AuthorsS. Clark, D. Stegman and D. R. Müller
TitleEpisodicity in Back-Arc Tectonic Regimes
AfilliationKalkulo, Center for Biomedical Computing (SFF), Scientific Computing
Project(s)Center for Biomedical Computing (SFF)
StatusPublished
Publication TypeJournal Article
Year of Publication2008
JournalPhysics of the Earth and Planetary Interiors
Volume171
NumberSpecial Issue on Recent Advanced in Computational Geodynamics: Theory, Numerics and Applications
Pagination265-279
Date PublishedNovember
PublisherElsevier
Abstract

The evolution of back-arc basins is tied to the development of the dynamics of the subduction system they are a part of. We present a study of back-arc basins and model their development by implementing 3-D time-dependant computer models of subduction including an overriding plate. We define three types of episodicity - pseudo-, quasi- and hyper-episodicity, and find evidence of these in nature. Quasi-episodicity, in which the back-arc shifts between phases of rifting/spreading and quiescence, is the dominant form of episodic back-arc development in the present. We find this type of episodicity in models for which the system is dynamically consistent - that we have allowed the subducting plate's velocity to be determined by the sinking slabs' buoyancy. Hyper-episodicity occurs in models that are driven by an imposed velocity boundary condition. In this case the full range of behaviour is witnessed - trench advance, retreat and stability. In nature, this occurs rarely, but may occur in places that undergo sudden shifts in plate tectonics and that are therefore unable to self-balance within a noticeable period. Pseudo-episodicity is a category for back-arc rifting or spreading that seems to be periodic, but is really related to ridge-jumps and the brittle nature of the overriding plate. Constant rollback and pseudo-episodic back-arc rifting are witnessed in places where the subducting plate's motion is inhibited by a retarding force, at the trailing edge in our models. This may be, for example, a continent or another subduction zone. Records of back-arc basin rifting/spreading and quiescence from oceanic paleo-age grids have been observed and further validate the conceptual division of epsidocity into these three categories.

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