Fig. 4From: Anatomy of phreatic eruptionsVLPs and long-lasting oscillations at Kawah Ijen. a Vertical displacement and b spectra corresponding to the red window in (a). c Zoom on the first very-long-period (VLP) event and d spectra of the red window in (c). Instrument responses are deconvolved after detrending and high-pass filtering the data above 0.001Â Hz. The dominant period of VLP signals is 8 s with superimposed low-amplitude shorter oscillations [down to 1 s period, subplot (d)]. These long-lasting oscillations have distinct dominant periods at 17Â s, 27Â s and 50Â s [subplot (b)]Back to article page