HR: 09:30h
AN: T51E-07    [Abstracts]
TI: Scale-Dependent and Scale-Invariant Brittle Strain Regimes in the Earth's Crust
AU: * Soliva, R
EM: solivaroger@yahoo.fr
AF: Laboratoire Dynamique de la Lithosphere, Universite Montpellier II, Departement des Sciences de la Terre et de l'Environnement, Montpellier, 34000 France
AU: Schultz, R A
EM: schultz@mines.unr.edu
AF: Geomechanics Rock Fracture Group, Department of Geological Sciences and Engineering, University of Nevada, Reno, NV 89557-0138 United States
AB: Plate boundaries and rift zones are expressed in the brittle part of the crust as fault populations that have different characteristic geometries, i.e. distributed or localized brittle strain. These fault patterns are dependent on the occurrence of both long and short range stress interactions during the fault system development. Because the rheological properties of layered media can strongly influence this process, we analyse the main differences in fault populations that deform layered and homogeneous rocks. This leads to the recognition and characterization of (1) scale-invariant (or self-similar) and (2) scale-dependent (non fractal distributed strain) brittle strain regimes. We present a satellite image analysis of crustal scale fault populations from the Main Ethiopian Rift - Afar transition area of northeast Africa. This area exhibits exceptionally clear surface expression of the normal fault scarps over the whole topography of the region. Our analysis of the fault traces shows the occurrence of scale-dependent and scale-invariant strain regimes marked by a jump in the scale of fault segmentation. Our analysis suggests that rift border zone formation results from the development of scale-invariant regime allowing particularly large scale relay ramp formation and linkage (i.e. long range fault interactions). This strain localization along crustal scale faults overprints a non fractal distributed strain (i.e. short range and scale-dependent interactions), which is probably decoupled by rheological discontinuities within the brittle crust. The identification of scale-dependent and scale-invariant brittle strain regimes shows that crustal scale fault populations can develop by two different mechanisms and allows to quantitatively decipher plate break in extensional settings. It also allows discussing the presence and the depth of rheological discontinuity affecting the development of crustal-scale fault populations.
DE: 8004 Dynamics and mechanics of faulting (8118)
DE: 8010 Fractures and faults
DE: 8109 Continental tectonics: extensional (0905)
DE: 8163 Rheology and friction of fault zones (8034)
SC: Tectonophysics [T]
MN: Fall Meeting 2005