HR: 0800h
AN: T31A-0285    [Abstracts]
TI: Influence of plate boundary geometry on the stress regime in an arc/back-arc setting
AU: * Boutelier, D A
EM: boutelier@geology.utoronto.ca
AF: University of Toronto, Dept. Geology, 22 Russell Street, Toronto, ON M5S 3B1, Canada
AU: Cruden, A R
EM: cruden@geology.utoronto.ca
AF: University of Toronto, Dept. Geology, 22 Russell Street, Toronto, ON M5S 3B1, Canada
AB: The influence of convergent plate boundary curvature on the stress distribution in an overriding plate is explored using a combination of analogue and numerical modeling techniques. Horizontal components of normal and shear stresses generated by subduction are imposed on the side of the numerical model representing a curved in-plane subduction zone. Normal stress corresponding to compressive oceanic subduction produces tensile trench-parallel stress in a lobe situated at the intersection of the plate boundary and symmetry axis of the curvature. This situation favors the development of strike-slip faults allowing horizontal extrusion of the overriding lithosphere. The horizontal component of the shear stress comprises a trench-normal component whose action resembles that of the normal stress, and a trench-parallel component that acts in the opposite direction. The trench-parallel stress exerted by subduction along both sides of a convex plate boundary produces along-strike compression near the intersection of the curvature symmetry axis and interplate zone. This lateral compression suggests that the least compressive stress is vertical, which promotes vertical thickening of the overriding plate. The role of the obliquity angle in generating lateral drag is further investigated using analogue modeling technique, while the balance between normal and shear stress is explored with the numerical technique. For compressive oceanic subduction and continental subduction, the normal stress is expected to be far greater than the shear stress and a convex geometry of the plate boundary promotes horizontal extrusion of the overriding plate. However, in specific situations, such as when the trench is starved of lubricating sediments, the shear stress magnitude may be raised thus enhancing the thickening of the arc/back-arc domain. This corresponds, for example, to the situation in the Central Andes where faster and greater crustal thickening of the Altiplano-Puna plateau is situated near the symmetry axis of the plate boundary.
DE: 8104 Continental margins: convergent
DE: 8108 Continental tectonics: compressional
DE: 8111 Continental tectonics: strike-slip and transform
DE: 8168 Stresses: general
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting