Geodetic constraints on cratonic microplates and broad strain during rifting of thick Southern African lithosphere

Luke N J Wedmore; Juliet J Biggs; Michael Floyd; Åke Fagereng; H. Mdala; Patrick Chindandali; Jack N Williams; Felix Mphepo

doi:10.1029/2021GL093785

Geodetic constraints on cratonic microplates and broad strain during rifting of thick Southern African lithosphere

Luke N J Wedmore, Juliet J Biggs, Michael Floyd, Åke Fagereng, H. Mdala, Patrick Chindandali, Jack N Williams, Felix Mphepo

Research output: Contribution to journal › Article (Academic Journal) › peer-review

39 Citations (Scopus)

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Abstract

Southern Africa is typically considered to belong to a single tectonic plate, Nubia, despite active faulting along the southwestern branch of the East African Rift System. We analyse regional GNSS measurements, and find that the ‘San’ microplate, situated south of the southwestern branch of the East African Rift, is statistically distinct from Nubia, with 0.4-0.7 mm/yr of extension across the boundary. Adding 9 new campaign GNSS sites, we show that the extension rate across the southern Malawi Rift is 2.2 ± 0.3 mm/yr, with 75% of the relative velocity occurring over 890 km, despite the surface expression of faulting being <150 km wide. Thus, for the first time, we use geodetic measurements to describe the accommodation of strain in broad zones between Archean cratons in southern Africa’s thick continental lithosphere.

Original language	English
Article number	e2021GL093785
Journal	Geophysical Research Letters
Volume	48
Issue number	17
Early online date	6 Aug 2021
DOIs	https://doi.org/10.1029/2021GL093785
Publication status	Published - 16 Sept 2021

Bibliographical note

Funding Information:
The authors thank Kondwani Dombola, Denson Makwela, and Jalf Salima at the Geological Survey Department, Malawi for making this work possible. The authors also thank the district governors, drivers, schoolteachers, doctors, national park wardens, and guards in Malawi for assistance with the GPS deployment. We thank Ophelia George for her assistance in uploading the GNSS data to Unavco. The authors thank the Cindy Ebinger, two other reviewers, and the associate editor for careful and detailed comments that significantly improved this manuscript. This work was funded by a number of EPSRC grants funded under the Global Challenges Research Fund (GCRF): PREPARE (EP/P028233/1); SAFER PREPARED (part of the “Innovative data services for aquaculture, seismic resilience, and drought adaptation in East Africa” grant; EP/T015462/1); and a GCRF EPSRC Institutional Sponsorship Award. The authors also received a fieldwork grant from COMET, the NERC Centre for the Observation and Modeling of Earthquakes, Volcanoes, and Tectonics, a partnership between UK Universities and the British Geological Survey. This material is based on services provided by the GAGE Facility, operated by UNAVCO, Inc., with the support from the National Science Foundation and the National Aeronautics and Space Administration under NSF Cooperative Agreement EAR‐1724794.

Funding Information:
The authors thank Kondwani Dombola, Denson Makwela, and Jalf Salima at the Geological Survey Department, Malawi for making this work possible. The authors also thank the district governors, drivers, schoolteachers, doctors, national park wardens, and guards in Malawi for assistance with the GPS deployment. We thank Ophelia George for her assistance in uploading the GNSS data to Unavco. The authors thank the Cindy Ebinger, two other reviewers, and the associate editor for careful and detailed comments that significantly improved this manuscript. This work was funded by a number of EPSRC grants funded under the Global Challenges Research Fund (GCRF): PREPARE (EP/P028233/1); SAFER PREPARED (part of the ?Innovative data services for aquaculture, seismic resilience, and drought adaptation in East Africa? grant; EP/T015462/1); and a GCRF EPSRC Institutional Sponsorship Award. The authors also received a fieldwork grant from COMET, the NERC Centre for the Observation and Modeling of Earthquakes, Volcanoes, and Tectonics, a partnership between UK Universities and the British Geological Survey. This material is based on services provided by the GAGE Facility, operated by UNAVCO, Inc., with the support from the National Science Foundation and the National Aeronautics and Space Administration under NSF Cooperative Agreement EAR-1724794.

Publisher Copyright:
© 2021. The Authors.

