Velocity Structure of the Upper Crust Beneath The Northern Main Ethiopian Rift
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Date
2005-06
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Addis Abeba university
Abstract
Seismic and geologic sections are of the vital importance to the various professional
bodies, institutions and industries. They give us an insight on the grounds we are literally
standing on. This study has conducted the surface imaging of the earth to a depth of 10
~--:,----'~"---."'-
km on a 92.5 km long seismic profile line. The study was conducted starting from the
northern most of the Main Ethiopian Rift to the southern most of Afar to give us results,
which are archetype to the study area.
For the generation of seismic waves explosives were detonated inside boreholes and
programmable seismic energy recorders called "Texans" were j_epl()yed on the sutface at
about one kilometer spacing.
Reduced first arrival P-waves were picked and converted to actual time prior to inversion.
The geo-seismic model was inverted by the methods of Generalized Reciprocal Method
(GRM).
Four layers at an avcrage depth of 2 km, 4.5 km, and 8.5 km were identified with
corresponding average P-wav~ velocities of2875 mis, 4000 lnlS, 5700lnlS, and 6400 mls
~,-~----- ~--::-~ ~~-"-'-'-- .-----"-'--.,
respectively. The geological section of the studied area has been identified to rest on a
clystalline basement overlain by Meta-sediments and Meta-volcanic rocks. The first layer
has been identified as Miocene-qpaternary sediments; Cenozoic volcanic flows
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Keywords
Structure of the Upper Crust