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| Titel |
Characterization of Fault Roughness at Various Scales: Implications of Three-Dimensional High Resolution Topography Measurements |
| VerfasserIn |
T. Candela, F. Renard, M. Bouchon, A. Brouste, D. Marsan, J. Schmittbuhl, C. Voisin |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250020600
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| Zusammenfassung |
| Accurate description of the topography of active faults surfaces represents an important
geophysical issue because this topography is strongly related to the stress distribution along
fault planes, and therefore to processes involved in earthquake nucleation, propagation, and
arrest.
In the present study, we investigate the scaling properties, including possible anisotropy
properties of several outcrops of two fault surfaces (Vuache strike-slip fault, France, and
Magnola normal fault, Italy) in limestones. At the field scale, recent Light Detection And
Ranging (LIDAR) apparatus are used to acquire digital elevation models of the fault
roughness over surfaces of 0.25 m2 to 600 m2 with a height resolution ranging from 0.5 mm
to 20 mm. At the laboratory scale, the 3D geometry is obtained on two slip planes, using a
laser profilometer with a spatial resolution of 20 μm and a height resolution less than 1
μm.
The scaling properties of these surfaces are measured using six different signal processing
techniques. To investigate quantitatively the reliability and accuracy of the different methods,
we generated synthetic self-affine surfaces with azimuthal variation of the scaling exponent,
similar to what is observed for natural fault surfaces. The accuracy of the signal processing
techniques is assessed in terms of the difference between an “input” self-affine
exponent used for the synthetic construction and an “output” exponent recovered by
those different methods. Two kinds of biases are identified: artifacts inherent to
data acquisition and intrinsic errors of the methods themselves. In the latter case,
the statistical results of our parametric study provide a quantitative estimate of
the dependence of the accuracy with system size and directional morphological
anisotropy.
Finally, using the most reliable techniques, we characterized the topography
perpendicular to the slip direction that displays a similar scaling exponent H⊥ = 0.8 at all
scales. However, our analysis indicates that for the Magnola fault surface the scaling
roughness exponent parallel to the mechanical striation is identical at large and small scales
H∕∕ = 0.6 - 0.7 whereas for the Vuache fault surface it is characterized by two different
self-affine regimes at laboratory and field scales. We interpret this cross-over length scale as a
witness of different mechanical processes responsible for the creation of fault topography at
different spatial scales. |
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