  The decay pattern of aftershocks in the so-called 'coherent-noise' models [M.
E. J. Newman and K. Sneppen, Phys. Rev. E54, 6226 (1996)] is studied in detail.
Analytical and numerical results show that the probability to find a large
event at time $t$ after an initial major event decreases as $t^{-\tau}$ for
small $t$, with the exponent $\tau$ ranging from 0 to values well above 1. This
is in contrast to Sneppen und Newman, who stated that the exponent is about 1,
independent of the microscopic details of the simulation. Numerical simulations
of an extended model [C. Wilke, T. Martinetz, Phys. Rev. E56, 7128 (1997)] show
that the power-law is only a generic feature of the original dynamics and does
not necessarily appear in a more general context. Finally, the implications of
the results to the modeling of earthquakes are discussed.
