HR: 0800h
AN: T11A-0345    [Abstracts]
TI: Breaking up: Fault zone evolution during shear
AU: * Mair, K
EM: karen.mair@fys.uio.no
AF: Physics of Geological Processes, University of Oslo, PO Box 1048, Blindern, Oslo, 0316, Norway
AU: Abe, S
EM: s.abe@ged.rwth-aachen.de
AF: Geologie-Endogene Dynamik, RWTH Aachen, Lochnerstrasse 4-20, Aachen, 52056, Germany
AU: Bjork, T
EM: t.e.bjork@fys.uio.no
AF: Physics of Geological Processes, University of Oslo, PO Box 1048, Blindern, Oslo, 0316, Norway
AB: To better understand fault zone dynamics we need an improved understanding of the underlying micro- mechanics of the fault evolution process. Our basic data is gleaned from quantitative observations of structural fabrics associated with natural fault systems. However, such datasets generally record the final state of evolution, from which it is often difficult to discern the dynamic micro-scale processes involved, such as preferential fragmentation and strain partitioning, or the macro-mechanical behaviour of a fault. Laboratory experiments give valuable insights into links between microscale processes and macro-mechanical behaviour. Similarly, numerical simulations are very useful tools for visualising dynamic grain-scale interactions not readily visible from nature. Together these tools can help us identify and isolate first order parameters that are relevant for the faulting process. We present recent results from 3D simulations that implement realistic gouge evolution during shear. Our particle based simulation includes breakable elastic bonds between individual particles allowing fracture of aggregate grains that are composed of many bonded particles. With accumulated strain, aggregate grains fragment in different ways, gradually evolve in size and shape to produce a textural signature reminiscent of natural faults. We use a new image analysis tool to characterise grain shape and size distributions from thin sections obtained from natural and experimental fault rocks and are now applying this tool to 3D model results. This approach allows us to build on existing observations and permits closer investigation of dynamic bumping, grinding and fragmentation processes that may be operating in evolving fault zones.
DE: 7209 Earthquake dynamics (1242)
DE: 8010 Fractures and faults
DE: 8030 Microstructures
DE: 8034 Rheology and friction of fault zones (8163)
DE: 8118 Dynamics and mechanics of faulting (8004)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting