HR: 13:40h
AN: T43E-01    [Abstracts]
TI: Mechanics of Clay Smear Formation Along Faults
AU: * Clausen, O R
EM: ole.r.clausen@geo.au.sk
AF: Department of Earth Sciences University of Aarhus, Høegh-Guldbergs Gade 2, Aarhus, DK8000, Denmark
AU: Egholm, D L
EM: david@geo.au.dk
AF: Department of Earth Sciences University of Aarhus, Høegh-Guldbergs Gade 2, Aarhus, DK8000, Denmark
AU: Korstgård, J A
EM: john.korstgard@geo.au.dk
AF: Department of Earth Sciences University of Aarhus, Høegh-Guldbergs Gade 2, Aarhus, DK8000, Denmark
AB: Clay- or shale-rich smears developed along faults in interlayered clay and sand sediments are known to significantly change the hydraulic properties of the formation. Predicting the volume of clay or shale smeared along faults is therefore important for estimating the fluid connectivity in groundwater and hydrocarbon systems as well for the integrity of artificially sequestered CO₂ reservoirs. Here we show how fault smears develop spontaneously in deforming layered systems, where the interlayered clay and sand have varying friction coefficients, and we present a quantitative dynamic model for this behavior. The model is based on Mohr-Coulomb failure theory, and with discrete element computations we demonstrate, how the model framework can be used for predicting the fault smear potential from soil friction angles and layer thicknesses. The modeled results show how friction angle variations not only control the amount of clay available for smearing, but also the along-bed offsetting of the fault planes - a phenomenon often recognized in outcrops. The modeled results are compared to observations of both the external and internal geometry of naturally formed clay smears in order to prove the validity of the dynamic model.
DE: 0560 Numerical solutions (4255)
DE: 8004 Dynamics and mechanics of faulting (8118)
DE: 8020 Mechanics, theory, and modeling
DE: 8034 Rheology and friction of fault zones (8163)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting