Monochromatic Infrasonic Tremor Driven by Persistent Degassing and Convection at Villarrica Volcano, Chile

Infrasonic data collected at Villarrica volcano (Chile) in March 2009 show a sustained, continuous, infrasonic oscillation (tremor) with a monochromatic low frequency content at ∼0.75 Hz. This tremor is extremely stable in time both at the summit and at a distal (∼4 km) small aperture array. Infrasonic tremor is characterized by discrete high amplitude bursts with a cyclic recurrence time of ∼40 s and is well correlated (0.93) with seismic tremor. These new data are compared with previous datasets collected in 2002 and 2004 during different levels of activity. All data show the same persistent infrasonic tremor and have the same strong correlation with seismic tremor. The stability and correlation of infrasonic and seismic tremor indicate the existence of a sustained and continuous process, which we suggest is related to the gravity-driven bubble column dynamics responsible for conduit convection.