Using a quasi-static three dimensional fault model which accounts for long range elastic interactions, we examine the influence of spatial heterogeneities of frictional strength on the slip distribution along a creeping fault. Slip fluctuates spatially because of pinning on local asperities. We show that three regimes of slip correlations exist. The first regime results in a uniform slip as in an homogeneous medium. On the contrary, slip in the second regime highly fluctuates and is controlled by heterogeneities of frictional strength. The third regime is intermediate and develops areas of high slip that are much bigger than the local asperity size (self-affine properties of the slip distribution). This particular regime illustrates the possible misinterpretation of low frequency slip data (e.g. interferometric and GPS data) in terms of structural or compositional properties along the fault. ¿ 2001 American Geophysical Union