The threshold for this method is about 5-10 GeV for vertical tracks, depending on the vertical distance between groups of optical modules, and about 15 GeV for more isotropic events, depending on the horizontal distance between lines. The muon range above 1 TeV increases only logarithmically with the muon energy. On the other hand, the detection efficiency increases with energy because of the additional energy loss. Monte Carlo studies have shown that the neutrino energy can be determined within a factor 3 above 1 TeV from the average energy loss. Above 1 PeV, the Earth becomes opaque to upward-going vertical neutrinos.
Higher energies are accessible closer to the horizon, however.
Very high-energy tau neutrinos can be observed because the produced in interactions decay before they are absorbed, producing of lower energy which continue along the original flight path, but with decreasing interaction probability, resulting in an accumulation of events at the highest detectable energies. Declinations below are always visible, while those above are never visible. Most of the Galactic plane is visible, and the Galactic centre is visible most of the sidereal day. At energies greater than TeV, the interaction length becomes smaller than the Earth's diameter for traversing the dense core of the Earth. Above 10 PeV, only nearly horizontal are visible.