  The recent discovery of extragalactic PeV neutrinos opens a new window to the
exploration of cosmic-ray accelerators. The observed PeV neutrino flux is close
to the Waxman-Bahcall upper bound implying that gamma-ray bursts (GRBs) may be
the source of ultra-high energy cosmic rays (UHECRs). Starting with the
assumption of the GRB-UHECR connection, we show using both analytical estimates
and numerical simulations that the observed neutrinos can originate at the jet
as a result of photopion interactions with the following implications: the
neutrino spectra are predicted to have a cutoff at energy $\le 10$ PeV; the
dissipation responsible for the GRB emission and cosmic-ray acceleration takes
place at distances $r_{\rm diss} \approx 3 \times 10^{11}-3 \times 10^{13} \
{\rm cm}$ from the central engine; the Thomson optical depth at the dissipation
region is $\tau_{\rm T} \sim 1$; the jet carries a substantial fraction of its
energy in the form of Poynting flux at the dissipation region, and has a
Lorentz factor $\Gamma \simeq 100-500$. The non-detection of $\sim$PeV
neutrinos coincident with GRBs will indicate that GRBs are either poor cosmic
accelerators or the dissipation takes place at small optical depths in the jet.
