INVESTIGATION OF MAGNETIC ANOMALIES IN CAFERBEYLI GEOTHERMAL AREA (MANISA/TÜRKIYE) USING 3-D INVERSION AND RADIAL AMPLITUDE POWER SPECTRUM METHODS

The demand forgeothermal energy is increasing due to its clean, sustainable use as arenewable resource. Geothermal energy may be used in many ways, such as in hot springs and spas, geothermal powerplants, fishing and farming industry, and heating individual buildings and aswell as the entire district. Geothermal energy is the accumulation of heatenergy as hot water within hot and dry rocks, steam or gases under pressurewithin the earth's crust at various depths. The change in physical properties ofrock with temperature may be determined using electrical, electromagnetic,gravity, magnetic, seismic, radiometric, well-logging and down hole geophysicalmethods. The Caferbeyli geothermal system is situated within the confines ofthe county of Manisa about 100 km east of İzmir. Increasing demand on thermal water requiresexploring new fields. For this purpose, geophysical studies may assist inquantifying the geothermal energy potential of the area by delineatingsubsurface fractures. The major purpose of this magnetic survey is to locate theboudaries of active hydrothermal system in the South of Gediz Graben in Caferbeyli.The presence of the hydrothermal system had already been inferred from surfaceevidence of hydrothermalactivity and drillings. Firstly, 3-D prismatic models were theoreticallyinvestigated and edge detection methods were utilized to define the boundaries and the parameters of thestructure. In thefirst step of the application, it was necessary to convert the total fieldanomaly into a reduced-to-pole anomaly map. Then the geometric boudaries of the structures weredetermined by applying a MATLAB based software with 3 different edge detection algorithms, such as tilt angle,theta map and analytic signal methods. The exact location of the structureswere obtained by usingthese boundary coordinates as initial geometric parameters in theinversion process. In addition to these methods, reduction to pole and horizontal gradientmethods were applied to the data to achieve more information about the location and shape ofthe possible reservoir. As a result, the edge detection methods were found tobe successful, both inthe field and as theoretical data sets for delineating the boundaries of thepossible geothermal reservoir structure. The depth of the geothermal reservoir was determined as 2,4km from 3-D inversion and 2,32 km from radial amplitude power spectrummethods.