Fig. 4From: Analyzing the continuous volcanic tremors detected during the 2015 phreatic eruption of the Hakone volcanoExamples of the velocity waveforms (vertical component) and spectrograms at OWD station. a Volcanic tremor at 03:30:00 on July 1 and b VT earthquakes at 06:36:20 on June 30. Each spectrogram was calculated by using a 2.56 s time window with 0.2 s intervalsBack to article page