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The time scales of continental rifting: Implications for global processes

The time scales of continental rifting: Implications for global processes
The time scales of continental rifting: Implications for global processes
The rifting cycle initiates with stress buildup, release as earthquakes and/or magma intrusions/eruptions, and visco-elastic rebound, multiple episodes of which combine to produce the observed, time-averaged rift zone architecture. The aim of our synthesis of current research initiatives into continental rifting-to-rupture processes is to quantify the time and length scales of faulting and magmatism that produce the time-averaged rift structures imaged in active, failed rifts and passive margins worldwide. We compare and contrast seismic and geodetic strain patterns during discrete, intense rifting episodes in magmatic and amagmatic sectors of the East African rift zone that span early- to late-stage rifting. We also examine the longer term rifting cycle and its relation to changing far-field extension directions with examples from the Rio Grande rift zone and other cratonic rifts. Over time periods of millions of years, periods of rotating regional stress fields are marked by a lull in magmatic activity and a temporary halt to tectonic rift opening. Admittedly, rifting cycle comparisons are biased by the short time scale of global seismic and geodetic measurements, which span a small fraction of the 102–105 year rifting cycle. Within rift sectors with upper crustal magma chambers beneath the central rift valley (e.g., Main Ethiopian, Afar, and Eastern or Gregory rifts) seismic energy release accounts for a small fraction of the deformation; most of the strain is accommodated by magma intrusion and slow-slip. Magma intrusion processes appear to decrease the time period between rifting episodes, effectively accelerating the rift to rupture process. Thus, the inter-seismic period in rift zones with crustal magma reservoirs is strongly dependent upon the magma replenishment cycle. This comparison also demonstrates that intense rifting events, both magmatic and amagmatic, produce the long-term fault displacements and maintain the along-axis rift architecture through repeated episodes. The magmatic events in particular accommodate centuries of inter-seismic strain, implying that inter-seismic-plate opening rates in late stage rifts should be extrapolated to the past with caution.
0072-1077
371-396
Ebinger, C.J.
aedfe44b-76f6-4882-9522-0079fba9feda
van Wijk, J.
5af83237-380d-4c36-961c-6dc37aa3486d
Keir, D.
5616f81f-bf1b-4678-a167-3160b5647c65
Ebinger, C.J.
aedfe44b-76f6-4882-9522-0079fba9feda
van Wijk, J.
5af83237-380d-4c36-961c-6dc37aa3486d
Keir, D.
5616f81f-bf1b-4678-a167-3160b5647c65

Ebinger, C.J., van Wijk, J. and Keir, D. (2013) The time scales of continental rifting: Implications for global processes. Geological Society of America Special Papers, 500, 371-396. (doi:10.1130/2013.2500(11)).

Record type: Article

Abstract

The rifting cycle initiates with stress buildup, release as earthquakes and/or magma intrusions/eruptions, and visco-elastic rebound, multiple episodes of which combine to produce the observed, time-averaged rift zone architecture. The aim of our synthesis of current research initiatives into continental rifting-to-rupture processes is to quantify the time and length scales of faulting and magmatism that produce the time-averaged rift structures imaged in active, failed rifts and passive margins worldwide. We compare and contrast seismic and geodetic strain patterns during discrete, intense rifting episodes in magmatic and amagmatic sectors of the East African rift zone that span early- to late-stage rifting. We also examine the longer term rifting cycle and its relation to changing far-field extension directions with examples from the Rio Grande rift zone and other cratonic rifts. Over time periods of millions of years, periods of rotating regional stress fields are marked by a lull in magmatic activity and a temporary halt to tectonic rift opening. Admittedly, rifting cycle comparisons are biased by the short time scale of global seismic and geodetic measurements, which span a small fraction of the 102–105 year rifting cycle. Within rift sectors with upper crustal magma chambers beneath the central rift valley (e.g., Main Ethiopian, Afar, and Eastern or Gregory rifts) seismic energy release accounts for a small fraction of the deformation; most of the strain is accommodated by magma intrusion and slow-slip. Magma intrusion processes appear to decrease the time period between rifting episodes, effectively accelerating the rift to rupture process. Thus, the inter-seismic period in rift zones with crustal magma reservoirs is strongly dependent upon the magma replenishment cycle. This comparison also demonstrates that intense rifting events, both magmatic and amagmatic, produce the long-term fault displacements and maintain the along-axis rift architecture through repeated episodes. The magmatic events in particular accommodate centuries of inter-seismic strain, implying that inter-seismic-plate opening rates in late stage rifts should be extrapolated to the past with caution.

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More information

Published date: 2013
Organisations: Geology & Geophysics

Identifiers

Local EPrints ID: 360797
URI: http://eprints.soton.ac.uk/id/eprint/360797
ISSN: 0072-1077
PURE UUID: 01908f80-a545-4540-be14-069391c5ee2f
ORCID for D. Keir: ORCID iD orcid.org/0000-0001-8787-8446

Catalogue record

Date deposited: 23 Dec 2013 17:04
Last modified: 15 Mar 2024 03:38

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Contributors

Author: C.J. Ebinger
Author: J. van Wijk
Author: D. Keir ORCID iD

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