At a subduction zone the amount of friction between the incoming plate and the forearc is an important factor in controlling the dip angle of subduction and the structure of the forearc. In this paper, we investigate the role of the frictional strength of sediments and of the serpentinized peridotite on the evolution of convergent margins. In numerical models, we vary thickness of a serpentinized layer in the mantle wedge (15 to 25km) and the frictional strength of both the sediments and serpentinized mantle (friction angle 1 to 15, or static friction coefficient 0.017 to 0.27) to control the amount of frictional coupling between the plates. With plastic strain weakening in the lithosphere, our numerical models can attain stable subduction geometry over millions of years. We find that the frictional strength of the sediments and serpentinized peridotite exerts the largest control on the dip angle of the subduction interface at seismogenic depths. In the case of low sediment and serpentinite friction, the subduction interface has a shallow dip, while the subduction zone develops an accretionary prism, a broad forearc high, a deep forearc basin, and a shallow trench. In the high friction case, the subduction interface is steep, the trench is deeper, and the accretionary prism, forearc high and basin are all absent. The resultant free-air gravity and topographic signature of these subduction zone models are consistent with observations. We believe that the low-friction model produces a geometry and forearc structure similar to that of accretionary margins. Conversely, models with high friction angles in sediments and serpentinite develop characteristics of an erosional convergent margin. We find that the strength of the subduction interface is critical in controlling the amount of coupling at the seismogenic zone and perhaps ultimately the size of the largest earthquakes at subduction zones. © 2012. American Geophysical Union. All Rights Reserved.
|Original language||English (US)|
|Number of pages||1|
|Journal||Geochemistry, Geophysics, Geosystems|
|State||Published - Oct 9 2012|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): US00003
Acknowledgements: We would like to thank Taras Gerya, an anonymous reviewer, the Associate Editor, and the Editor, whose constructive reviews greatly improve this manuscript. HVA received support from the U.S. NSF MARGINS program under grant OCE0405556. LLL and ET received funding from the U.S. NSF Continental Dynamics program under grant EAR0607588 and from KAUST under grant US00003. AH was supported as part of the Eurohorcs/ESF-European Young Investigators Awards Scheme (resp. Francesca Funiciello), by funds from the National Research Council of Italy and other National Funding Agencies participating in the 3rd Memorandum of Understanding, as well as from the EC Sixth Framework Programme. This is UTIG contribution 2491.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.