Multiple faults in ductile simple shear: Analogue models of flanking structure systems

Author(s)
Ulrike Exner, Bernhard Grasemann, Neil S. Mancktelow
Abstract

Rotational behaviour and deformation around multiple faults was investigated in analogue experiments using a linear viscous matrix material under simple shear boundary conditions. Previous analogue and numerical studies have shown that, for single faults, characteristic deformation geometries are produced in initially straight marker lines parallel to the shear zone boundary (flanking structures). Observations from several natural shear zones suggest that not only single faults, but often several parallel or conjugate fault planes are subjected to progressive shear resulting in distinctive deflection geometries. If the distance between faults is on the order of their length, or less, then the perturbation flow fields interfere and coalescence, and finite deflection structures develop that are distinctly different from those around single fractures. In particular, coeval contractional and extensional geometries may develop across conjugate faults, although for bulk simple shear the total length of marker lines parallel to the shear zone boundary cannot change. This advises caution in inferring shear-zone parallel contraction or extension from secondary slip surfaces. In contrast to single flanking structures, conjugate flanking structure systems occurring in natural shear zones are reliable shear sense indicators due to their triclinic symmetry. Œ The Geological Society of London 2006.

Organisation(s)
Department of Geology
External organisation(s)
Eidgenössische Technische Hochschule Zürich
Journal
Journal of Structural Geology
Volume
26
Pages
2191-2201
No. of pages
11
ISSN
0191-8141
Publication date
2006
Peer reviewed
Yes
Austrian Fields of Science 2012
1051 Geology, Mineralogy
Portal url
https://ucrisportal.univie.ac.at/en/publications/0e301882-88e5-4638-882b-e28e353297aa