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| Titel |
Thrusting sequences by the maximum strength theorem coupled to erosion laws |
| VerfasserIn |
Baptiste Mary, Bertrand Maillot, Yves Leroy |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250054757
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| Zusammenfassung |
| The numerical modelling of shallow tectonic structures meets challenges of two types: first,
assumptions must be made on the values of complex rheological parameters (elasticity,
plasticity criterion, plastic flow rule) that are usually only measured in the lab., therefore at
far shorter time and space scales; second, the transition from a localised shear deformation in
a band to a discontinuity sensu stricto, and the accumulation of large slip on the
discontinuities are still difficult to implement in computational tools. These difficulties are
avoided in our approach thanks to two simplifications. First, the rocks are solely described by
their density, their rupture criterion (e.g. Coulomb criterion), and slip-weakening (drop in
friction angle once failure is detected). Second, the deformation is assumed to be entirely
accomodated by slip along faults between rigid blocks (as in most kinematic models of
fault-related folding). Given a tectonic forcing, the maximum strength theorem – part of
limit analysis – provides the optimal positions, lengths and dips of the faults. The
application of the theorem at each step of shortening provides an extremely efficient,
semi-analytic method for predicting thrusting sequences above a décollement in 2D vertical
cross-sections. We show here that the coupling of this new method to 1D and 1.5D erosion
laws provides a numerical tool to predict the actual shape and the development of
mountain belts. We examine in particular the relations between slip-weakening on
thrusts, lifetime of thrusts, thickness of thrusted units, and erosion, and compare our
results to analog experiments, and structures in the Western Foothills of Taiwan. The
proposed method being semi-analytical, it is possible to explore fully the parametric
space and thus to perform a complete quantitative comparison, deducing likely
frictional history of thrusts from their observed geometry and the surface topography. |
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