Estimating friction in normal fault systems of the Basin and Range province and examining its geological context

The life cycle of a fault following initiation is governed in part by the reshear criterion, of which rock surface friction is the critical factor limiting the dip of a fault at its death. Using structural restorations where the initial and final dips of faults can be ascertained, the coefficient of rock surface friction is calculated for well-characterized extended locales (n = 20) in the Basin and Range province, many with multiple fault generations (n = 34). The calculated values exhibit a considerably wider range (0.19-1.33) than previously reported. The amount of tilting associated with each fault generation is compared with eight characteristics (mean slip magnitude, tilting per unit of slip, fault spacing, percentage extension, absence or presence and composition of magmatism, duration of extension, timing of extension and strain rate). No statistically strong correlation was found with any of the examined characteristics, although tentative linkages were noted with percentage extension, strain rate and mean slip magnitude from weighted regression analysis. These results are consistent with normal faults behaving as non-linear systems, with friction being an emergent property.