Slip correlations on a creeping fault

Using a quasi-static three dimensional fault model which accounts for long range elastic interactions, we examine the influence of spatial heterogenei ties 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 s econd regime highly fluctuates and is controlled by heterogeneities of fric tional strength. The third regime is intermediate and develops areas of hig h sip that are much bigger than the local asperity size (self-affine proper ties of the slip distribution). This particular regime illustrates the poss ible misinterpretation of low frequency slip data (e.g. interferometric and GPS data) in terms of structural or compositional properties along the fau lt.