  The neutrino oscillations in Earth matter introduce modulations in the
supernova neutrino spectra. These modulations can be exploited to identify the
presence of Earth effects on the spectra, which would enable us to put a limit
on the value of the neutrino mixing angle $\theta_{13}$ and to identify whether
the mass hierarchy is normal or inverted. We demonstrate how the Earth effects
can be identified at a single detector without prior assumptions about the
flavor-dependent source spectra, using the Fourier transform of the
``inverse-energy'' spectrum of the signal. We explore the factors affecting the
efficiency of this method, and find that the energy resolution of the detector
is the most crucial one. In particular, whereas water Cherenkov detectors may
need a few ten thousand events to identify the Earth effects, a few thousand
may be enough at scintillation detectors, which generically have a much better
energy resolution. A successful identification of the Earth effects through
this method can also provide $\Delta m^2_\odot$ to a good accuracy. The
relative strength of the detected Earth effects as a function of time provides
a test for supernova models.
