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| Titel |
Conditions for the activation of splay faults in accretionary prisms: application to Nankai |
| VerfasserIn |
Adeline Pons, 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 |
250053598
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| Zusammenfassung |
| One key issue to predict the activation of splay faults such as in Nankai, is to understand the
role of the distribution in pressure and frictional properties, within the weak décollement and
in the inherited faults, on the stability of the prism.
To this end, a general procedure is proposed to extend classical Dahlen’s theory to wedges
of arbitrary topography and composed of heterogeneous rocks. Our approach relies on the
kinematic approach of limit analysis (e.g. Cubas et al., 2008) extended here for
fluid-saturared rocks. The procedure is validated by comparing our stability predictions for a
triangular wedge with Dahlen’s criterion. Stable wedges correspond to the complete
activation of the décollement, so that deformation is towards the external region. This
failure mode corresponds to super-critical conditions. For sub-critical conditions, the
failure mode is composed of the partial activation of the décollement in the internal
region to the point where the ramp and the back-thrust are taking their common
root.
The application to the Kumano transect of Nankai is based on a prototype with a
topography inspired by the observations of Park et al., 2002. The décollement is partionned
into an internal and an external section where the friction angles and the pressure ratios differ,
as proposed by Kimura (2007). The first failure mechanism is one where the décollement is
activated over its entire length. The second failure mechanism sees slip on a partial of the
décollement only and activation of the splay fault. The fluid pressure ratios in the internal and
the external part of the décollement (λI and λE) which warrant the dominance of the first
or second mechanism are then presented. The sensitivity of these predictions to
the frictional properties and pressure ratio of the splay fault is finally explored. |
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