Investigating Ground Deformation and Possible Causative Factors in Menengai, Nakuru  

作　　者：Joline Achieng Mercy Mwaniki Joline Achieng;Mercy Mwaniki(Department of Geomatic Engineering and Geospatial Information Systems, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya)

机构地区：[1]Department of Geomatic Engineering and Geospatial Information Systems, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya

出　　处：《International Journal of Geosciences》2023年第11期1100-1122,共23页地球科学国际期刊（英文）

摘　　要：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.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.

关 键 词：DEFORMATION INSAR Menengai GEOTHERMAL FAULTING 

分 类 号：P31[天文地球—固体地球物理学]