Natural polarization studies at balcova geothermal field*

Abstract

AbstractContrasting resistivity, temperature, pressure, porosity and fluid migrations are the main causes of ion accumulations along the discontinuities which create coupling‐induced natural current flow which is observed as the Natural Polarization Potential (NPP) on the surface. Natural Polarization Electric Field (NPE) variations were recorded along 13 profiles about 2.5 km each in a north‐south direction. Interpretation of the coincident anomalies of the NPP and the NPE field resulted in determination of the polarization angle, polarization focal depth and the azimuths of the polarized interfaces. Considerable agreement between faults delineated by previous geological and geophysical investigations and polarization discontinuities was observed. The polarization plane was observed to be horizontal in high temperature areas but steepened gradually in relatively colder regions in the northern coastal area. From the polarization depth distribution two depression zones were observed, separated by an uplifted section elongated in a north‐south direction. The basin at the eastern side had an estimated polarization depth of 1.1 km and was limited by the Agamemnon‐2 and ‐1 faults, while the western basin had an estimated depth of 1.3 km and extended in the east‐west direction not previously reported. The eastern basin extends on the north side around the town of Inciralti, the western basin appeared to be elongated towards the town of Cesme.