Seismic tomograpy of Sakarya basin

Key words: 17 August 1999 Earthquake, 1-D seismic tomography, 3-D seismic tomography, crustal velocity, Sakarya Basin. The aim of this thesis is to determine 3D velocity model of Sakarya Basin and its vicinity. After 17 August 1999 Earthquake, more than 3.000 aftershocks were recorded using 14 digital seismometers that were established to provide data for the area between Sakarya and Bolu to use in ?The Prediction of Earthquakes Project? which was a co-project between General Directorate of Disaster Affairs and Potsdam University. Since some earthquakes are not recorded at each station and some are out of this area, only selected recordings are used in this study. First, a new velocity structure that represents entire study area was produced by using various velocity models in the previous studies. VELEST software which produces a simultaneously and iterative inverse solution, was used to derive velocities, compute hypocentral parameters and station corrections. Afterwards, high quality data were selected to reach correct results. And 1D velocity model of P wave that belong to study area was derived. Finally, the derived 1D velocity model was arranged to use in SIMULPS14 that produce 3D tomographic solution. In this manner, tomographic inverse solution process was completed by using real travel time and 3D profiles were derived by using TOMO2GMT. Consequently, layers that lay on between 0 and 16 kilometres in the study area could be determined well than layers that lay on under the depth of 16 kilometres, since aftershocks occurred in this distance. The derived 1D velocity model shows the study area has six different velocity layers. The structure of velocity that belongs to study area was evaluated to determine whether it is compatible with geologic and tectonic structure or not.