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74. Evaluating the Influence of Atmospheric Conditions on Infrasound Data Recorded at Volcán Villarrica (Chile)

Scott J. Gauvain, Dr. Jeffrey B. Johnson, Dr. Jacob Anderson, Jerry C. Mock

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The continuous and powerful infrasound from Villarrica may be used to invert for atmospheric conditions, which will influence signal arrival times. The figure below shows a volcanic signal recorded by 4 neighboring stations. Further work will reveal the effective sound speed lapse rates, in units of meters per second per kilometer, as radial distance from the acoustic source increases.

Volcanic signal recorded by 4 neighboring stations
Recordings from Station R075, Station R051, Station R102, and Station R055 in Pressure (pascals) over Time (miliseconds)

The signal above contains a frequency range between 1 and 5 Hz. It was filtered within this range in order to eliminate any noise not produced by the volcano itself. Commonly, active, open vent volcanoes produce a frequency between 1 and 2 Hz. Villarrica’s characteristic frequency at the time of data collection was around 1.1 Hz.


Infrasound is acoustic energy with low frequencies often below the threshold of human hearing (<20 Hz). Continuous infrasound is produced by Chile’s Volcán Villarrica and may be recorded with specialized microphones. In January, 2020 our team deployed 18 infrasound sensors oriented in a linear fashion from the volcanic crater out to 10 km at roughly 400 meter intervals. The objective was to evaluate how atmospheric conditions change expected infrasonic signal. Station locations are plotted below.

map of station locations


It is advantageous to pick station locations away from potential sources of noise such as wind or humans.

Stations will be grouped by distance from Villarrica’s crater. The sound arrival times by group will be averaged and compared to a theoretical value.

Sensors: GEM V1.01

GEM V1.01 infrasound sensors, developed by Boise State University’s Dr. Jacob F. Anderson, are ideal for deployments requiring many array elements. These sensors are small, lightweight, virtually weather-proof, and are manufactured here at Boise State University by every contributing author.

27 sensors packaged and stacked on a table
Image source: Jerry C. Mock


The sound speed lapse rates and atmospheric factors which cause them will be determined in future work. Further research will include using a sound propagation model to compare with observations.