Astronomy and Astrophysics – Astronomy
Scientific paper
Feb 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000geoji.140..399a&link_type=abstract
Geophysical Journal International, Volume 140, Issue 2, pp. 399-409.
Astronomy and Astrophysics
Astronomy
21
Creep, Finite Element Method, Lithosphere, Lithosphere Deformation, Rheology, Strain Rate
Scientific paper
We have generated an elastoviscoplastic (EVP) rheological model of the lithosphere with an extended Maxwell model containing (in series) a linear elastic component, a creep component based on a flow law for dislocation creep in olivine, and a frictional component simulating Drucker-Prager plasticity based on Byerlee's rule. Finite element analyses for topographic loading of this oceanic lithosphere were carried out with two separate final loads (100 and 150MPa) that were reached by four different load growth times (0, 0.1, 1, 10Myr). Our results for the stress state and deformation of loaded lithosphere at 41.7Myr into the model run are compared to results generated by the mechanical response of a time-independent elastic-perfectly plastic (EP) lithosphere, using a moment-curvature relationship based on the constant strain-rate yield strength envelope (YSE) and adopting a strain-rate representative of the EVP solution at 41.7Myr. With identical flexural loading and material parameters, the deflection profiles of the EVP and EP solutions are quite similar, but it is unclear how the EP strain rate could be selected a priori without guidance from the EVP solution. For example, this uncertainty translates to about a 5 per cent error per decade of strain rate in the temperature gradient obtained by matching maximum moment and curvature in our EP models. The stress distributions of the time-dependent EVP model show deviations from the EP model (as defined by the YSE and an elastic core) in crystal plastic (macroscopically continuous dislocation creep) regions, where we observe vertical, lateral and temporal variations in the strain rate. At times much greater than the load growth time, the stress distribution in the lithosphere is independent of the loading rate and depends on the load magnitude only in that portion of the lithosphere that yields to frictional slip. After loading ceases, residual creep zones develop (in the vicinity of the brittle-plastic transition and the elastic-creep transition), driven by high stress in these regions.
Albert Richard A.
Brown David C.
Dombard Andrew J.
Phillips Roger J.
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