Seismic tremors and magma wagging during explosive volcanism

Low frequency volcanic tremor is a common feature of explosive volcanism and a key ingredient in assessments of volcanic hazard. Most models for volcanic tremor rely on specific properties of the geometry, structure and constitution of volcanic conduits, as well as the gas content of the erupting magma. Mark Jellinek and David Bercovici use a model of a silicic magma rising in a conduit as a columnar plug to demonstrate that, for most geologically relevant conditions, the magma column will oscillate or 'wag' against the restoring force of a highly vesicular annulus of sheared bubbles at observed tremor frequencies. They also find that the frequencies produced are relatively insensitive to the conduit structure and geometry.