Figure 7. Time-dependent deformation at strike-slip faults.

Interseismic and postseismic strain rates for four strike-slip faults where data are available before and after a major earthquake⁷⁴,¹⁰⁵,¹⁰⁸,¹²⁵,¹²⁶,¹²⁷,¹²⁸. Strain rates in units of microstrain per year and are normalized by the long-term slip rate of the fault. Time is normalized by the average inter-event time for the fault. The curved lines show model predictions from a simple viscoelastic coupling model, with an average slip rate of 1 mm per year, in which repeating earthquakes occur above a viscoelastic substrate. The controlling non-dimensional parameter, τ₀, is the ratio of Maxwell relaxation time to inter-event time; τ₀ values of 0.001/0.01/0.1/1 correspond to a viscosities of ∼10¹⁷/10¹⁸/10¹⁹/10²⁰ Pa s for typical inter-event times.