Eruptive frequency of the Bora-Baricha-Tullu Moye (BBTM) volcanic system in the Central Main Ethiopian Rift

The Main Ethiopian Rift (MER) is the northern portion of the East African Rift System and separates the Eastern and Western plateaus of Ethiopia. The recent volcanic and tectonic activity is largely focused within the rift basin along a 20 km wide zone on the rift floor. Large silicic volcanic complexes are aligned along this central rift axis but their eruptive histories are not well constrained.The Bora-Baricha-Tullu Moye (BBTM) volcanic field is situated in the central Main Ethiopian Rift and has a different appearance than the other MER volcanic systems. The BBTM constitutes several late Quaternary edifices, the major ones are: Tullu Moye, Bora and Baricha. In addition, there are multiple smaller eruptive vents (e.g. Oda and Dima), cones, and domes across the ca. 20 X 20 km wide area. Currently, there is very little information on the frequency and magnitude of past volcanic eruptions. We present a new dataset of field observations, componentry, petrography, geochronology (40Ar/39Ar), and glass major and trace element chemistry. The data are assessed as potential fingerprints to assign diagnostic features and correlate units across the area, and establish a tephrostratigraphic framework for the BBTM volcanic field.Two large-volume and presumably caldera-forming eruptions are identified, the younger of which took place at 100 ka. The volcanic products exposed in the BBTM area show that the volcanic field has undergone at least 20 explosive eruptions since then. The post-caldera eruptions have comenditic (Tullu Moye) and pantelleretic (Bora and Baricha) magma compositions. Other smaller edifices such as Oda and Dima also erupted pantelleritic magmas, and only differ slightly in composition than tephra of Bora and Baricha. Tullu Moye had two distinct explosive eruptions that dispersed tephra up to 14 km away and on to the eastern plateau. Bora and Baricha together had at least 8 explosive eruptions. Their deposits can be distinguished by their light grey color and unique lithic components. Oda had 7 eruptions, the most recent of which generated a pyroclastic density current that travelled up to 10 km away from the vent. Dima experienced at least 3 eruptions, generating tephra with a bluish-grey colour.This mapping and compositional analysis of the deposits from the BBTM in the MER indicates that the region has been more active in the last 100 ka than previously thought, which has implications for hazards assessments for the region.

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Off-axis volcano-tectonic activity during continental rifting: Insights from the transversal Goba-Bonga lineament, Main Ethiopian Rift (East Africa)

Tectonophysics ◽

10.1016/j.tecto.2018.02.011 ◽

2018 ◽

Vol 728-729 ◽

pp. 75-91 ◽

Cited By ~ 9

Author(s):

Giacomo Corti ◽

Federico Sani ◽

Samuele Agostini ◽

Melody Philippon ◽

Dimitrios Sokoutis ◽

...

Keyword(s):

East Africa ◽

Tectonic Activity ◽

Ethiopian Rift ◽

Continental Rifting ◽

Main Ethiopian Rift

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The Christiana–Santorini–Kolumbo Volcanic Field

Elements ◽

10.2138/gselements.15.3.171 ◽

2019 ◽

Vol 15 (3) ◽

pp. 171-176 ◽

Cited By ~ 2

Author(s):

Paraskevi Nomikou ◽

Christian Hübscher ◽

Steven Carey

Keyword(s):

Eastern Mediterranean ◽

Eastern Mediterranean Region ◽

Aegean Sea ◽

Volcanic Eruptions ◽

Volcanic Field ◽

Explosive Eruptions ◽

Human Populations ◽

Mass Wasting ◽

Geological Processes ◽

Research Activities

The Christiana–Santorini–Kolumbo volcanic field in the South Aegean Sea (Greece) is one of the most important in Europe, having produced more than 100 explosive eruptions in the last 400,000 years. Its volcanic centers include the extinct Christiana Volcano and associated seamounts, Santorini caldera with its intracaldera Kameni Volcano, Kolumbo Volcano, and 24 other submarine cones of the Kolumbo chain. Earthquakes, volcanic eruptions, submarine mass wasting, neotectonics and gas releases from these centers pose significant geohazards to human populations and infrastructures of the Eastern Mediterranean region. Defining the geological processes and structures that contribute to these geohazards will provide an important framework to guide future monitoring and research activities aimed at hazard mitigation.

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The Impact of Complex Volcanic Plumbing on the Nature of Seismicity in the Developing Magmatic Natron Rift, Tanzania

Frontiers in Earth Science ◽

10.3389/feart.2020.609805 ◽

2021 ◽

Vol 8 ◽

Author(s):

Miriam Christina Reiss ◽

James D. Muirhead ◽

Amani S. Laizer ◽

Frederik Link ◽

Emmanuel O. Kazimoto ◽

...

Keyword(s):

Volcanic Field ◽

Tectonic Activity ◽

Rift System ◽

East African Rift System ◽

Oldoinyo Lengai ◽

Fault Plane Solutions ◽

Magma Body ◽

Volcanic Plumbing System ◽

Stress Changes ◽

The Impact

Constraining the architecture of complex 3D volcanic plumbing systems within active rifts, and their impact on rift processes, is critical for examining the interplay between faulting, magmatism and magmatic fluids in developing rift segments. The Natron basin of the East African Rift System provides an ideal location to study these processes, owing to its recent magmatic-tectonic activity and ongoing active carbonatite volcanism at Oldoinyo Lengai. Here, we report seismicity and fault plane solutions from a 10 month-long temporary seismic network spanning Oldoinyo Lengai, Naibor Soito volcanic field and Gelai volcano. We locate 6,827 earthquakes with ML −0.85 to 3.6, which are related to previous and ongoing magmatic and volcanic activity in the region, as well as regional tectonic extension. We observe seismicity down to ∼17 km depth north and south of Oldoinyo Lengai and shallow seismicity (3–10 km) beneath Gelai, including two swarms. The deepest seismicity (∼down to 20 km) occurs above a previously imaged magma body below Naibor Soito. These seismicity patterns reveal a detailed image of a complex volcanic plumbing system, supporting potential lateral and vertical connections between shallow- and deep-seated magmas, where fluid and melt transport to the surface is facilitated by intrusion of dikes and sills. Focal mechanisms vary spatially. T-axis trends reveal dominantly WNW-ESE extension near Gelai, while strike-slip mechanisms and a radial trend in P-axes are observed in the vicinity of Oldoinyo Lengai. These data support local variations in the state of stress, resulting from a combination of volcanic edifice loading and magma-driven stress changes imposed on a regional extensional stress field. Our results indicate that the southern Natron basin is a segmented rift system, in which fluids preferentially percolate vertically and laterally in a region where strain transfers from a border fault to a developing magmatic rift segment.

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Quaternary volcano-tectonic activity in the Soddo region, western margin of the Southern Main Ethiopian Rift

Tectonics ◽

10.1002/tect.20052 ◽

2013 ◽

pp. n/a-n/a ◽

Cited By ~ 7

Author(s):

Giacomo Corti ◽

Federico Sani ◽

Melody Philippon ◽

Dimitrios Sokoutis ◽

Ernst Willingshofer ◽

...

Keyword(s):

Tectonic Activity ◽

Ethiopian Rift ◽

Main Ethiopian Rift ◽

Western Margin ◽

Quaternary Volcano

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Water Resource Assessment of a Complex Volcanic System Under Semi-Arid Climate Using Numerical Modeling: The Borena Basin in Southern Ethiopia

Water ◽

10.3390/w12010276 ◽

2020 ◽

Vol 12 (1) ◽

pp. 276

Author(s):

Moumtaz Razack ◽

Wakgari Furi ◽

Likissa Fanta ◽

Abera Shiferaw

Keyword(s):

Surface Waters ◽

Regional Model ◽

Arid Climate ◽

Southern Ethiopia ◽

Ethiopian Rift ◽

Sustainable Yield ◽

Volcanic System ◽

Main Ethiopian Rift ◽

Semi Arid ◽

Natural Recharge

The Borena basin is located in southern Ethiopia, in a semi-arid climate, on the eastern shoulder of the south Main Ethiopian Rift (MER). The study area covers 18,000 km2 and is characterized by a lack of perennial surface waters that can be used for domestic and agricultural purpose. As a result, groundwater, which occurs in complex volcanic settings, is the only source for water supply in the study area. This work is focused on the basaltic aquifers, which are intensely fractured, resulting in strong connectivity within the system. All available data (geology, hydraulic head, hydraulic parameters, well inventory and discharge, etc.) were compiled in a GIS database. The overall objective of this work is the assessment of groundwater potential, its spatial distribution and factors controlling its movement using numerical groundwater modeling to enhance groundwater management and use in the Borena basin. The modeling task was conducted at two scales: (i) regional scale; (ii) wellfields scale. The regional steady state model was calibrated using the Pilot points approach, highlighting a strongly heterogeneous system. A significant result of the regional model consisted of estimating the water balance of the whole system. The total inflow to the basin amounts to 542 × 106 m3/year, of which 367 × 106 m3/year are provided by superficial recharge. Groundwater resources are exploited with 7 wellfields. Exploitation of the wellfields was optimized based on the Sustainable Yield concept, which reserves a fraction of natural recharge for the benefit of the environment (surface waters, ecosystems). Each wellfield was extracted from the regional model, refined and used to simulate and optimize pumping scenarios, with the objective of maximizing discharge rates and avoiding over-exploitation of the groundwater. The optimized abstraction at all wellfields amounts to 121 × 106 m3/year, which represents 33% of the natural recharge and fully agrees with the sustainable yield concept.

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A review on the multi-criteria seismic hazard analysis of Ethiopia: with implications of infrastructural development

Geoenvironmental Disasters ◽

10.1186/s40677-020-00175-7 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Alemayehu Ayele ◽

Kifle Woldearegay ◽

Matebie Meten

Keyword(s):

Seismic Hazard ◽

Ground Motion ◽

Active Fault ◽

Site Response ◽

Seismic Hazard Assessment ◽

Earthquake Ground Motion ◽

Response Analysis ◽

Ethiopian Rift ◽

Rift System ◽

Main Ethiopian Rift

AbstractEarthquake is a sudden release of energy due to faults. Natural calamities like earthquakes can neither be predicted nor prevented. However, the severity of the damages can be minimized by development of proper infrastructure which includes microzonation studies, appropriate construction procedures and earthquake resistant designs. The earthquake damaging effect depends on the source, path and site conditions. The earthquake ground motion is affected by topography (slope, hill, valley, canyon, ridge and basin effects), groundwater and surface hydrology. The seismic hazard damages are ground shaking, structural damage, retaining structure failures and lifeline hazards. The medium to large earthquake magnitude (< 6) reported in Ethiopia are controlled by the main Ethiopian rift System. The spatial and temporal variation of earthquake ground motion should be addressed using the following systematic methodology. The general approaches used to analyze damage of earthquake ground motions are probabilistic seismic hazard assessment (PSHA), deterministic seismic hazard assessment (DSHA) and dynamic site response analysis. PSHA considers all the scenarios of magnitude, distance and site conditions to estimate the intensity of ground motion distribution. Conversely, DSHA taken into account the worst case scenarios or maximum credible earthquake to estimate the intensity of seismic ground motion distribution. Furthermore, to design critical infrastructures, DSHA is more valuable than PSHA. The DSHA and PSHA ground motion distributions are estimated as a function of earthquake magnitude and distance using ground motion prediction equations (GMPEs) at top of the bedrock. Site response analysis performed to estimate the ground motion distributions at ground surface using dynamic properties of the soils such as shear wave velocity, density, modulus reduction, and material damping curves. Seismic hazard evaluation of Ethiopia shown that (i) amplification is occurred in the main Ethiopian Rift due to thick soil, (ii) the probability of earthquake recurrence due to active fault sources. The situation of active fault is oriented in the N-S direction. Ethiopia is involved in huge infrastructural development (including roads, industrial parks and railways), increasing population and agricultural activity in the main Ethiopian Rift system. In this activity, socio-economic development, earthquake and earthquake-generated ground failures need to be given attention in order to reduce losses from seismic hazards and create safe geo-environment.

