Present-day Fault Kinematics and their Reactivation Likelihood within and South of the North Tanzania Divergence (NTD), East African Rift System: Implication for Geo-hazards Assessment
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Department of Geology, College of Earth Sciences, The University of Dodoma, P. O. Box 11090, Dodoma
Athanas Simon Macheyeki
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This study investigates the relationship between the North Tanzania Divergence (NTD), the southern part of the NTD and the rift structures in the eastern part of the East African Rift System (EARS). It also assesses the susceptibility of these structures to reactivation under the current stress field. Fault slip data and focal mechanisms from various sources have been used to determine the minimum horizontal stress axes (Shmin) of different faults, including the Eyasi rift border fault south of the NTD.
The analysis reveals that faults trending NW-SE to NNW-SSE have a sinistral sense of movement, while those trending NE-SW generally have a dextral sense of movement. The N60°E trending faults that dip easterly are not optimally oriented with the current stress field and have a low to moderate likelihood of reactivation. This includes the NE-SW trending Eyasi rift border fault (part of the NTD) and other structures oriented N60°E south of the NTD, with a computed slip tendency (Ts) of less than 0.5. Faults trending N-S, NNW-SSE, and NNE-SSW, on the other hand, have a high to the highest likelihood of reactivation (Ts > 0.85). The other faults in the study area, which trend NE-SW or NW-SE, have Ts values expressed as 0.5 ≤ Ts < 0.85.
These findings have important implications for earthquake risk assessment in the NTD and south of the NTD, as geological constraints need to be taken into account for better management and mitigation. The results could be applied elsewhere in the EARS provided that they are under E-W extensional stress regime.
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Angelier, J, (1979a) Néotectonique de l’arc égéen. Soc. Géol. Nord. Publ., v.3, 418p.
Angelier, J. (1989) From orientation to magnitudes in paleostress determinations using fault slip data. Jour. Struct. Geol., v.11, pp.37-50.
Angelier, J. (1994) Fault slip analysis and paleostress reconstruction. In: Hancock, P.L. (Ed.), Continental Deformation. Pergamon: Oxford.
Baer, G. and Hamil, Y. (2010) East African Rifting Events Revealed by InSAR 2007 Gelai, Tanzania and 2009 Karonga, Malawi. Presentation made at the Geological Survey of Malawi.
Calais, E., d’Oreye, N., Albaric, J., Deschamps, A., Delvaux, D., Déverchere, J., Ebinger, C., Ferdinand, R.W., Kervyn, F., Macheyeki A.S., Oyen, A., Perrot, J., Saria, E., Smets, B., Stamps, D.S. and Wauthier, C., (2008) Strain accommodation by slow slip and dyking in a youthful continental rift, East Africa. Nature, v.456, pp.783–787. doi:10.1038/nature07478.
Dawson, J.B. (1992) Neogene tectonics and volcanicity in the North Tanzania sector of the Gregory Rift Valley: contrasts with the Kenya sector. Tectonophysics, v.204, pp.81–92.
Delvaux, D. (1991) The Karoo to Recent rifting in the western branch of the East-African Rift System: A bibliographical synthesis. Musee Roy. Afr. Central Tervuren (Dep. Geol. Min., Rap. Ann.) 1989-1990, pp.63-83.
Dunne, W.M. and Hancock, P.L. (1994) Paleostress analysis of small-scale brittle structures, In: Hancocock, P.L. (Ed.), Continental deformation. Pergamon: Oxford, pp.101-120.
Ebinger, C., Djomani, Y.P., Mbede, E., Foster, A. and Dawson, J.B. (1997) Rifting Archaean lithosphere: The Eyasi-Manyara-Natron rifts, East Africa. Jour. Geol. Soc., v.154(6), pp.947–960. doi:10.1144/gsjgs.154.6.09473
Le Gall, B., Gerigon, L., Rolet, J., Ebinger, C., Gloaguen, R., Nilsen, O., Dypvik, H., Deffontaines, B. and Mruma, A. (2004) Neogene-Holocene rift propagation in central Tanzania: Morphostructural and aeromagnetic evidence from the Kilombero area. Geol. Soci. Amer. Bull., v.116(3/4), pp.490-510.
