  We present a measurement of the high-energy astrophysical muon-neutrino flux
with the IceCube Neutrino Observatory. The measurement uses a high-purity
selection of ~650k neutrino-induced muon tracks from the Northern celestial
hemisphere, corresponding to 9.5 years of experimental data. With respect to
previous publications, the measurement is improved by the increased size of the
event sample and the extended model testing beyond simple power-law hypotheses.
An updated treatment of systematic uncertainties and atmospheric background
fluxes has been implemented based on recent models. The best-fit single
power-law parameterization for the astrophysical energy spectrum results in a
normalization of $\phi_{\mathrm{@100TeV}}^{\nu_\mu+\bar{\nu}_\mu} =
1.44_{-0.26}^{+0.25} \times
10^{-18}\,\mathrm{GeV}^{-1}\mathrm{cm}^{-2}\mathrm{s}^{-1}\mathrm{sr}^{-1}$ and
a spectral index $\gamma_{\mathrm{SPL}} = 2.37_{-0.09}^{+0.09}$, constrained in
the energy range from $15\,\mathrm{TeV}$ to $5\,\mathrm{PeV}$. The model tests
include a single power law with a spectral cutoff at high energies, a
log-parabola model, several source-class specific flux predictions from the
literature and a model-independent spectral unfolding. The data is well
consistent with a single power law hypothesis, however, spectra with softening
above one PeV are statistically more favorable at a two sigma level.
