Modelling the macroscopic behavior of Strombolian explosions at Erebus volcano

We analyze seismic signals associated with the Strombolian explosion-quakes at Erebus volcano (Antarctica), examining the high-frequency ( > 0.5 Hz) portion of the spectrum. We consider recordings relative to two time periods during the years 2005 and 2006. Cross-correlation analysis allows us to distinguish three classes of events. Spectral properties and polarization analysis provide evidence of a very complex volcanic structure. We conduct analyses to elucidate the macroscopic dynamic system associated with the explosions. The distribution of the times between successive explosion-quakes is exponential, implying a Poissonian process as observed at Stromboli volcano but on a different time scale. The sequence of the occurrence of the explosions can be described by classical intermittency. A coalescence Chandrasekar–Landau mean-field model reproduces gas bubble sizes comparable with those observed at the lava lake surface. Finally, the classical equation for the ascent of gas bubbles is generalized by adding a diffusive process. This model provides ascent velocities depending on the bubble radius: for gas bubbles greater than a few centimeters, variation in ascent velocity due to diffusion becomes negligible and the ascent velocity appears to be governed primarily by buoyancy.