The effect of long term coupling in subduction zones on forearc topography is studied using a 2-dimensional finite element model. A curved fault, representing the interface between subducting slab and overriding plate, has been incorporated into a model with an elastic crustal layer, a viscoelastic upper mantle, an initial topography, and an effective coefficient of friction on the fault. We assume that traction arising from friction is one of the stresses acting on topography. For various friction coefficients, the change of topography after some equilibration time is computed with specific geometry and kinematic boundary conditions for three subduction zones: northern Chile, northern Japan, and Tonga. While the intrinsic coefficient of friction for small rock samples is high (&mgr;~0.6--0.8), the observed topography of forearc regions are inconsistent with an effective friction coefficient larger than 0.2.¿ 1997 American Geophysical Union