Experimental Modeling of Infrasound Emission from Slug Bursting on Volcanoes

The acoustic signal produced by gas slugs bursting at volcano vents is investigated by means of laboratory experiments. In order to explore the transition between linear and nonlinear acoustics, we model the bubble by an overpressurized cylindrical cavity closed by a membrane. We find that the acoustic waveform inside and outside the cavity, produced by the membrane bursting, is well described by the linear acoustics equations and a monopole source model up to an initial overpressure inside the cavity of about 24 kPa. For higher overpressure, the amplitude inside the conduit is smaller than the linear prediction, whereas the amplitude measured outside is larger. The frequency content remains harmonic, even at high initial overpressure. Changing the bursting depth in the conduit does not change the scaling of the amplitudes but affects the waveform and energy partitioning. We show that the energy of the first signal period is about 30% of the total acoustic energy and can be used as a good estimate, with a geometrical correction to account for the bursting depth. Key Points No simple relationship between the acoustic amplitude and bubble overpressureBelow ?P = 24 kPa, the monopole source theory holds trueThe energy computed over the first period is a good proxy for the total energy ©2014. American Geophysical Union. All Rights Reserved.