HR: 1330h
AN: T22B-0508    [PDF]
TI: Flexing is Not Stretching: An Analog Study of Flexure-Induced Fault Growth
AU: * Supak, S K
EM: supak@ldeo.columbia.edu
AF: Columbia University, Dept. of Civil Engineering, New York, NY 10027 United States
AU: * Supak, S K
EM: supak@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Box 1000, Palisades, NY 10964 United States
AU: Bohnenstiehl, D R
EM: del@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Box 1000, Palisades, NY 10964 United States
AU: Buck, W R
EM: buck@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Box 1000, Palisades, NY 10964 United States
AB: A thin (5 mm thick) plaster layer floating on a foam rubber substrate is bent and fractured in an analog model of extensional fault growth during lithospheric flexing. The size-frequency scaling of the resulting crack populations were analyzed. Unlike lithospheric stretching models, crack populations formed during these experiments indicate that length- and spacing- frequency distributions are not well described by a power-law model. Rather, these size-frequency data are better described by a negative exponential distribution. The absence of a power-law fault distribution reflects the preferential nucleation and growth of faults in association with stress maxima along the axis of the flexing plate. In contrast, the cracks formed in response to stretching evolve, due to elastic interaction during simultaneous growth, from an initially random distribution of nucleation points to form a self-similar network of fractures. The model predicts a non-power-law fault distribution for any area of moderate or large magnitude lithospheric flexure. The outer rise of trenches is an area of undisputed flexural faulting; however, in these environments, fault distributions have not yet been analyzed. A recent model for axial highs of fast-spreading ridges suggests that lithosphere is flexed significantly as it rafts away from ridge axes. Several studies of ocean floor fault populations near axial highs report non-power-law scaling, consistent with our analog model predictions for plate flexure.
DE: 3035 Midocean ridge processes
DE: 5114 Permeability and porosity
DE: 8010 Fractures and faults
DE: 8020 Mechanics
DE: 8120 Dynamics of lithosphere and mantle--general
SC: Tectonophysics [T]
MN: 2003 Fall Meeting