Mapping of Crustal Thickness Variation in Southern Afar Using Gravity Survey

Dessalegn, Tekle Tiku (2009) Mapping of Crustal Thickness Variation in Southern Afar Using Gravity Survey. Masters thesis, Addis Ababa University.

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Abstract

The Afar Depression in north eastern Ethiopia is a scientific treasure trove. It is a site of a triple junction, where three plates (the Nubian plate, the Arabian plate, and the Somalian plate) are simultaneously pulling away from each other. The powerful stresses in the crust lead to frequent earth quakes and volcanism thereby producing deep cracks and fissures in the region. These tectonic activities and the sedimentation that occurs in the area change the topography, which affects the crustal thickness. Analysis of the gravity data, obtained from the Ethiopian institute of geological survey (EIGS), constrained with seismic refraction results in the study area and the Euler deconvolution results produced here, was done to study the crustal thickness variation in the southern Afar Depression including the region between 8.80 to 110N and 39.80 to 42.70E . The Bouguer gravity, which shows the depression clearly separated from the rest of the study region by relatively higher values, is dominated by a strong regional gravity while the residual anomaly indicates elongated higher (positive) gravity values that follows a trend, which over laps with crustal extension (thinning) revealed by seismic refraction survey conducted in the area. Upward continuation results also support the idea that deeper effects influence the Bouguer gravity. Higher total horizontal gradient shows faulted structures. Particularly, this high gradient bounds the depression in the west and south east, which overlaps with the escarpment faults separating the depression from the western and south eastern plateaus. Gravity modeling using seismic refraction model and Euler deconvolution result, produced here, as constraints indicate a minimum crustal thickness of about 22.7 and 23.5 under profiles BB` and CC` respectively. The modeling also shows deep seated faults particularly under profile CC.

Item Type:	Thesis (Masters)
Subjects:	G Geography. Anthropology. Recreation > G Geography (General) Q Science > Q Science (General) Q Science > QE Geology
Divisions:	Africana
Depositing User:	Selom Ghislain
Date Deposited:	27 Jun 2018 07:13
Last Modified:	27 Jun 2018 07:13
URI:	http://thesisbank.jhia.ac.ke/id/eprint/5971

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