Le Gall, B., Gama, R., Koptev, A., Chazot, G., Boniface, N., Loget, N., Daous, M.A., Tarits, P., Plasman, M. and Hautot, S. (2021) The anomalously-propagating South Kenya rift in the context of the North Tanzanian Divergence zone, East Africa. Tectonophysics, v.814, 228968. doi:10.1016/j.tecto.2021.228968
Holmes, A. (1952) The sequence of Precambrian orogenic belts in south and central Africa: 18th Intern. Geol. Gongr. London (1984), v.14, pp.254-269.
Macheyeki ,A.S., Delvaux, D., De Batist, M. and Mruma, A. (2008) Fault kinematics and tectonic stress in the seismically active Manyara-Dodoma rift branch in Central Tanzania – Implications for the East African Rift. Jour. Afr. Earth Sci., v.51, pp.163–188.
Macheyeki, A.S. (2008) Fault Segmentation, Paleostress and Paleoseismic Investigation in the Dodoma Area, Tanzania: Implications for Seismic Hazard Evaluation. PhD thesis. University of Ghent, Belgium, 342p.
Mariita, N.O., Keller, G.R. (2007) An integrated geophysical study of the northern Kenya rift. Jour. Afr. Earth Sci., v.48, pp.80-94.
Morley, C.K. (1999) Geoscience of Rift Systems-Evolution of East Africa. Amer. Assoc. Petrol. Geologists Studies in Geol. 44, 242.
Morris, A, Ferrill, D.A. and Henderson, D.B. (1996) Slip-tendency analysis and fault reactivation. Geology, v.24(3), pp.275–278.
Nusbaum, R.L., Girgler, R.W., Heirtzler, J.R., Hutt, D.J., Green, D., Millings, V.E., Schmoll, B.S.. and Shapiro, J. (1993) The distribution of earthquakes and volcanoes along the East African Rift System. Episodes, v.16, pp.427-432.
Nyblade, A.A. and Brazier, R.A. (2002) Precambrian lithospheric controls on the development of the East African Rift System. Geology v.30, pp.755-758.
Pinna, P., Muhongo, S., Mcharo, A., Le Goff, E., Deschamps, Y., Ralay, F., Milesi, J.P. (2004) 1:2,000,000 Geology and mineral map of Tanzania. BRGM: Orléans, France.
Philip, J.Y.N. and Mosha, D.M.S. (2012) Salt lakes of the African Rift System: A valuable research opportunity for insight into nature’s concentrated multi-electrolyte science. Tanzania Jour. Sci., v.38(3), pp.1-13.
Reiss, M.C., Muirhead, J.D., Laizer, A.S., Link, F., Kazimoto, E.O., Ebinger, C.J. and Rümpker, G. (2021). The Impact of Complex Volcanic Plumbing on the Nature of Seismicity in the Developing Magmatic Natron Rift, Tanzania. Front. Earth Sci., v.8, 609805. doi: 10.3389/feart.2020.609805
Shackleton, R.M. (1986). Precambrian collision tectonics in Africa. In: Coward, M.P. and Ries, A.C. (Eds.), Collision Tectonics. Geol. Soc. Spec. Publ., v.19, pp.329-349.
Simiyu, S.M. and Keller, G.R. (1997) An integrated analysis of lithospheric structure across the East African Plateau based on gravity anomalies and recent seismic studies. Tectonophysics, v.278, pp.191-313.
Tesha, A.L., Nyblade, A.A., Keller, G.R. and Doser, D.I. (1997) Rift localization in suture thickened crust: evidence from Bouguer gravity anomalies in northeastern Tanzanian, East Africa. In: K Fuchs R, Altherr B, Muller and C. Prodehl, (Eds.), Stress and Stress Release in the Lithosphere, Tectonophysics, v.278, pp.315-328.
Zeyen, H., Volker, F., Wehrle, V., Fuchs, K., Sobolev, S.V. (1997) Styles of Continental rifting: Crust-mantle detachment and mantle plumes. Tectonophysics, v.278, pp.329-352.