Keywords

GNSS
plate tectonics
Africa
geodesy
strain
rift

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10.1029/2021GL093785

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39 Citations
1 Other contribution

Malawi PREPARE 2016-2019 - GPS/GNSS Observations
Biggs, J. J., Wedmore, L. N. J. & Mdala, H., 27 Jul 2021, The Gage Facility operated by UNAVCO, Inc.
Research output: Other contribution

Open Access

2 Finished

8035 GCRF GLOBAL RESEARCH TRANSLATIONAL AWARDS EP/T015462/1 - SAFER PREPARED
Sextos, A. (Principal Investigator), Macdonald, J. H. G. (Co-Investigator), Biggs, J. J. (Co-Investigator), De Risi, R. (Co-Investigator), Werner, M. (Co-Investigator), Agarwal, J. (Co-Investigator) & De Luca, F. (Co-Investigator)
1/10/19 → 31/03/22
Project: Research
PREPARE: Enhancing PREParedness for East African Countries through Seismic Resilience Engineering
Biggs, J. J. (Principal Investigator) & Macdonald, J. H. G. (Principal Investigator)
1/05/17 → 31/03/22
Project: Research, Parent

Cite this

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title = "Geodetic constraints on cratonic microplates and broad strain during rifting of thick Southern African lithosphere",

abstract = "Southern Africa is typically considered to belong to a single tectonic plate, Nubia, despite active faulting along the southwestern branch of the East African Rift System. We analyse regional GNSS measurements, and find that the {\textquoteleft}San{\textquoteright} microplate, situated south of the southwestern branch of the East African Rift, is statistically distinct from Nubia, with 0.4-0.7 mm/yr of extension across the boundary. Adding 9 new campaign GNSS sites, we show that the extension rate across the southern Malawi Rift is 2.2 ± 0.3 mm/yr, with 75% of the relative velocity occurring over 890 km, despite the surface expression of faulting being <150 km wide. Thus, for the first time, we use geodetic measurements to describe the accommodation of strain in broad zones between Archean cratons in southern Africa{\textquoteright}s thick continental lithosphere.",

keywords = "GNSS, plate tectonics, Africa, geodesy, strain, rift",

author = "Wedmore, {Luke N J} and Biggs, {Juliet J} and Michael Floyd and {\AA}ke Fagereng and H. Mdala and Patrick Chindandali and Williams, {Jack N} and Felix Mphepo",

note = "Funding Information: The authors thank Kondwani Dombola, Denson Makwela, and Jalf Salima at the Geological Survey Department, Malawi for making this work possible. The authors also thank the district governors, drivers, schoolteachers, doctors, national park wardens, and guards in Malawi for assistance with the GPS deployment. We thank Ophelia George for her assistance in uploading the GNSS data to Unavco. The authors thank the Cindy Ebinger, two other reviewers, and the associate editor for careful and detailed comments that significantly improved this manuscript. This work was funded by a number of EPSRC grants funded under the Global Challenges Research Fund (GCRF): PREPARE (EP/P028233/1); SAFER PREPARED (part of the “Innovative data services for aquaculture, seismic resilience, and drought adaptation in East Africa” grant; EP/T015462/1); and a GCRF EPSRC Institutional Sponsorship Award. The authors also received a fieldwork grant from COMET, the NERC Centre for the Observation and Modeling of Earthquakes, Volcanoes, and Tectonics, a partnership between UK Universities and the British Geological Survey. This material is based on services provided by the GAGE Facility, operated by UNAVCO, Inc., with the support from the National Science Foundation and the National Aeronautics and Space Administration under NSF Cooperative Agreement EAR‐1724794. Funding Information: The authors thank Kondwani Dombola, Denson Makwela, and Jalf Salima at the Geological Survey Department, Malawi for making this work possible. The authors also thank the district governors, drivers, schoolteachers, doctors, national park wardens, and guards in Malawi for assistance with the GPS deployment. We thank Ophelia George for her assistance in uploading the GNSS data to Unavco. The authors thank the Cindy Ebinger, two other reviewers, and the associate editor for careful and detailed comments that significantly improved this manuscript. This work was funded by a number of EPSRC grants funded under the Global Challenges Research Fund (GCRF): PREPARE (EP/P028233/1); SAFER PREPARED (part of the ?Innovative data services for aquaculture, seismic resilience, and drought adaptation in East Africa? grant; EP/T015462/1); and a GCRF EPSRC Institutional Sponsorship Award. The authors also received a fieldwork grant from COMET, the NERC Centre for the Observation and Modeling of Earthquakes, Volcanoes, and Tectonics, a partnership between UK Universities and the British Geological Survey. This material is based on services provided by the GAGE Facility, operated by UNAVCO, Inc., with the support from the National Science Foundation and the National Aeronautics and Space Administration under NSF Cooperative Agreement EAR-1724794. Publisher Copyright: {\textcopyright} 2021. The Authors.",

