  Based on our recent three-dimensional core-collapse supernova (CCSN)
simulations including both exploding and non-exploding models, we study the
detailed neutrino signals in representative terrestrial neutrino observatories,
Super-Kamiokande (Hyper-Kamiokande), DUNE, JUNO, and IceCube. We find that the
physical origin of difference in the neutrino signals between 1D and 3D is
mainly proto-neutron-star (PNS) convection. We study the temporal and angular
variations of the neutrino signals and discuss the detectability of the time
variations driven by the spiral Standing Accretion Shock Instability (spiral
SASI) when it emerges for non-exploding models. In addition, we determine that
there can be a large angular asymmetry in the event rate ($\gtrsim 50 \%$), but
that the time-integrated signal has a relatively modest asymmetry ($\lesssim 20
\%$). Both features are associated with the lepton-number emission
self-sustained asymmetry (LESA) and the spiral SASI. Moreover, our analysis
suggests that there is an interesting correlation between the total neutrino
energy (TONE) and the cumulative number of neutrino events in each detector, a
correlation that can facilitate data analyses of real observations. We
demonstrate the retrieval of neutrino energy spectra for all flavors of
neutrino by applying a novel spectrum reconstruction technique to the data from
multiple detectors. We find that this new method is capable of estimating the
TONE within the error of $\sim$20\% if the distance to the CCSN is $\lesssim 6$
kpc.
