Lithospheric low-velocity zones associated with a magmatic segment of the Tanzanian Rift, East Africa

Plasman, Matthieu; Tiberi, Christel; Ebinger, C. J.; Gautier, Stéphanie; Albaric, Julie; Peyrat, S.; Déverchère, Jacques; Gall, Bernard Le; Tarits, Pascal; Roecker, S. W.; Wambura, F.; Muzuka, Alfred N. N.; Mulibo, G. D.; Mtelela, K.; Msabi, Michael; Kianji, G.; Hautot, Sophie; Perrot, Julie; Gama, Remigius

doi:10.1093/gji/ggx177

Cited by 32 publications

(71 citation statements)

References 88 publications

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“…The non-DC source mechanisms could therefore be indicative of magmatic fluids that percolate up faults during rupture, consistent with measurements of active magmatic CO 2 degassing along fissures and fault traces in the region Muirhead et al, 2016). These crack-type MTs reveal a Poisson's ratio of 0.28 which is consistent with slightly higher Vp/Vs ratios detected beneath the rift axial valley (see Text S6; Plasman et al, 2017;Roecker et al, 2017). These crack-type MTs reveal a Poisson's ratio of 0.28 which is consistent with slightly higher Vp/Vs ratios detected beneath the rift axial valley (see Text S6; Plasman et al, 2017;Roecker et al, 2017).…”

Section: Source Interpretation and Processessupporting

confidence: 82%

Insights Into Fault‐Magma Interactions in an Early‐Stage Continental Rift From Source Mechanisms and Correlated Volcano‐Tectonic Earthquakes

Oliva

Ebinger

Wauthier

et al. 2019

Geophysical Research Letters

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Strain in magmatic rifts is accommodated by both faulting and dike intrusion, but little is known of the frequency of dike intrusions in early‐stage rifts. We use a new earthquake data set from a dense temporary seismic array (2013–2014) in the ~7‐Myr‐old Magadi‐Natron‐Manyara section of the East African Rift, which includes the carbonatitic Oldoinyo Lengai volcano that erupted explosively in 2007–2008. Full moment tensor analyses were performed on M > 3.4 earthquakes (0.03‐ to 0.10‐Hz band) that occurred during the intereruptive cycle. We find two opening crack‐type and various non‐double‐couple earthquake source mechanisms and interpret these as fluid‐involved fault rupture. From waveform analysis on the nearest permanent seismic station, we conclude that similar rupture processes probably occur over eruptive and intereruptive cycles. The repeated and dynamically similar fluid‐involved seismicity, along with intrabasinal localization of active deformation, suggests that significant and persistent strain is accommodated by magmatic processes, modulated by tectonic cycles.

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Section: Source Interpretation and Processessupporting

confidence: 82%

Insights Into Fault‐Magma Interactions in an Early‐Stage Continental Rift From Source Mechanisms and Correlated Volcano‐Tectonic Earthquakes

Oliva

Ebinger

Wauthier

et al. 2019

Geophysical Research Letters

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“…Our Moho depth results are also in general agreement with Moho depth estimates obtained from broadband passive seismic receiver function analysis by Plasman et al (). Two of the passive seismic stations used by these authors to image the Moho beneath the North Tanzania Divergence are located in the southernmost part of our study area.…”

Section: Resultssupporting

confidence: 91%

“…For this site, we calculate an error of 1.42 km for the 32‐km Moho depth we obtained from the inversion of the Bouguer gravity anomalies of the EIGEN‐6C4. We find the Moho depth of 37.1 km obtained by Plasman et al () for station KEN4 to be almost identical to the Moho depth of 35 km we obtain for this site given that the error reported by these authors for this station is 1.7 km. For this site (KEN4), we calculate an error of 1.56 km for the 35‐km Moho depth we obtain from the inversion of the Bouguer gravity anomalies of the EIGEN‐6C4.…”

Section: Resultssupporting

confidence: 90%

“…Plasman et al () obtained a Moho depth of 28.0 km for station KEN2 and a Moho depth of 37.1 km for station KEN4. We find the 28.0‐km Moho depth obtained by Plasman et al () for station KEN2 to be slightly shallower than the Moho depth of 32 km we obtained for this site (Figure b). We note here that these authors reported an error of 6.8 km for the Moho depth estimated for station KEN2.…”

Section: Resultsmentioning

confidence: 96%

“…These stations are shown with red triangles labeled KEN2 and KEN4 in Figure b. Plasman et al () obtained a Moho depth of 28.0 km for station KEN2 and a Moho depth of 37.1 km for station KEN4. We find the 28.0‐km Moho depth obtained by Plasman et al () for station KEN2 to be slightly shallower than the Moho depth of 32 km we obtained for this site (Figure b).…”

