The gravity data gathered in and around the Simav Graben in Western Anatolia were reprocessed and reinterpreted by using the standard deviation fi lter and the Euler deconvolution. The joint evaluation of results from the interpretation of gravity data and seismological studies indicates the presence of new intrusive structures in the vicinity of Simav. The intrusion is located in the eastern margin of the graben and has a thickness of 12-15 km at 2.5-3 km depth below the surface. Numerous earthquakes recorded in the eastern part of the graben are associated with this intrusion. Besides, the multidimensional modelling study of the gravity data allowed us to display the Simav Graben, the fold of the Simav Fault, the intrusion named as Naşa, and the epicenters of earthquake within the same tectonic frame. All tectonic structures were marked on the three dimensional relief model.