Papers by Tesfaye T Tessema
Earth Resources and Environmental Remote Sensing/GIS Applications XIV
Earth Resources and Environmental Remote Sensing/GIS Applications XIV
Journal of Geophysical Research: Solid Earth, 2020
Geodetic observations in the Turkana Depression of southern Ethiopia and northern Kenya constrain... more Geodetic observations in the Turkana Depression of southern Ethiopia and northern Kenya constrain the kinematic relay of extension from a single rift in Ethiopia to parallel rifts in Kenya and Uganda. Global Position System stations in the region record approximately 4.7 mm/year of total eastward extension, consistent with the ITRF14 Euler pole for Nubia‐Somalia angular velocity. Extension is partitioned into high strain rates on localized structures and lower strain rates in areas of elevated topography, as across the Ethiopian Plateau. Where high topography is absent, extension is relayed between the Main Ethiopian Rift and the Eastern Rift across the Turkana Depression exclusively through localized extension on and immediately east of Lake Turkana (up to 0.2 microstrain/year across Lake Turkana). The observed scaling and location of active extension in the Turkana Depression are inconsistent with mechanical models predicting distributed stretching due to either inherited lithosph...
This study is conducted to analyze the deformation pattern at a locality in the central part of A... more This study is conducted to analyze the deformation pattern at a locality in the central part of Afar, northeast of Semera town, within the triple junction that is formed by the Arabian, Nubian and Somalian diverging plates. The study area is bordered by Manda Harraro rift in the northwest and Tendaho rift in the south. The region is one of the tectonically active areas in the world, where the episode of plate movement resulted in seafloor spreading that causes the earth"s surface to deform in the form of surface cracking, sliding and faulting. Presently this dynamic process of earth"s deformation in space and time can be accurately detected by satellite space geodetic observations. This study used Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) to study earth surface deformation. InSAR data from Envisat, image mode, with track 028 ascending and track 278 descending is used to detect surface deformation over the study area. To constrain the InSAR observations, continuously recorded GPS data obtained from DASM (2007-2012) and DASA (2008-2009) are used to investigate possible surface deformation changes in the area. The three dimensional position coordinates acquired from the DASM and DASA GPS stations over their period of observations have suggested a ground surface deformation rate of 48.5+0.2mm/yr North, 39.5+0.2mm/yr East and-9.5+0.7mm/yr Up; and 27.8+0.4mm/yr North, 43.9+0.5mm/yr East and-21.8+1.4mm/yr Up for DASM and DASA GPS stations, respectively in an absolute sense. The Up component of DASM shows two characteristics, 2.8 mm/yr up to doy 150, 2008 and-25mm/yr afterwards. The DASA shows also-10mm/yr up to doy 147, 2008 and-29mm/yr afterwards. The InSAR time-series shows-44mm/yr Line of Sight (LOS) rate in both track. The correlation between the DASM GPS and track 028 is 0.75 and it has a correlation of 0.79 with track 278. Generally, the result from this investigation suggested that there is an active subsidence in the area which needs further attention.
Journal of Volcanology and Geothermal Research
Observations of ground deformation in East Africa have been fundamental for unveiling the tectoni... more Observations of ground deformation in East Africa have been fundamental for unveiling the tectonics of continental rifting, assessing the seismic and volcanic hazard to development, and identifying geothermal resources. Here we investigate the active natural and anthropogenic processes in the Tendaho Graben, Afar using Interferometric Synthetic Aperture Radar (InSAR) collected by the Envisat satellite in 2004-2010. We used the Poly-Interferometric Rate And time series Estimation (p-RATE) method to calculate displacement in satellite line-of-sight, and a least-square inversion to decompose the line-of-sight displacement into vertical and rift perpendicular components. We observe two zones of deformation: a 20 km wide circular region of subsidence located 10 km northeast of the town of Semera with a maximum displacement rate of ∼5 cm/yr; and elongated zone (50 km) of subsidence in the area of the geothermal prospect, maximum rate of ∼4 cm/yr. The temporal characteristics of subsidence varies between these zones, with an increase in subsidence rate observed in the circular region in August 2008. We used a Bayesian inversion to find the best fitting source models and compared this to locations of seismicity and other geophysical observations. The pattern of deformation is consistent with a combination of magmatic and geothermal processes, but there does not appear to be a direct link to a sequence of dyke intrusions during 2005-2010 at Manda Hararo graben ∼60 km away, but dynamic stress changes or deep crustal flow could account for the observations.
Geochemistry, Geophysics, Geosystems
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Papers by Tesfaye T Tessema