The feasibility of generating low-frequency volcano seismicity by flow through a deformable channel.

Volcanic tremor: nonlinear excitation by fluid flow. Magma acoustics and time-varying melt properties at Arenal Volcano, Costa Rica. Physical models for the source of Lascar’s harmonic tremor. Cyclic eruptive behavior of silicic volcanoes. A new model for volcanic earthquake at Unzen Volcano: melt rupture model. Analysis of seismic and acoustic observations at Arenal Volcano, Costa Rica, 1995–1997. Seismicity of Ruapehu volcano, New Zealand, 1971–1996: a review. Sherburn, S., Bryan, C., Hurst, A., Latter, J. Source and path effects in the wave fields of tremor and explosions at Stromboli Volcano, Italy. Long-period volcano seismicity: its source and use in eruption forecasting. Ground surface deformation patterns, magma supply, and magma storage at Okmok volcano, Alaska, from InSAR analysis: 1. Lu, Z., Dzurisin, D., Biggs, J., Wicks, C. A comprehensive approach to monitoring volcano deformation as a window on the eruption cycle. Volcanic tremor during eruptions: temporal characteristics, scaling and constraints on conduit size and processes. Nature, wavefield properties and source mechanism of volcanic tremor: a review. Characteristics and causes of shallow seismicity in andesite volcanoes. Moreover, the model predicts that as an eruption proceeds there will be an upward drift in both the maximum frequency and the total signal frequency bandwidth, the nature of which depends on the explosivity of the eruption, as is often observed. In contrast to previous models, the magma-wagging oscillation is relatively insensitive to the conduit structure and geometry, which explains the narrow band of tremor frequencies observed around the world. We demonstrate that, for most geologically relevant conditions, the magma column will oscillate or ‘wag’ against the restoring ‘gas-spring’ force of the annulus at observed tremor frequencies. Here we employ the contemporary view that silicic magma rises in the conduit as a columnar plug surrounded by a highly vesicular annulus of sheared bubbles 9, 10. Indeed, this universality of tremor properties remains a major enigma. Because neither the initial structure nor the evolution of the magma-conduit system will be the same from one volcano to the next, it is surprising that tremor characteristics are so consistent among different volcanoes. 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. Volcanic tremor is thus of particular value for eruption forecasting 6, 8. Before major eruptions, tremor can occur in concert with increased gas flux and related ground deformation 5, 6, 7. This oscillation persists for minutes to weeks and is characterized by a remarkably narrow band of frequencies from about 0.5 Hz to 7 Hz (refs 1–4).

Volcanic tremor is a ubiquitous feature of explosive eruptions.

Wag seismac