It is accepted that crustal rocks lose their magnetisation at the Curie point temperature. At this temperature, ferrimagnetic rocks become paramagnetic. The bottom of magnetised crust determined from the spectral analysis of residual magnetic anomalies is generally interpreted as the level of the Curie point isotherm. An alternative approach to interpretation of magnetic anomalies in terms of body parameters has been achieved by characteristic curves. For this study, the prism model was used and the parameters of the body were determined by curve matching. The residual between the observed and calculated anomalies is minimised by adjusting the model parameters automatically. The Curie depth points can be obtained at bottom of the prism. For that reason several prism should be used to prepare the Curie-depth map. This method was applied to the total magnetic field data of Izmir Bay and the depths of the Curie points were determined to be about 7–10 kin. These results were compared with the gravity, seismic and the calculated heat flow values of costal geothermal bore holes and a very good relationship was observed between them.
Regional Geothermal Possibility and Geological Structural Relations; Anatolian tectonics is directly responsible for existing geothermal fields in Turkey. According to the intersection hypothesis of Ercau (1988), hot regions are situated at junction points of faults or grabens which extend in NS, NNE - SSW and EW. Neogene faults trends in the Western Anatolian are generally W - E direction and there are several grabens which are bounded with E - W trending normal faults ($eng6r 1982). The area of Izmir Bay is at the conjuncture of the Midilli - Karabmun system produced by the N - S compression and the Gediz graben which is under the extensional regime (Figure 1).
