A temporary network of 50 stations was collected earthquake data for about 11 months, in the framework of a cooperative project (TÜBİTAK-NSF collaboration) between Department of Geophysical Engineering at Dokuz Eylül University and the Department of Earth and Atmospheric Sciences at Saint Louis University, to better understand crust/manto structure/anisotropy and seismic activity in Western Anatolia. Different methods were applied to this data and additional data from permanent stations in the Aegean Region. 1-D tomography application had revealed that crustal velocities are significantly lower than average continental values. The lower crustal velocities are associated with fluids at high pore pressure and high level of fractionation rather than presence of partial melt in the region. The lower crust is more homogenous than the upper crust. Seismic activity in western Anatolia is higher than previously reported. The dominant seismogenic depth for the region is about 9-10km. The results of two different receiver function analysis methods shown that Moho increases in depth by 4 to 8 km over a lateral distance of less than 100 km from the metamorphic core complexes to the upper plates, in the Aegean region. The long-lived elevated Moho under the metamorphic core complexes suggests that the lower crust in the Aegean region is at least three times stronger than that in the Basin & Range Province, where the Moho is much flatter.By using, a relative relocation algorithm, we relocated local earthquakes in the Kandilli Observatory catalog. After relocations, earthquakes are highly concentrated in three main clusters, including moderate-sized events and their aftershock activities, and reveal linear features in seismicity. Double-couple moment-tensor analysis of 72 earthquakes shown that recent N-S extension at the surface is being corresponded by dextral and sinistrial transfer faults arround the main grabens in the region. The results of shear-wave spliting measurements implied that NNW-SSE anisotropy orientation is consistent with the direction of major vertical shear plain or the resistance corresponding W-E/SW-NE compressional acceleration in the region. This resistance works as being major shear zone between small rigit bloks rather than pure N-S or NNE-SSWextension at surface. Present-day active mechanism in the depth has revealed that the region is under the influence of a couple of shear-zone trigerred by compression. Lateral NNW/NW and NNE/NE directed strike-slip faults having dominant sinistral and dextral compenent at the surface are supporting this result.