Deformation Analysis At The Northeastern Part Of Semera Town Centeral Afar Using Insar And Gps

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.rnThis 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.rnThe 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.rnKeywords: Deformation, InSAR, GPS, LOS

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