Crustal restraining bends along strike-slip faults are structurally complex systems comprised of multiple branching and closely spaced faults. With increasing loading on such systems, the faults reorganize as new faults grow and old faults are abandoned. In response to changes in the restraining bend geometry, slip rates, which are a primary input for seismic hazard models, at specific locations (sites) along faults can vary temporally (Chapter 1). We investigate how rheology and restraining bend geometry influence the restraining bend system evolution and fault slip-rate variability using scaled physical experiments. We simulate restraining bends within Earth’s upper crust using wet clay and dry sand as crustal analog materials. Rheological properties of the analog materials, such as strength and viscosity, (Chapters 2 & 4) as well as restraining bend angle (Chapter 3) impact restraining bend evolution. Like crustal rocks, the strength of viscoelastic wet clay decreases with decreasing strain rate. The complexity of the restraining bend systems that emerge within wet clay increases with decreasing loading rate. Comparisons between restraining bend models that use dry sand and wet clay show that a greater number of faults emerge within the weaker material (sand) compared to the stronger material (clay). With greater fault system reorganization, slip rates at sites along faults can exhibit larger and more frequent temporal variations (Chapters 3 & 4). The results of these projects can help guide interpretations of slip rate data along restraining bends hosted within a range of materials and settings. In addition to investigating temporal and spatial variations in slip rate within analog models, we develop a numerical method to constrain the three-dimensional distribution of current slip rates along complex fault systems (Chapter 5). Using boundary element models, we assess the performance of an inversion that utilizes subsurface stressing-rate tensors and surface velocities to estimate slip on the restraining bend along the San Andreas fault through the San Gorgonio Pass region. Simultaneous inversions of stressing-rate and surface velocity data could improve constraints on the spatial distribution of slip rates in regions like San Gorgonio Pass once a method to reliably estimate deviatoric stressing-rate tensors with magnitude exists.