SIMPLIFIED ANALYSIS OF HORIZONTAL STRESSES IN A BUTTRESSED FOREARC SLIVER AT AN OBLIQUE SUBDUCTION ZONE

摘要

Forearc slivers are commonly present at obliquely convergent margins. Such slivers are often buttressed at their leading edges, but no quantitative model of the buttress effect exists. I consider the horizontal stresses in a buttressed sliver using a simple plan-view two-dimensional elastic model. The driving force created by the subducting plate is approximated by a body force in the direction of plate convergence. An Airy stress function solution relates the stress field to the boundary and body forces that allows the relative importance of different forces driving and resisting the sliver to be evaluated. Oblique subduction can easily cause are-parallel compression in the buttressed sliver, especially near the leading edge, because the are-parallel component of the driving force by the subducting plate is integrated over a much larger distance than its are-normal component. For the Southwest Kuril are, the stress field predicted by the simple model agrees with that inferred from geological structures. It is possible that the model can also explain the stress field of the Cascadia forearc as constrained by earthquake focal mechanisms and in situ stress measurements. [References: 24]