For this study we use data acquired by the European Space Agency satellites ERS-1 and ERS-2 between 1992 and 2001. The North Bay region is covered in its entirety by a single descending track scene (track 342, frame 2835), and in total 30 useable images were acquired over this frame in the study interval. Permanent scatterers (PS) were identified using the method of Ferretti et al. (2001) , and a best linear line-of-sight (LOS) velocity estimated for each. In total, 71000 PS were identified (Figure 2.39a).

On a regional scale, the velocity field obtained by PS-InSAR shows the deformation due to accumulation of strain on the major strike-slip faults. In Figure 2.39a this is represented by a color change from red to blue from west to east, signifying an eastward increase in velocity of $\sim 10$ mm/yr towards the satellite. This is consistent with right-lateral shear across the fault system (e.g. Bürgmann et al., 2006). More locally, steps in LOS velocity across faults represent shallow creep on those structures. We can identify such features for the Hayward and, we argue below, Rodgers Creek faults.

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