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Stress-strength relationship in the lithosphere during continental collision

Stefan M. Schmalholz, Boris J. P. Kaus and Jean-Pierre Burg
Stress-strength relationship in the lithosphere during continental collision
Geology (Boulder) (September 2009) 37 (9): 775-778

Abstract

Lithospheric strength profiles generated for a shortening continental lithosphere generally predict excessively high differential stresses in the sub-Moho continental mantle; this seems inconsistent with the relative scarcity of earthquakes at this depth. This inconsistency was put forward as evidence for weak mantle rheology. However, this argument implicitly assumes that strength envelopes are valid in actively deforming regions. We test this assumption on two end-member model lithospheres having identical upper crustal rheologies, but with (1) a weak lower crust and strong mantle, and (2) a strong lower crust and weak mantle. For this purpose, we compare one-dimensional (1-D) with 2-D visco-elastoplastic numerical models of continental shortening. The 2-D models show that strongly heterogeneous deformation typically follows initially homogeneous deformation. Lithospheric-scale buckle folds and shear zones result in strain rate variations of as much as three orders of magnitude. Differential stresses in the upper crust are close to yield, as predicted by 1-D models. Stresses in deeper lithospheric regions, however, are significantly smaller than in 1-D models, especially in actively deforming regions. Systematic numerical simulations as a function of temperature and deformation rate reveal that 1-D models are reliable in hot and/or slowly deforming lithospheres only. The relative scarcity of earthquakes at mantle levels should thus be interpreted as an intrinsic consequence of strong lithospheric deformation rather than as evidence for a weak upper mantle.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 37
Serial Issue: 9
Title: Stress-strength relationship in the lithosphere during continental collision
Affiliation: ETH Zurich, Department of Earth Sciences, Zurich, Switzerland
Pages: 775-778
Published: 200909
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 31
Accession Number: 2009-088589
Categories: Solid-earth geophysicsEngineering geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, sects.
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200948
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