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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References
Ammon CJ, Randall GE, Zandt G (1990) On the nonuniqueness of receiver function inversions. J Geophys Res 95:15303–15318
Bendick R, McClusky S, Bilham R, Asfaw L, Klemperer S (2006) Distributed Nubia–Somalia relative motion and dike intrusion in the main Ethiopian rift. Geophys J Int 165:303–310
Boven A, Pasteels P, Punzalan LE, Yamba TK, Musisi JH (1998) Quaternary perpotassic magmatism in Uganda (Toro-Ankole Volcanic Province): age assessment and significance for magmatic evolution along the East African Rift. J Afr Earth Sci 26:463–476
Bram K (1975) Zum Aufbau der Kruste und des oberen Mantels im Bereich des westlichen Grabens des ostafrikanischen Grabensystems und im östlichen Zaire-Becken. Geophys Abh Inst Geophys Berlin, H 4
Calais E, Ebinger C, Hartnady C, Nocquet J (2006) Kinematics of the East African rift from GPS and earthquake slip vector data. In: Yirgu G, Ebinger CJ, Maguire PKH (eds) The Afar Volcanic Province within the East African Rift System, Geol Soc Spec Publ 259:177–195
Chorowicz J (2005) The East African Rift System. J Afr Earth Sci 43:379–410
Dugda MT, Nyblade AA, Julia J, Langston AC, Ammon CJ, Simiyu S (2005) Crustal structure in Ethiopia and Kenya from receiver function analysis: implications for rift development in eastern Afr J Geophys Res 110:B01303. doi:10.1029/2004JB003065
Ebinger CJ, Bechtel TD, Forsyth DW, Brown CO (1989) Effective elastic plate thickness beneath the East African and Afar plateaus and dynamic compensation of the uplifts. J Geophys Res 94:2883–2901
Huerta AD, Nyblade AA, Reusch AM (2009) Mantle transition zone structure beneath Kenya and Tanzania: more evidence for a deep-seated thermal upwelling in the mantle. Geophys J Int 177:1249–1255
Kampunzu AB, Bonhomme MG, Kanika M (1998) Geochronology of volcanic rocks and evolution of the Cenozoic Western Branch of the East African Rift System. J. Afr Earth Sci 26:441–461
Karner GD, Bymungu BR, Ebinger CJ, Kampunzu AB, Mukasa RK, Nyakaana J, Rubondo ENT, Upcott NM (2000) Distribution of crustal extension and regional basin architecture of the Albertine rift system, East Africa. Mar Petrol Geol 17:1131–1150
Kennett BLN, Engdahl ER (1991) Traveltimes for global earthquake location and phase identification. Geophys J Int 105:429–465
Klerkx J, Theunissen K, Delvaux D (1998) Persistent fault controlled basin formation since the Proterozoic along the Western Branch of the East African Rift. J Afr Earth Sci 26:347–361
Koehn D, Aanyu K, Haines S, Sachau T (2008) Rift nucleation, rift propagation and the creation of basement micro-plates within active rifts. Tectonophysics 458:105–116
Kosarev GL, Petersen SV, Vinnik LP, Roecker SW (1993) Receiver functions for the Tien Shan analog broadband network: contrasts in the evolution of structures across the Talasso-Fergana fault. J Geophys Res 98:4437–4448
Lærdal T, Talbot MR (2002) Basin neotectonics of Lakes Edward and George, East Africa Rift. Palaeogeogr Palaeoclimatol Palaeoecol 187:213–232
Langston CA (1979) Structure under Mount Rainier, Washington, inferred from teleseismic body waves. J Geophys Res 84:4749–4762
Latin D, Norry M, Tarzey R (1993) Magmatism in the Gregory rift: evidence for melt generation by a plume. J Petrol 34:1007–1027
Lindenfeld M, Rümpker G, Schumann A, Wölbern I (2008) Seismicity of the Rwenzori Region, Western Uganda. Eos Trans AGU 89(53), Fall Meet Suppl, Abstract S23A-1884
Maasha N (1975) The seismicity of the Ruwenzori Region in Uganda. J Geophys Res 80:1485–1496
Macheyeki AS, Delvaux D, De Batist M, Mruma A (2008) Fault kinematics and tectonic stress in the seismically active Manyara-Dodoma Rift segment in Central Tanzania—implication for the East African Rift. J Afr Earth Sci 51:163–188
Mavonga T (2007) Some characteristics of aftershock sequences of major earthquakes from 1994 to 2002 in the Kivu province, Western Rift Valley of Africa. Tectonophysics 439:1–12
Montelli R, Nolet G, Dahlen FA, Masters G (2006) A catalogue of deep mantle plumes: new results from finite-frequency tomography. Geochem Geophys Geosyst 7:Q11007. doi:10.1029/2006GC001248