Section: Resultsmentioning

confidence: 97%

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Development of Late Jurassic‐Early Paleogene and Neogene‐Quaternary Rifts Within the Turkana Depression, East Africa From Satellite Gravity Data

Emishaw

Abdelsalam

2019

Tectonics

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The Turkana Depression (TD) is a NW trending topographic corridor within the East African Rift System between the Ethiopia‐Yemen plateau in the northeast and the East African plateau to the southwest. The Anza rift within the TD is a NW‐SE trending failed arm of a late Jurassic rift‐rift‐rift triple junction. This rift is correlated with the Sudan and South Sudan rifts. The Anza rift is intersected by the East African Rift System represented by the N‐S trending Turkana rifted zone. We image the lithospheric structure beneath the TD using satellite gravity data. We also use these data to model crustal density distribution beneath the Kino Sogo fault belt, part of the Turkana rifted zone. Our results show thinner crust (23–28 km) and lithosphere (140–150 km) beneath the TD. We interpret this as due to extension that resulted in the formation of the Kenya‐Sudan and South Sudan rifts. Our results also show that crustal depth between 0 and 4.8 km is dominated by N‐S density contrast anomalies and between 4.8 and 14.5 km by E‐W anomalies. We interpret the N‐S anomalies as due to the presence of Precambrian structure that might have facilitated strain localization during the initiation of the Kino Sogo fault belt. Differently, we interpret the E‐W anomalies as due to the presence E‐W trending faults that were formed in association with the development of the Anza rift and/or Turkana rifted zone and were later filled with Mesozoic and Cenozoic mafic dikes.

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Spatially Variable CO₂ Degassing in the Main Ethiopian Rift: Implications for Magma Storage, Volatile Transport, and Rift‐Related Emissions

Hunt

Zafu

Mather

et al. 2017

Geochem Geophys Geosyst

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Deep carbon emissions from historically inactive volcanoes, hydrothermal, and tectonic structures are among the greatest unknowns in the long‐term (∼Myr) carbon cycle. Recent estimates of diffuse CO2 flux from the Eastern Rift of the East African Rift System (EARS) suggest this could equal emissions from the entire mid‐ocean ridge system. We report new CO2 surveys from the Main Ethiopian Rift (MER, northernmost EARS), and reassess the rift‐related CO2 flux. Since degassing in the MER is concentrated in discrete areas of volcanic and off‐edifice activity, characterization of such areas is important for extrapolation to a rift‐scale budget. Locations of hot springs and fumaroles along the rift show numerous geothermal areas away from volcanic edifices. With these new data, we estimate total CO2 emissions from the central and northern MER as 0.52–4.36 Mt yr−1. Our extrapolated flux from the Eastern Rift is 3.9–32.7 Mt yr−1 CO2, overlapping with lower end of the range presented in recent estimates. By scaling, we suggest that 6–18 Mt yr−1 CO2 flux can be accounted for by magmatic extension, which implies an important role for volatile‐enriched lithosphere, crustal assimilation, and/or additional magmatic intrusion to account for the upper range of flux estimates. Our results also have implications for the nature of volcanism in the MER. Many geothermal areas are found >10 km from the nearest volcanic center, suggesting ongoing hazards associated with regional volcanism.

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Lithospheric low-velocity zones associated with a magmatic segment of the Tanzanian Rift, East Africa

Cited by 32 publications

References 88 publications

Insights Into Fault‐Magma Interactions in an Early‐Stage Continental Rift From Source Mechanisms and Correlated Volcano‐Tectonic Earthquakes

Insights Into Fault‐Magma Interactions in an Early‐Stage Continental Rift From Source Mechanisms and Correlated Volcano‐Tectonic Earthquakes

Development of Late Jurassic‐Early Paleogene and Neogene‐Quaternary Rifts Within the Turkana Depression, East Africa From Satellite Gravity Data

Spatially Variable CO₂ Degassing in the Main Ethiopian Rift: Implications for Magma Storage, Volatile Transport, and Rift‐Related Emissions

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Lithospheric low-velocity zones associated with a magmatic segment of the Tanzanian Rift, East Africa

Cited by 32 publications

References 88 publications

Insights Into Fault‐Magma Interactions in an Early‐Stage Continental Rift From Source Mechanisms and Correlated Volcano‐Tectonic Earthquakes

Insights Into Fault‐Magma Interactions in an Early‐Stage Continental Rift From Source Mechanisms and Correlated Volcano‐Tectonic Earthquakes

Development of Late Jurassic‐Early Paleogene and Neogene‐Quaternary Rifts Within the Turkana Depression, East Africa From Satellite Gravity Data

Spatially Variable CO2 Degassing in the Main Ethiopian Rift: Implications for Magma Storage, Volatile Transport, and Rift‐Related Emissions

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Spatially Variable CO₂ Degassing in the Main Ethiopian Rift: Implications for Magma Storage, Volatile Transport, and Rift‐Related Emissions