Volcanic tremor induced by gas-liquid two-phase flow: Implications of density wave oscillation

[1] We model the source mechanism of volcanic tremor at shallow depths of a volcano by hydrothermal dynamics. Steam-water two-phase flow in the pipe is formulated, and its instability, known as density wave oscillation, can produce monotonic characteristics similar to those of a volcanic tremor. The oscillation is closely related to the heat supplied to the system and we quantitatively obtain the upper and lower limits of the heating quantity to realize this monotonic oscillation. This source mechanism can be realized only when the effect of gravity is small (i.e., horizontal flow), since the effect of depressurization due to upwelling is significant for bubble growth with vertical flow including gravity, and heating and vaporization are less important.