HR: 0800h
AN: T41F-1278    [Abstracts]
TI: Stable and Critical Noncohesive Coulomb Wedges: Exact Elastic Solutions
AU: * Wang, K
EM: kwang@nrcan.gc.ca
AF: Pacific Geoscience Centre, Geological Survey of Canada, 9860 W Sannich Rd, Sidney, BC V8L 4B2 Canada
AU: Hu, Y
EM: yhu@nrcan.gc.ca
AF: University of Victoria, School of Earth and Ocean Sciences, Victoria, BC V8W 3P6 Canada
AB: The theory of critically tapered Coulomb wedge has been successfully applied to model active fold-and-thrust belts or submarine accretionary prisms. Brittle mountain building is episodic in nature, controlled by changes in basal friction, erosion and sedimentation, and hydrogeology. Sediment accretion may be modulated by great subduction earthquakes. Between deformation episodes and/or during transition between compressional and extensional tectonics, the Coulomb wedges are stable (i.e., supercritical), to which the critical taper theory does not apply. In this work, we provide an exact elastic solution for stable wedges based on Airy stress functions. The stress equilibrium equation and definition of basal friction and basal and internal pore fluid pressure ratios are exactly the same as those used for Dahlen's [1984] exact solution for critical noncohesive Coulomb wedges, but internal friction $\mu$ becomes irrelevant. Given elastic - perfectly Coulomb-plastic rheology, for stresses in a wedge on the verge of Coulomb failure there must co-exist a critical taper solution involving $\mu$ and a unique equivalent elastic solution not involving $\mu$. Our elastic solution precisely reduces to Dahlen's critical taper solution for critical conditions. For stable conditions, normal stress perpendicular to the surface slope $\sigma_z$ and shear stress $\tau_{xz}$ are identical with those in a critical taper, but the slope-parallel normal stress is different. The elastic solution is also generally applicable to purely elastic wedges and useful for modeling geodetic observations. A stable noncohesive Coulomb wedge differs from a general elastic wedge in that its upper and lower surfaces stay at zero curvature during loading. Dahlen, F.A. (1984), Noncohesive critical Coulomb wedges: An exact solution, JGR, 89, 10,125-10,133.
DE: 8020 Mechanics
DE: 8150 Plate boundary--general (3040)
DE: 8159 Rheology--crust and lithosphere
DE: 8164 Stresses--crust and lithosphere
DE: 1242 Seismic deformations (7205)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting