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Quantitative constraints on faulting and fault slip-rates in the northern Main Ethiopian Rift

Quantitative constraints on faulting and fault slip-rates in the northern Main Ethiopian Rift
Quantitative constraints on faulting and fault slip-rates in the northern Main Ethiopian Rift
The Boset magmatic segment (BMS) of the northern Main Ethiopian Rift (MER) is an ideal natural laboratory to investigate the kinematics, interaction, and rates of activity within a fault network in a magma‐rich rift. In this paper we take advantage of the availability of 1) high‐resolution remote sensing data (LiDAR, Aster); 2) absolute age chronology on offset reference surfaces; 3) well‐exposed active normal fault arrays to place new constraints on rift kinematics and strain distribution, and to quantify the architecture and fault slip‐rates at different temporal scales within a magmatic segment. We found that the rift border faults strike ~NE, while the younger faults in the rift segments strike NNE. Analyses of geometric rift parameters show that the axial active part of the rift is transtensional with an increase of the shear component northward. The fault displacement analyses and displacement: length ratios increase towards the segments tips suggesting a significant contribution of fault growth by linkage. In contrast, magmatism is focused on the segment centre and localized to a narrow zone. Estimated fault slip‐rates vary, with rates of up to ~0.37 mm/yr in ~0.3 Ma old rift floor deposits, whereas higher rates of up to ~4.4 mm/yr are observed for faults cutting through ~6 ka lavas. The difference in slip‐rates indicates short term variability or a very active recent episode compared to long‐term low average slip‐rates.
0278-7407
Siegburg, Melanie
b4801eca-cd00-401b-8cb0-a21da9754c42
Bull, Jonathan
974037fd-544b-458f-98cc-ce8eca89e3c8
Nixon, Casey
757fe329-f10f-4744-a28e-0ccc92217554
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Gernon, Thomas
658041a0-fdd1-4516-85f4-98895a39235e
Corti, Giacomo
dce88b12-5b7a-43b1-8a58-5bd1bc13634c
Abebe, Bekele
e22be781-cbe3-4882-8bc9-724426b0168b
Sanderson, David
5653bc11-b905-4985-8c16-c655b2170ba9
Ayele, Atalay
5b4eeb35-d229-4325-8940-d934dab7563d
Siegburg, Melanie
b4801eca-cd00-401b-8cb0-a21da9754c42
Bull, Jonathan
974037fd-544b-458f-98cc-ce8eca89e3c8
Nixon, Casey
757fe329-f10f-4744-a28e-0ccc92217554
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Gernon, Thomas
658041a0-fdd1-4516-85f4-98895a39235e
Corti, Giacomo
dce88b12-5b7a-43b1-8a58-5bd1bc13634c
Abebe, Bekele
e22be781-cbe3-4882-8bc9-724426b0168b
Sanderson, David
5653bc11-b905-4985-8c16-c655b2170ba9
Ayele, Atalay
5b4eeb35-d229-4325-8940-d934dab7563d

Siegburg, Melanie, Bull, Jonathan, Nixon, Casey, Keir, Derek, Gernon, Thomas, Corti, Giacomo, Abebe, Bekele, Sanderson, David and Ayele, Atalay (2020) Quantitative constraints on faulting and fault slip-rates in the northern Main Ethiopian Rift. Tectonics, [e2019TC006046]. (doi:10.1029/2019TC006046).

Record type: Article

Abstract

The Boset magmatic segment (BMS) of the northern Main Ethiopian Rift (MER) is an ideal natural laboratory to investigate the kinematics, interaction, and rates of activity within a fault network in a magma‐rich rift. In this paper we take advantage of the availability of 1) high‐resolution remote sensing data (LiDAR, Aster); 2) absolute age chronology on offset reference surfaces; 3) well‐exposed active normal fault arrays to place new constraints on rift kinematics and strain distribution, and to quantify the architecture and fault slip‐rates at different temporal scales within a magmatic segment. We found that the rift border faults strike ~NE, while the younger faults in the rift segments strike NNE. Analyses of geometric rift parameters show that the axial active part of the rift is transtensional with an increase of the shear component northward. The fault displacement analyses and displacement: length ratios increase towards the segments tips suggesting a significant contribution of fault growth by linkage. In contrast, magmatism is focused on the segment centre and localized to a narrow zone. Estimated fault slip‐rates vary, with rates of up to ~0.37 mm/yr in ~0.3 Ma old rift floor deposits, whereas higher rates of up to ~4.4 mm/yr are observed for faults cutting through ~6 ka lavas. The difference in slip‐rates indicates short term variability or a very active recent episode compared to long‐term low average slip‐rates.

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Accepted/In Press date: 6 July 2020
e-pub ahead of print date: 9 July 2020

Identifiers

Local EPrints ID: 442327
URI: http://eprints.soton.ac.uk/id/eprint/442327
ISSN: 0278-7407
PURE UUID: 075cb753-1f7e-4fb4-ab05-b844d2a41a45
ORCID for Derek Keir: ORCID iD orcid.org/0000-0001-8787-8446
ORCID for David Sanderson: ORCID iD orcid.org/0000-0002-2144-3527

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Date deposited: 13 Jul 2020 16:31
Last modified: 07 Oct 2020 01:59

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