[1] Convergent margins with oblique subduction commonly include a fore-arc sliver, a portion of the overlying plate bounded by the trench and a major strike-slip fault system. It has long been noted that relative plate motion near the deformation front, as indicated by earthquake focal mechanisms, is generally closer to margin-normal than would be expected from overall relative plate motion. This results from sliver motion as well as from shear within the fore arc. We carry out some simple calculations to determine how the rate of sliver motion should vary with plate convergence obliquity. We find that the results are related to rheology but that the measurement of sliver rates at natural fore arcs is unlikely to yield real insight into physical properties; even for very simple models; the system is too complicated and its relation to rheology is not unique. The proportion of oblique convergence taken up by sliver motion in simple tabletop experiments depends on the rate of slip and the smoothing of asperities. Similarities in taper and style of strain between frontal wedges forming with and without slivers suggest that structural observations of exhumed accretionary wedges are unlikely to allow geologists to draw definitive conclusions about the degree of obliquity of relative plate motion at the time when the wedges were formed and in some cases not even whether or not a sliver plate was present at the time of deformation. Citation: Haq, S. S. B., and D. M. Davis (2010), Mechanics of fore-arc slivers: Insights from simple analog models, Tectonics, 29, TC5015,

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The Cenozoic landscape evolution in southwestern North America is ascribed to crustal isostasy, dynamic topography, or lithosphere tectonics, but their relative contributions remain controversial. Here we reconstruct landscape history since the late Eocene by investigating the interplay between mantle convection, lithosphere dynamics, climate, and surface processes using fully coupled four-dimensional numerical models. Our quantified depth-dependent strain rate and stress history within the lithosphere, under the influence of gravitational collapse and sub-lithospheric mantle flow, show that high gravitational potential energy of a mountain chain relative to a lower Colorado Plateau can explain extension directions and stress magnitudes in the belt of metamorphic core complexes during topographic collapse. Profound lithospheric weakening through heating and partial melting, following slab rollback, promoted this extensional collapse. Landscape evolution guided northeast drainage onto the Colorado Plateau during the late Eocene-late Oligocene, south-southwest drainage reversal during the late Oligocene-middle Miocene, and southwest drainage following the late Miocene.

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