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The Ziway–Shala lake basin (main Ethiopian rift, Ethiopia): a revision of basin evolution with special reference to the Late Quaternary

Journal of African Earth Sciences ◽

10.1016/s0899-5362(02)00036-2 ◽

2002 ◽

Vol 35 (2) ◽

pp. 247-269 ◽

Cited By ~ 67

Author(s):

M Benvenuti ◽

S Carnicelli ◽

G Belluomini ◽

N Dainelli ◽

S Di Grazia ◽

...

Keyword(s):

Special Reference ◽

Late Quaternary ◽

Ethiopian Rift ◽

Lake Basin ◽

Basin Evolution ◽

Main Ethiopian Rift

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Homogenized earthquake catalog and b-value mapping for Ethiopia and its adjoining regions

Geoenvironmental Disasters ◽

10.1186/s40677-019-0131-y ◽

2019 ◽

Vol 6 (1) ◽

Cited By ~ 1

Author(s):

Geremew Lamessa ◽

Tilahun Mammo ◽

Tarun K.Raghuvanshi

Keyword(s):

Red Sea ◽

B Value ◽

Moment Magnitude ◽

Ethiopian Rift ◽

Rift System ◽

Earthquake Catalog ◽

Gulf Of Aden ◽

East African Rift System ◽

Main Ethiopian Rift ◽

B Values

AbstractThe Ethiopian rift which is part of East African Rift system passes through the middle of the country making it one of the most seismically active regions in the world. Thus, significant and damaging earthquakes have been reported and recorded in the past in this region. A homogeneous earthquake catalog is of basic importance for studying the earthquake occurrence pattern in space and time and for many engineering applications including assessment of seismic hazard, estimation of peak ground accelerations and determination of long-term seismic strain rates.The first earthquake catalogue for Ethiopia was prepared by Pierre Gouin and later, different authors attempted to compile a catalogue using different time period intervals and different earthquake magnitude scales. The b-value mapping and its implication never done for Ethiopia and its environs. The main purpose of the study is therefore first compile and homogenize earthquake catalog of Ethiopia including Read Sea and Gulf of Aden regions into Moment magnitude Mw scale through completeness analysis in time and magnitudes. Secondly, mapping b-values for different Seismgenic regions and understand its implications for magma induced Seismicity in the regions.During the present study, a new homogenized earthquake catalog in moment magnitude scale (Mw), covering about 3814 events is prepared for Ethiopia including Red sea and Gulf of Aden regions. The present study area is bounded within Latitude (40N − 200)N and Longitude (340N − 480)N E and have a magnitude range of Mw (3.0–7.1) with a total coverage period of 56 years (1960 to 2016). The catalog has been analyzed for magnitude completeness (Mc) using Gutenberg’s Frequency Magnitude Distribution law and it is found to be complete respectively for Mc ≥ 4.6 ± 0.03, Mc ≥ 4.6 ± 0.03, Mc ≥ 3.2, Mc ≥ 3.1 and Mc ≥ 5.1 for Afar including red sea and Gulf of Aden, Afar rift and Dabbahu Volcano, Northern, Central, and Southern Main Ethiopian Rifts. Further, the corresponding average b-value of the regions Afar including Red Sea and Gulf of Aden, Afar and Dabbahu Volcano separately, Northern Main Ethiopian Rift, Central Main Ethiopian Rift and Southern Main Ethiopian Rift respectively are estimated to be 1.17 ± 0.05, 1.15 ± 0.05, 0.843, 0.826 and 1.03 with respective period of completeness from 2003 to 2014, 2005 to 2014, 2001 to 2003, 2001 to 2003 and 1960 to 2016 for the regions. Later, mapping of the b-values in the Gutenberg-Richter relation from the newly developed catalog was performed by binning the regions into minimum of 0.050x0.050 for Afar and Dabbahu region, 0.10x0.10 for Main Ethiopian rifts and 0.20x0.20 for the other regions. Thus, the b-value characteristics of various seismogenic zones within the area have been discussed. Hence, in this study, we clearly observed that magma chamber movement including mapping of volcanic centers and magmatic segments are mapped using b-values.

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