A discussion on the structure and evolution of the Red Sea and the nature of the Red Sea, Gulf of Aden and Ethiopia rift junction - The structure of afar and the northern part of the ethiopian rift

1970 ◽  
Vol 267 (1181) ◽  
pp. 331-338 ◽  
Keyword(s):  
Red Sea ◽  
Rift Zone ◽  
Ethiopian Rift ◽  
Crustal Extension ◽  
Gulf Of Aden ◽  
Lateral Shear ◽  
Structural Pattern ◽  
Main Ethiopian Rift ◽  
The Individual ◽  
Complex Faulting

The major structural feature of the northern part of the Main Ethiopian Rift is an en échelon belt of Quaternary tensional faulting with the individual faults trending approximately N 20° E. Farther north, towards central Afar, this structural pattern gives way to a zone of complex faulting. Northern Afar is dominated by a linear, axial central rift region, marked by active fissure volcanism, normal faulting and open tensional faults, all trending generally NNW. However, this central rift zone dies out northwards as it is traced towards the Gulf of Zula. Left-lateral shear along the length of the Main Ethiopian Rift is proposed as the cause of the en echelon tensional fault zone, which can be traced into Afar, but is apparently not continuous with the zone of faulting associated with the median trough of the Red Sea. The latter appears to be replaced in an en echelon fashion southwards by zones of crustal extension in central and northern Afar.

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

2019 ◽  
Vol 6 (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.

A discussion on the structure and evolution of the Red Sea and the nature of the Red Sea, Gulf of Aden and Ethiopia rift junction - The structural pattern of the Afro-Arabian rift system in relation to plate tectonics

1970 ◽  
Vol 267 (1181) ◽  
pp. 383-391 ◽  
Keyword(s):  
Red Sea ◽  
Plate Tectonics ◽  
Structural Model ◽  
Structural Features ◽  
Dead Sea ◽  
Strike Slip ◽  
Rift System ◽  
Gulf Of Aden ◽  
Structural Pattern ◽  
The Dead

The structural pattern of the Afro-Arabian rift system suggests the influence of transcurrent faulting in the development of the main branches of the system, particularly along the Dead Sea rift, the Gulf of Suez and Red Sea, and the eastern rift of Africa. Geophysical evidence indicates that the Red Sea and Gulf of Aden formed as a result of the separation of the Arabian and African continental blocks. Previously determined rotation poles about which the blocks separated neglect some structural features of the region. A satisfactory refit of Arabia to Africa can­ not be made unless some relative movements of parts of the Africa block too place. It is proposed that dextral strike-slip movements took place between Africa and Arabia along the Red Sea and that sinistral strike-slip movements occurred along the Dead Sea rift. In addition, rotation of the E. Kenya-Somalia block east of the eastern rift of Africa took place. Structural and palaeomagnetic evidence supports such movements. The structural model is compatible with the observed tectonic pattern and provides a genetic link between the formation of the Red Sea, Gulf of Aden and the African rifts.

scholarly journals Waters from the Djiboutian Afar: A Review of Strontium Isotopic Composition and a Comparison with Ethiopian Waters and Red Sea Brines

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1700 ◽  
Author(s):  
Tiziano Boschetti ◽  
Mohamed Awaleh ◽  
Maurizio Barbieri
Keyword(s):  
Red Sea ◽  
Hot Springs ◽  
Ethiopian Rift ◽  
Concentration Data ◽  
Mixing Processes ◽  
Main Ethiopian Rift ◽  
Weathering Processes ◽  
Sea Bottom ◽  
Geochemical Studies ◽  
Freshwater Aquifers

Drinking water is scarce in Djibouti because of the hot desert climate. Moreover, seawater intrusion or fossil saltwater contamination of the limited number of freshwater aquifers due to groundwater overexploitation affect those who live close to the coastline (~80% of the population). Despite this, the geothermal potential of the country’s plentiful hot springs could resolve the increasing electricity demand. Strontium isotopes (87Sr/86Sr) are routinely used to determine sources and mixing relationships in geochemical studies. They have proven to be useful in determining weathering processes and quantifying endmember mixing processes. In this study, we summarise and reinterpret the 87Sr/86Sr ratio and Sr concentration data of the groundwater collected to date in the different regions of the Djibouti country, trying to discriminate between the different water sources, to evaluate the water/rock ratio and to compare the data with those coming from the groundwater in the neighbouring Main Ethiopian Rift and the Red Sea bottom brine. New preliminary data from the groundwater of the Hanlé-Gaggadé plains are also presented.

scholarly journals Lithospheric modification during crustal extension in the Main Ethiopian Rift

