotropic wave propagation is present under this station and this is indicated in tangential receiver functions. Key Words: Receiver Function, Broad-band, Teleseismic, Inversion, P to S Conversion, Anizotropic.