Cattin, Rodolphe and Doubre, Cécile and de Chabalier, Jean-Bernard and King, Geoffrey and Vigny, Christophe and Avouac, Jean-Philippe and Ruegg, Jean-Claude (2005) Numerical modelling of quaternary deformation and post-rifting displacement in the Asal–Ghoubbet rift (Djibouti, Africa). Earth and Planetary Science Letters, 239 (3-4). pp. 352-367. ISSN 0012-821X http://resolver.caltech.edu/CaltechAUTHORS:20120906-142549966
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Over the last three decades a host of information on rifting process relating to the geological and thermal structure, long-time scale deformation (Quaternary and Holocene) and rifting cycle displacement across the Asal–Ghoubbet rift has been made available. These data are interpreted with a two-dimensional thermo-mechanical model that incorporates rheological layering of the lithosphere, dyke inflation and faulting. Active fault locations and geometry are mainly controlled by both thermal structure and magma intrusion into the crust. The distributed slip throughout the inner rift is related to the closeness of magma chamber, leading to additional stress into the upper thinned crust. Assuming a constant Arabia–Somalia motion of 11 mm/year, the variation of subsidence rate between the last 100 and 9 ka is associated with a decrease of the average injection rate from 10 to 5 mm/year. These values, about equal to the regional opening rate, suggest that both volcanism and tectonic play an equivalent role in the rifting process. Our modelled sequence of events gives one possible explanation for both vertical and horizontal displacements observed since the 1978 seismovolcanic crisis. Although part of the post-rifting deformation could be due to viscous relaxation, the high opening rate in the first years after the event and the abrupt velocity change in 1984–1986 argue for a large dyke inflation of 12 cm/year ending in 1985. The asymmetric and constant pattern of the GPS velocity since 1991 suggests that present post-rifting deformation is mainly controlled by fault creep and regional stretching. This study demonstrates the internal consistency of the data set, highlights the role of magmatism in the mechanics of crustal stretching and reveals a complex post-rifting process including magma injection, fault creep and regional stretching.
|Additional Information:||© 2005 Elsevier B.V. Received 2 November 2004; received in revised form 24 May 2005; accepted 25 July 2005. Available online 6 October 2005. Editor: V. Courtillot. This work was supported by the French program ACI Catastrophes Naturelles. We are grateful to many people who contributed to the field work since 1973. We greatly appreciated the discussions with Arnaud Mignan, Kurt Feigl, Isabelle Manighetti and Thora Arnadottir. The manuscript benefits from discussions with C. Ebinger and M. Casey. We thank Rebecca Bendick and Freysteinn Sigmundsson for constructive reviews, which greatly improve the manuscript. We thank Rebecca Bendick and Freysteinn Sigmundsson for constructive reviews, which greatly improve the manuscript. We thank Jean Chéry for providing the finite element code ADELI. All the figures were made with the GMT software (Wessel and Smith, 1991).|
|Subject Keywords:||Asal–Ghoubbet; rifting cycle; rift zone; fault creep; dyke inflation; magma injection|
|Official Citation:||Rodolphe Cattin, Cécile Doubre, Jean-Bernard de Chabalier, Geoffrey King, Christophe Vigny, Jean-Philippe Avouac, Jean-Claude Ruegg, Numerical modelling of quaternary deformation and post-rifting displacement in the Asal–Ghoubbet rift (Djibouti, Africa), Earth and Planetary Science Letters, Volume 239, Issues 3–4, 15 November 2005, Pages 352-367, ISSN 0012-821X, 10.1016/j.epsl.2005.07.028.|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||07 Sep 2012 16:39|
|Last Modified:||07 Sep 2012 16:39|
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