2007 ◽  
Vol 112 (B10) ◽  
Author(s):  
Tyrone Rooney ◽  
Tanya Furman ◽  
Ian Bastow ◽  
Dereje Ayalew ◽  
Gezahegn Yirgu
Keyword(s):  
Ethiopian Rift ◽  
Crustal Extension ◽  
Main Ethiopian Rift

A discussion on the structure and evolution of the Red Sea and the nature of the Red Sea, Gulf of Aden and Ethiopia rift junction - The development of the Red Sea and Gulf of Aden in relation to plate tectonics (summary only)

1970 ◽  
Vol 267 (1181) ◽  
pp. 393-395 ◽  
Keyword(s):  
Red Sea ◽  
Relative Motion ◽  
Plate Tectonics ◽  
Basic Assumption ◽  
Continental Drift ◽  
Ocean Floor ◽  
Ethiopian Rift ◽  
Gulf Of Aden ◽  
North West ◽  
The Earth

The ideas of Hess and Dietz on seafloor spreading were principally concerned with the produc­tion of ocean floor on the axes of oceanic rifts. The continents were believed to move with the surrounding ocean floor, and to remain undeformed during their motion. These are also the ideas on which plate tectonics depends, though it differs from earlier theories by imposing rather severe restrictions on the possible relative motions. The basic assumption in plate tectonics is that the surface of the Earth may be divided into many rigid aseismic plates in relative motion. The boundaries of the plates are defined by the seismic zones of the world, earthquakes being the expression of the relative motion between neighbouring plates. Since the relative motion of any two plates may be completely described by a rigid body rotation of one about some axis through the centre of the Earth, all problems concerned with present-day continental drift and tectonics reduce to the problem of determining the axes of relative rotation and angular velocities of all pairs of plates in contact. There is now abundant evidence to show that the basic assumption of plate tectonics is correct (McKenzie & Parker 1967; Morgan 1968; Le Pichon 1968; Isacks et al . 1968). The evolution of the Red Sea and the Gulf of Aden is a consequence of the motions of at least four plates: Arabia, the north-west Indian Ocean, Africa east of the rift and Africa west of the rift. The motion between Arabia and east Africa is well determined from observations in the Gulf of Aden, but that between Arabia and west Africa must be obtained by fitting Arabia on to Africa by closing the Red Sea. The motion on the Ethiopian rift can then be calculated.

A discussion on the structure and evolution of the Red Sea and the nature of the Red Sea, Gulf of Aden and Ethiopia rift junction - Tectonic significance of regional geology and evaporite lithfacies in northeastern ethiopia

1970 ◽  
Vol 267 (1181) ◽  
pp. 313-329 ◽  
Keyword(s):  
Red Sea ◽  
Tectonic Activity ◽  
Ethiopian Rift ◽  
Gulf Of Aden ◽  
Submarine Canyons ◽  
Ethiopian Plateau ◽  
Continental Shelves ◽  
Tectonic Significance ◽  
The Alps ◽  
Eastern Edge

Mesozoic and Precambrian rocks are exposed in the Danakil Alps of coastal Eritrea, but the Danakil Depression between the Alps and the Ethiopian plateau is covered by Tertiary-Quaternary rocks. The physiography, structural geology, regional stratigraphy and evaporite lithof acies distribution of this area all suggest that it is underlain by an asymmetrically subsided block of old sialic crust. The western edge of this block has subsided deeply along the Ethiopian rift and is covered, in the Danakil Depression, by an evaporite-basalt veneer, but its eastern edge has been uplifted as the Danakil Alps. These are bounded on the east by a rift escarpment facing the Red Sea. Although geologic data here is sparse compared to the Danakil region, certain features suggest that a similar asymmetrically subsided block of older sialic rocks, with an evaporite-basalt veneer, may also lie beneath much of the Red Sea. This tectonic evolution apparently commenced in Miocene time with rifting near the centre of an earlier Mesozoic-Paleogene sedimentary basin. Uplift along this central rift caused tensional failure along a secondarily induced rift to the west, and east-side-down subsidence along this structure formed the asymmetrically subsided block. There were apparently two successive cycles of this tectonic activity. The earlier, of Miocene age, formed the easterly (Red Sea) block with a thicker veneer of older evaporitebasalt, and the later, of Plio-Pleistocene age formed the westerly (Danakil) block with a thinner veneer of younger evaporite-basalt. The separation of Arabia from Ethiopia across the southern Red Sea would thus be relatively minor, presumably represented by the width of the Red Sea’s axial trough plus a few kilometres across each of the Danakil Alp and Ethiopian rifts. Similar tectonic developments may accompany initial rifting and separation in the development of ocean basins by seafloor spreading, and might explain why oceans like the Atlantic, that have apparently developed in this manner, are fringed by shallow continental shelves with thick evaporite sequences and steep walled submarine canyons.

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