Fig. 4.From: Switching from seismic to seismo-acoustic harmonic tremor at a transition of eruptive activity during the Shinmoe-dake 2011 eruptionThree examples of seismo-acoustic harmonic tremor (SAHT) observed at SMN. In each case, the upper frames are the waveform and spectrogram of the vertical ground velocity and the lower frames are those of the acoustic signal. The first recognized SAHT event is shown in (a).Back to article page