Nolet G, Mueller S (1982) A model for the deep structure of the east African rift system from simultaneous inversion of teleseismic data. Tectonophysics 84:151–178
Nyblade AA, Brazier RA (2002) Precambrian lithosphere controls on the development of the East African rift system. Geology 30:755–758
Nyblade AA, Langston CA (2002) Broadband seismic experiments probe the East African Rift. Eos Trans AGU 83:405–408
Nyblade AA, Owens TJ, Gurrola H, Ritsema J, Langston CA (2000) Seismic evidence for a deep upper mantle thermal anomaly beneath east Africa. Geology 28:599–602
Park Y, Nyblade AA (2006) P-wave tomography reveals westward dipping low velocity zone beneath the Kenya Rift. Geophys Res Lett 33:L07311. doi:10.1029/2005GL025605
Press WH, Teukolsky SA, Vetterling WT, Flannery BP (1992) Numerical recipes in FORTRAN, 2nd edn. Cambridge Univ Press, New York, 686 pp
Ritsema J, Nyblade AA, Owens TJ, Langston CA, Van Decar JC (1998) Upper mantle seismic velocity structure beneath Tanzania, east Africa: implications for the stability of cratonic lithosphere. J Geophys Res 103:21201–21213
Schön JH (1996) Physical properties of rocks: fundamentals and principles of petrophysics. Elsevier Science Ltd., Oxford
Sebai A, Stutzmann E, Montagner J-P, Sicilia D, Beucler E (2006) Anisotropic structure of the African upper mantle from Rayleigh and Love wave tomography. Phys Earth Planet Inter 155:48–62
Stammler K (1993) SeismicHandler—programmable multichannel data handler for interactive and automatic processing of seismological analysis. Comp Geosci 19:135–140
Twesigomwe EM (1997) Seismic hazards in Uganda. J Afr Earth Sci 24:183–195
Wallner H, Schmeling H (2010) Rift induced delamination of mantle lithosphere and crustal uplift: a new mechanism for explaining Rwenzori Mountain’s extreme elevation? Int J Earth Sci. doi:10.1007/s00531-010-0521-6
Wessel P, Smith WHF (1998) New, improved version of generic mapping tools released. EOS Trans Am Geophys Union 79:579
Wölbern I, Heit B, Yuan X, Asch G, Kind R, Viramonte J, Tawackoli S, Wilke H (2009) Receiver function images from the Moho and the slab beneath the Altiplano and Puna plateaus in the Central Andes. Geophys J Int 177:296–308
Woldetinsae G, Götze HJ (2005) Gravity field and isostatic state of Ethiopia and adjacent areas. J. Afr Earth Sci 41:103–117
Yuan X, Ni J, Kind R, Mechie J, Sandvol E (1997) Lithospheric and upper mantle structure of southern Tibet from a seismological passive source experiment. J Geophys Res 102:27491–27500
Zhu L, Kanamori H (2000) Moho depth variation in southern California from teleseismic receiver functions. J Geophys Res 105:2969–2980
Acknowledgments
This research has been financed by Deutsche Forschungsgemeinschaft (DFG) within the framework of the RiftLink research group (FOR 703). We would like to thank the Geophysical Instrument Pool Potsdam (GIPP) of the GeoForschungsZentrum for providing seismic stations and W. Hanka and staff from the GEOFON data center for archiving the data. The support of the Ugandan National Council for Science and Technology and of the Ugandan Wildlife Authority is greatly appreciated. We thank Kitam Ali and Arthur Batte for help with the setup and servicing of seismic stations. Additional data from station MBAR was provided by the GSN-IRIS/IDA. We used the SeismicHandler software package (Stammler 1993) for data processing. The figures were generated using GMT software (Wessel and Smith 1998). We appreciate the detailed comments and suggestions of the two reviewers, James Hammond and Joachim R. R. Ritter, which helped to significantly improve the manuscript.
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Wölbern, I., Rümpker, G., Schumann, A. et al. Crustal thinning beneath the Rwenzori region, Albertine rift, Uganda, from receiver-function analysis. Int J Earth Sci (Geol Rundsch) 99, 1545–1557 (2010). https://doi.org/10.1007/s00531-009-0509-2
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DOI: https://doi.org/10.1007/s00531-009-0509-2