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| Titel |
Stress field sensitivity analysis in a sedimentary sequence of the Alpine foreland, northern Switzerland |
| VerfasserIn |
T. Hergert, O. Heidbach, K. Reiter, S. B. Giger, P. Marschall |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1869-9510
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| Digitales Dokument |
URL |
| Erschienen |
In: Solid Earth ; 6, no. 2 ; Nr. 6, no. 2 (2015-05-21), S.533-552 |
| Datensatznummer |
250115449
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| Publikation (Nr.) |
 copernicus.org/se-6-533-2015.pdf |
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| Zusammenfassung |
| The stress field at depth is a relevant parameter for the design of
subsurface constructions and reservoir management. Yet the distortion of the
regional stress field due to local-scale features such as sedimentary and
tectonic structures or topography is often poorly constrained. We conduct a
stress sensitivity analysis using 3-D numerical geomechanical modelling with
an elasto-plastic material law to explore the impact of such site-specific
features on the stress field in a sedimentary sequence of the Swiss Alpine
foreland. The model's dimensions are 14 × 14 × 3 km3
and it contains 10 units with different mechanical properties, intersected
by two regional fault zones. An initial stress state is established
involving a semi-empirical relationship between the ratio of horizontal to
vertical stress and the overconsolidation ratio of argillaceous sediments.
The model results indicate that local topography can affect the stress field
significantly to depths greater than the relief contrasts at the surface,
especially in conjunction with horizontal tectonic loading. The complexity
and frictional properties of faults are also relevant. The greatest
variability of the stress field arises across the different sedimentary
units. Stress magnitudes and stress anisotropy are much larger in stiffer
formations such as massive limestones than in softer argillaceous
formations. The stiffer formations essentially carry the load of the
far-field forces and are therefore more sensitive to changes of the boundary
conditions. This general characteristic of stress distribution in the stiff
and soft formations is broadly maintained also with progressive loading
towards the plastic limit. The stress field in argillaceous sediments within
a stack of formations with strongly contrasting mechanical properties like
in the Alpine foreland appears to be relatively insensitive to changes in
the tectonic boundary conditions and is largely controlled by the maximum
stiffness contrast with respect to the load-bearing formations. |
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