HR: 0800h
AN: T11B-0363    [Abstracts]
TI: Mechanics of thrust fault development within accretionary wedges.
AU: * Del Castello, M
EM: mariod@geo.umass.edu
AF: University of Massachusetts, Geosciences Department 611 North Pleasant Street, Amherst, MA 01003 United States
AU: Cooke, M
EM: cooke@geo.umass.edu
AF: University of Massachusetts, Geosciences Department 611 North Pleasant Street, Amherst, MA 01003 United States
AB: Sandbox models of accretionary wedge development have demonstrated that thrust fault systems growth is episodic with periods of wedge thickening accommodated by slip along faults within the wedge interspersed with periods of wedge lengthen via growth of new thrust faults in front of the wedge. Many factors contribute to the shift from wedge thickening to development of a new frontal thrust including, 1) steepening of faults within the wedge, 2) greater lithostatic compression across wedge faults as the topography is uplifted and 3) strain hardening of the wedge material. We seek to better understanding the contribution of each of these processes to the growth of a new frontal thrust by modeling the incipient thrust development within two-dimensional Boundary Element Method (BEM) models. Numerical models have benefits over physical models because the parameters can be readily altered in order to isolate the contributing processes to accretionary thrust mechanics. Rather than simulating the complete development of the accretionary wedge, our models simulate a snapshot of time at the initiation of the new frontal thrust. We systematically vary several model parameters in order to assess the role of each in the transition from wedge thickening to new thrust growth. Varied parameters include basal fault friction coefficient, wedge fault coefficient of friction, steepness of wedge faults, topography and sand compliance. The new thrust fault is expected to develop where the slip gradient on the basal detachment is sufficiently large to produce regions of large strain energy density. The development of the new thrust fault is shown to reduce the external work on the system, by reducing internal strain energy even while increasing frictional work and work against gravity.
DE: 8020 Mechanics, theory, and modeling
DE: 8108 Continental tectonics: compressional
DE: 8118 Dynamics and mechanics of faulting (8004)
SC: Tectonophysics [T]
MN: Fall Meeting 2005