TITLE:
Simultaneous Modelling of Gravity and Magnetic Data in a Measured Heat Flux Area to Characterize Geothermal Heat Sources: A Case for Eburru Geothermal Complex, Kenya
AUTHORS:
Erick Rayora Nyakundi, Githiri J. Gitonga, Maurice O. K’Orowe
KEYWORDS:
Forward Modelling, Gravity Anomaly, Magnetic Anomaly, Heat Source, Heat Flux, Geothermal Gradient, Eburru
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.9 No.5,
May
26,
2021
ABSTRACT: Forward modelling of gravity and magnetic data was
done simultaneously to show the correlation between gravity and magnetic
anomalies on a measured heat flux region. The results were used to characterize
the heat source structures in Eburru area. Modelling was done using Oasis
montaj geosoft software which is an iteration process where the gravity and
magnetic anomalies were calculated and compared to the observed residual
anomaly until there was a fit. The start model was constructed based on depths
from Euler deconvolution and models constrained using stratigraphy data from
the existing wells in the study area. Forward modelling of gravity
and magnetic data revealed intrusions within the Earth’s subsurface with depth
to the top of the sources ranging from 739
m to 5811
m. The density of the sources ranges between 3.0
g/cm3 and 3.2
g/cm3 while their magnetic susceptibility was zero. This
implies that intrusions from the mantle with a magnetic susceptibility of zero
have temperatures exceeding the curie temperature of rocks. The density of the
intrusions modelled was higher than 2.67 g/cm3, the average crustal
density, hence it explains the observed positive gravity anomaly. The results also revealed that areas with high heat
flux have shallow heat sources and if the heat sources are deep, then there
must be a good heat transfer mechanism to the surface.