Geophysical Investigation of Geothermal Potential of the Gilgil Area Nakuru County, Kenya Using Gravity

Abstract

In this study, gravity survey was used to investigate the geothermal potential field in Gilgil area Nakuru County, Kenya. The ground based CG-5 Autograv gravimeter was used to accurately measure gravity at each field station. A total of 147 gravity stations were established over an area of about 68 km2 and gravity corrections done. The complete bouguer anomaly was computed and a contour map for the study area plotted using surfer 8.0 software. Qualitative interpretation of the map shows gravity highs in the study area which were interpreted as dense bodies within the subsurface. Five profiles along the gravity highs were drawn and oriented in the directions SW-NE, NW-SE and almost N-S. The regional trend of the profiles was subtracted from the observed data yielding the residual anomaly. 2D Euler deconvolution was done on the profile data and revealed subsurface faults and bodies at a depth range of 790m-4331m. Forward modelling of selected profiles using Grav 2DC software revealed presence of dense intrusive bodies on the northern and southern parts of the study area with the density contrast range of 0.25-0.28. These bodies were interpreted as intrusive dykes that have higher density than surrounding rocks. Such intrusive dykes may be geothermal heat sources.