Plate subduction causes compression of the continental crust in Northeast (NE) Japan but not in Southwest (SW) Japan. We propose that the different effects are both consistent with weak subduction faults, of which the static shear stress is described using an effective coefficient of friction &mgr;'. Stresses in the overriding plate are controlled by two competing factors, the plate coupling force, inducing compression, and the gravitational force, inducing tension. In cold subduction zones such as NE Japan the frictionally coupled portion of the thrust fault is wider and extends to a greater depth. Thus even a low &mgr;' can give rise to a large total plate coupling force and hence compression in the upper plate. Using a model of two converging plates in frictional contact, we find that a &mgr;' of 0.03 explains the first-order stresses of both NE and SW Japan. ¿ 1999 American Geophysical Union