HR: 10:35h
AN: S32B-02    [Abstracts]
TI: Length Scaling of Shear Zones at the Frictional-Viscous Transition (FVT)
AU: * Schrank, C E
EM: schrank@geology.utoronto.ca
AF: Department of Geology, University of Toronto, Earth Sciences Centre, 22 Russell Street, Toronto, ON M5S 3B1 Canada
AU: Handy, M R
EM: mhandy@zedat.fu-berlin.de
AF: Department of Earth Sciences, Freie Universitaet Berlin, Malteserstrasse 74-100, Berlin, 12249 Germany
AU: Fusseis, F
EM: fusseis@zedat.fu-berlin.de
AF: Department of Earth Sciences, Freie Universitaet Berlin, Malteserstrasse 74-100, Berlin, 12249 Germany
AB: We present a new method for determining the characteristic length scales of strain localization in crustal scale shear zones. This entails determining two parameters that describe the degree of strain heterogeneity in natural shear zones: (1) the strain localization factor, Lf_RA, defined as the ratio of the shear zone area to a chosen reference area, A_RA, and (2) the relative localization intensity, I_loc, a function of the ratio of the mean shear strain to the maximum shear strain measured in a transect of the shear zone. A_RA is a geometric homogenization scale determined from autocorrelation functions (ACF) of 2-D images (thin sections, foliation maps and aerial photographs) of shear zone networks on different scales that formed during a single deformational event. When applied to shear zones from a well exposed segment of the frictional-to-viscous transition (FVT) in NE Spain, we found that maxima in Lf_RA on the mm, cm, m and km scales coincided with the length scales of existing mineralogical and lithological heterogeneities. On any of these characteristic length scales, I_loc increased both along and across the length of the shear zones, suggesting that the shear zones weakening as a function of time and strain. This is consistent with structural evidence for progressive weakening of the crust on the characteristic length scales of strain heterogeneity.
DE: 1236 Rheology of the lithosphere and mantle (7218, 8160)
DE: 7205 Continental crust (1219)
DE: 8012 High strain deformation zones
SC: Seismology [S]
MN: Fall Meeting 2005