University of Twente Student Theses


Analyzing surface deformation using InSAR & other remote sensing data in the Olkaria Geothermal Field & surrounding area, Kenya

Augustin, Fitriani (2012) Analyzing surface deformation using InSAR & other remote sensing data in the Olkaria Geothermal Field & surrounding area, Kenya.

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Abstract:Surface deformation can cause many problems. The study area, located in the Olkaria Geothermal Field (OGF), and its surrounding, is situated in the central Kenya rift valley, associated with an active tectonic regime in the continental rift floor. The geothermal exploitation, the groundwater extraction and the active faults segments and volcanoes are prominent features which might lead to the surface deformation in the study area. Multitemporal Envisat ASAR data from 2003 to 2008 were used to map the ground surface displacement along the line-of-sight (LOS) direction using two InSAR approaches; two-pass differential interferogram (DinSAR) and the stacking interferogram small baseline subset (SBAS). SRTM DEM was utilized to interpret the surface active faults. ASTER VNIR FCC band 321 was used to extract the land use features along the study area. Fieldwork was carried out to validate the active surface faults and collecting secondary data on geothermal parameter. Only one pair of interferogram from the two-pass differential interferogram (DinSAR) was used to analyze the surface deformation (2007-2008), while the rest were slightly dominated by noise. SBAS technique was used to map the surface deformation rate on the study area (2003-2008). The surface deformation rate recorded at OGF is around 14 mm/year of uplifting and -13 mm/year of subsidence. The trending deformation pattern was coincidently bounding with the NE&NNE faults in the OGF, which possibly can be used to identify the geothermal source within unexplored areas. The injection wells activities and the structural behavior might contribute to the surface deformation in OGF. The relative subsidence around Lake Naivasha occurred at about -7 to -10 mm/year which was coincided with the horticulture agriculture activities. Decreasing trends on the groundwater level measurement within the agriculture areas confirmed with the subsidence pattern in the two wells (e.g., Boinnet BH1 & Boinnet BH2). Groundwater extraction possibly leads to the surface deformation around Lake Naivasha. The slow subsidence about 28 mm was detected using one interferogram pair (2007-2008) associated with the active faults in the Kenya rift floor. Slight vertical displacement recorded at about 6 mm associated with the N-S trending fault. SBAS stacking interferogram (2003-2008) detected the activity of Mt. Longonot, located in the southeast of Lake Naivasha, shows uplifting in the range of 5 to 15 mm/year. The stacking interferogram using small baseline subset (SBAS) technique is able to map multi-temporal slow rate surface deformation in the study area. However, conventional two-pass differential interferogram (DinSAR), could not be applied properly. The decorrelation effects in longer time acquisition, natural effects such as atmospheric and seasonal condition and other technical effect might contribute during SAR images selections and processing. The integrated surface deformation map with the active surface faults and other secondary dataset are able to identify the cause of deformation in the three main features activities in the study area
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Programme:Geoinformation Science and Earth Observation MSc (75014)
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