Fig. 2From: Preparatory and precursory processes leading up to the 2014 phreatic eruption of Mount Ontake, JapanVelocity seismograms and associated spectrograms of a VT earthquake (a) and an LP event (b) recorded at the V.ONTN station (NS component). Each spectrogram is calculated from the spectral amplitudes of velocity versus frequency in a moving 1-s window running through the entire seismogram (98 % overlap), as shown above each spectrogramBack to article page