The distribution of earthquakes and volcanoes along the East African Rift system

Nusbaum, Robert L.; Girdler, R. W.; Heirtzler, J. R.; Hutt, Duncan J; Millings, Victor E; Schmoll, Bradley S; Shapiro, Joel

doi:10.18814/epiiugs/1993/v16i4/002

Cited by 9 publications

(3 citation statements)

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“…8;Iranga, 1992;Nusbaum et al, 1993). The spatial distribution of local earthquakes further indicates that, in addition to a dense earthquake swarm in the Manyara rift, a second locus of seismicity is concentrated close to the northwestern termination of the Maminzi ridge ( Fig.…”

Section: Figure 8 Distribution Of Seismicity In Tanzania Simplifiedmentioning

confidence: 87%

Neogene-Holocene rift propagation in central Tanzania: Morphostructural and aeromagnetic evidence from the Kilombero area

Gall

Gernigon

Rolet

et al. 2004

Geo. Society Am. Bull.

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Based on field studies supplemented by remote sensing and aeromagnetic data from central Tanzania, a Phanerozoic structural history for the region can be developed and placed in a broader rift context. The major contribution of this work is the recognition of rift morphology over an area lying 400 km beyond the southern termination of the Eastern, or Kenya, Rift. The most prominent rift structures occur in the Kilombero region and consist of a wide range of uplifted basement blocks fringed to the west by an east-facing half-graben that may contain 6-8 km of sedimentary strata. Physiographic features and river drainage anomalies suggest that Holocene/Neogene deformation occurs along both rift-parallel and transverse faults, in agreement with the seismogenic character of a number of oblique faults. The present-day rift pattern of the Kilombero extensional province re- †

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Section: Figure 8 Distribution Of Seismicity In Tanzania Simplifiedmentioning

confidence: 87%

Neogene-Holocene rift propagation in central Tanzania: Morphostructural and aeromagnetic evidence from the Kilombero area

Gall

Gernigon

Rolet

et al. 2004

Geo. Society Am. Bull.

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“…1). However, most of the volcanoes, which are of all ages, that are characteristic of rift formation in the Ethiopian rift are associated with the eastern branch (Baker, Mohr & Williams 1972;Maasha & Molnar 1972;Nusbaum et al 1993) and the seismic energy is released as microearthquakes (Molnar & Aggarwal 1971;Tongue, Maguire & Young 1989). Generally, the precise nature of the structural link between these rifts still remains unclear.…”

Section: Tectonic Settingmentioning

confidence: 99%

Spatial and temporal variations of seismicity in the Horn of Africa from 1960 to 1993

Ayele

Kulhánek

1997

Geophysical Journal International

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S U M M A R YSpatial and temporal variations of seismic energy release and b-value are investigated in the Horn of Africa. The results indicate that the area around the Afar Depression and southern Sudan is at a higher stress level than the southern Red Sea and Gulf of Aden. The distribution of earthquakes in the vicinity of Afar shows a systematic pattern and suggests the existence of two microplates (blocks) centred about the Danakil and Aisha horsts.

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“…The volume of igneous basalt in the eastern branch of the East African Rift system, estimated at greater than 900,000 km 3 [ Morley , 1999], far exceeds that of the western branch. Seismicity is less frequent in the eastern branch and tends to originate at shallower depths [ Fairhead and Girdler , 1971; Camelbeeck and Iranga , 1996; Nusbaum et al , 1993; Foster and Jackson , 1998]. Volcanic activity initiated about 36 Ma in the eastern branch near Lake Turkana and is dated progressively younger toward the south.…”

Section: Introductionmentioning

confidence: 99%

Evidence for an upper mantle plume beneath the Tanzanian craton from Rayleigh wave tomography

et al. 2003

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[1] The Archean Tanzanian craton, nestled between the eastern and western branches of the East African Rift, presents a unique opportunity to study the interaction of active rifting with stable cratonic lithosphere. The high density of Rayleigh wave paths recorded in a regional seismic array yields unusually precise determinations of phase velocity within the Tanzanian craton. Shear velocities in the cratonic lithosphere are higher than a global average to a depth of 150 ± 20 km. Beginning at 140 km, shear velocity decreases sharply, reaching a minimum of 4.20 ± 0.05 km/s at depths of 200-250 km. The base of the lithosphere, identified by the depth to the center of the maximum negative velocity gradient, is similar to that found beneath other Archean lithospheres. Where Cenozoic rifting crosscuts the southern corner of the craton, velocities up to 130 km depth are reduced, indicating recent disruption of the lithosphere. The anomalously low velocities beneath the Tanzanian craton indicate high temperatures and the presence of melt, consistent with the spreading of a mantle plume head beneath the craton. Tests for the possibility of a radial pattern of azimuthal anisotropy that may indicate outward flow from a plume show that a model with average anisotropy of 0.71 ± 0.17% centered SE of Lake Victoria fits the data significantly better than a uniform, single direction of anisotropy. Thus our results agree with the suggestion that an upper mantle plume, centered beneath the Tanzanian cratonic lithosphere, provides the buoyancy required for uplift of the East African Plateau.

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The distribution of earthquakes and volcanoes along the East African Rift system

Cited by 9 publications

References 0 publications

Neogene-Holocene rift propagation in central Tanzania: Morphostructural and aeromagnetic evidence from the Kilombero area

Neogene-Holocene rift propagation in central Tanzania: Morphostructural and aeromagnetic evidence from the Kilombero area

Spatial and temporal variations of seismicity in the Horn of Africa from 1960 to 1993

Evidence for an upper mantle plume beneath the Tanzanian craton from Rayleigh wave tomography

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