TITLE:
Investigating Ground Deformation and Possible Causative Factors in Menengai, Nakuru
AUTHORS:
Joline Achieng, Mercy Mwaniki
KEYWORDS:
Deformation, InSAR, Menengai, Geothermal, Faulting
JOURNAL NAME:
International Journal of Geosciences,
Vol.14 No.11,
November
24,
2023
ABSTRACT: Ground deformation measurements are important indicators of subsurface
changes which may inform potentially catastrophic events such as structural
damage to buildings or dams, derailing of rail lines, and slope failure.
Consequently, there is a need for studies to quantify these measurements
especially in areas predisposed due to these conditions. One such area is the
Menengai caldera in the East African rift where faulting, magmatism and
large-scale human activities are happening. This research investigates the
magnitude of deformation experienced in Menengai-Subukia
area and the relationship with spatial distribution of active faults and human
activities such as geothermal development and land use. Sentinel 1 images for
the duration 2015 to 2021 were processed in the Sentinel Application Platform
(SNAP) using the Terrain Observation with Progressive Scans SAR (TOPSAR)
technique. The interferograms showed that subsidence exists within Menengai
Geothermal Field (MGF). Structural mapping consisted of automatic lineament
extraction in PCI Geomatica using Sentinel 1 images to generate line density
map accompanied with Rose diagram which showed concentration and orientation of
faults. These faults are attributed to the uplift and
subsidence in Menengai caldera due to extension of the stress regime of magma
activity below the caldera. Supervised image classification was carried out on
Sentinel 2 images in ENVI to generate Land Use Land Cover maps. Validation was
done for some reference points (geothermal wells/power plants) and compared
with results from the interferograms. This was done by fitting a graphical
model of the GPS data and corresponding deformation obtained from the Sentinel
1 interferograms. The findings suggest that the most probable cause of
deformation in the area is due to geothermal activities and groundwater
abstraction. These techniques, coupled with continuous monitoring could be
useful for land-use planning and prediction of geological hazards.