Crustal thinning beneath the Rwenzori region, Albertine rift, Uganda, from receiver-function analysis |
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Authors: | Ingo Wölbern G Rümpker A Schumann A Muwanga |
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Institution: | 1. Institute of Geosciences, Goethe University Frankfurt, Altenh?fer Allee 1, 60438, Frankfurt am Main, Germany 2. Department of Geology, Makerere University Kampala, Kampala, Uganda
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Abstract: | The Rwenzori mountains in western Uganda, with a maximum elevation of more than 5,000 m, are located within the Albertine
rift valley. We have deployed a temporary seismic network on the Ugandan side of the mountain range to study the seismic velocity
structure of the crust and upper mantle beneath this section of the rift. We present results from a receiver-function study
revealing a simple crustal structure along the eastern rift flank with a more or less uniform crustal thickness of about 30 km.
The complexity of inner-crustal structures increases drastically within the Rwenzori block. We apply different inversion techniques
to obtain reliable results for the thickness of the crust. The observations expose a significantly thinner crust beneath the
Rwenzori range with thickness values ranging from about 20–28 km beneath northern and central parts of the mountains. Our
study therefore indicates the absence of a crustal root beneath the Rwenzori block. Beneath the Lake Edward and Lake George
basins we detect the top of a layer of significantly reduced S-wave velocity at 15 km depth. This low-velocity layer may be
attributed to the presence of partial melt beneath a region of recent volcanic activity. |
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