  The energy dependence of "secondary" neutrinos from the process
nutau->tau->numubar->mubar for two input tau neutrino fluxes (F^0_nu ~ 1/E_nu
and 1/E_nu^2), assumed to have been produced via neutrino oscillations from
extragalactic sources, is evaluated to assess the impact of secondary neutrinos
on the upward muon rates in a km^3 detector. We show that the secondard fluxes
are considerably suppressed for the steeper flux, and even for fluxes ~ 1/E_nu,
the secondary flux will be difficult to observe experimentally.
