Earthquake sequences and populations

in dynamic fault models

Vertical strike-slip fault in elastic half space     Above:  A dynamic slip event.  Simulation with the "slip" version of the rate- and state- dependent friction.  Slip distribution is relative to a given value chosen by the plotting program.  The dynamic instability is preceded by a smoothly growing nucleation phase.  Last 15 seconds of the model earthquake.  The rupture propagates from the nucleation phase to the free surface and is then reflected downward.  Varations of final slip, visible clearly in the shallow zone, are associated with dynamic waves.    Above: Slip versus depth at 5 year interval in dynamic simulation of long history with the model relization of the preceding figure.  The response consists of quasi-periodic large events   Above: Slip versus depth at 2-year interval in dynamic simulation of long history with the ageing/slowness version of the rate- and state-dependent friction.  The creep process is active,  phas four steps, each to 10MPa offset from s_n at 4, 8, 12, and 16 km, and h= h*/4.  The response shows slip complexities associated with the strong heterogeneities of p.    Above: Slip versus depth at 0.3-year interval in dynamic simulation of an inherently discrete case h= 4h* with the slip version of friction. the creep process is disabled and  pis hydrostatic.  The results show a range of event sizes including small events.   Above:  Results for Ruina-Dieterich slip version of friction law, with h= 1.5 km and h*/h= 2:  Depth-averaged slip  versus distance xalong strike, shown at 5-year intervals.  The repeated distance in the model of Fig. 1 is 960 km.   Above:  Results for Dieterich-Ruina slowness, or ageing, version of friction law, with h = 0.75 km and h*/h = 3: Depth- averaged slip  versus distance x along strike, shown at 5 year intervals. The repeat distance in the model of the figure at the top of the page is 480 km. Note paucity of events with along-strike distance shorter than about 20 - 25 km.   Above:  Results for a model as in above figure: Slip d(x= 0, z, t) versus depth z, shown at 5 year intervals, at x = 0.   to James R. Rice page