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language = "English",

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AU - Biggs, Juliet J

AU - Floyd, Michael

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AU - Chindandali, Patrick

AU - Williams, Jack N

AU - Mphepo, Felix

N1 - Funding Information: The authors thank Kondwani Dombola, Denson Makwela, and Jalf Salima at the Geological Survey Department, Malawi for making this work possible. The authors also thank the district governors, drivers, schoolteachers, doctors, national park wardens, and guards in Malawi for assistance with the GPS deployment. We thank Ophelia George for her assistance in uploading the GNSS data to Unavco. The authors thank the Cindy Ebinger, two other reviewers, and the associate editor for careful and detailed comments that significantly improved this manuscript. This work was funded by a number of EPSRC grants funded under the Global Challenges Research Fund (GCRF): PREPARE (EP/P028233/1); SAFER PREPARED (part of the “Innovative data services for aquaculture, seismic resilience, and drought adaptation in East Africa” grant; EP/T015462/1); and a GCRF EPSRC Institutional Sponsorship Award. The authors also received a fieldwork grant from COMET, the NERC Centre for the Observation and Modeling of Earthquakes, Volcanoes, and Tectonics, a partnership between UK Universities and the British Geological Survey. This material is based on services provided by the GAGE Facility, operated by UNAVCO, Inc., with the support from the National Science Foundation and the National Aeronautics and Space Administration under NSF Cooperative Agreement EAR‐1724794. Funding Information: The authors thank Kondwani Dombola, Denson Makwela, and Jalf Salima at the Geological Survey Department, Malawi for making this work possible. The authors also thank the district governors, drivers, schoolteachers, doctors, national park wardens, and guards in Malawi for assistance with the GPS deployment. We thank Ophelia George for her assistance in uploading the GNSS data to Unavco. The authors thank the Cindy Ebinger, two other reviewers, and the associate editor for careful and detailed comments that significantly improved this manuscript. This work was funded by a number of EPSRC grants funded under the Global Challenges Research Fund (GCRF): PREPARE (EP/P028233/1); SAFER PREPARED (part of the ?Innovative data services for aquaculture, seismic resilience, and drought adaptation in East Africa? grant; EP/T015462/1); and a GCRF EPSRC Institutional Sponsorship Award. The authors also received a fieldwork grant from COMET, the NERC Centre for the Observation and Modeling of Earthquakes, Volcanoes, and Tectonics, a partnership between UK Universities and the British Geological Survey. This material is based on services provided by the GAGE Facility, operated by UNAVCO, Inc., with the support from the National Science Foundation and the National Aeronautics and Space Administration under NSF Cooperative Agreement EAR-1724794. Publisher Copyright: © 2021. The Authors.

PY - 2021/9/16

Y1 - 2021/9/16

N2 - Southern Africa is typically considered to belong to a single tectonic plate, Nubia, despite active faulting along the southwestern branch of the East African Rift System. We analyse regional GNSS measurements, and find that the ‘San’ microplate, situated south of the southwestern branch of the East African Rift, is statistically distinct from Nubia, with 0.4-0.7 mm/yr of extension across the boundary. Adding 9 new campaign GNSS sites, we show that the extension rate across the southern Malawi Rift is 2.2 ± 0.3 mm/yr, with 75% of the relative velocity occurring over 890 km, despite the surface expression of faulting being <150 km wide. Thus, for the first time, we use geodetic measurements to describe the accommodation of strain in broad zones between Archean cratons in southern Africa’s thick continental lithosphere.

AB - Southern Africa is typically considered to belong to a single tectonic plate, Nubia, despite active faulting along the southwestern branch of the East African Rift System. We analyse regional GNSS measurements, and find that the ‘San’ microplate, situated south of the southwestern branch of the East African Rift, is statistically distinct from Nubia, with 0.4-0.7 mm/yr of extension across the boundary. Adding 9 new campaign GNSS sites, we show that the extension rate across the southern Malawi Rift is 2.2 ± 0.3 mm/yr, with 75% of the relative velocity occurring over 890 km, despite the surface expression of faulting being <150 km wide. Thus, for the first time, we use geodetic measurements to describe the accommodation of strain in broad zones between Archean cratons in southern Africa’s thick continental lithosphere.

KW - GNSS

KW - plate tectonics

KW - Africa

KW - geodesy

KW - strain

KW - rift

U2 - 10.1029/2021GL093785

DO - 10.1029/2021GL093785

M3 - Article (Academic Journal)

SN - 0094-8276

VL - 48

JO - Geophysical Research Letters

JF - Geophysical Research Letters

IS - 17

M1 - e2021GL093785

ER -

Geodetic constraints on cratonic microplates and broad strain during rifting of thick Southern African lithosphere

Abstract

Bibliographical note

Keywords

Access to Document

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Research output

Malawi PREPARE 2016-2019 - GPS/GNSS Observations

Projects

8035 GCRF GLOBAL RESEARCH TRANSLATIONAL AWARDS EP/T015462/1 - SAFER PREPARED

PREPARE: Enhancing PREParedness for East African Countries through Seismic Resilience Engineering

Cite this