Volcanic seismicity of Villarrica Volcano

This thesis analyzes the nature and origin of the low-frequent seismicity of Villarrica
Volcano in Chile. Villarrica is an active volcano with an intermittent lava lake in its
central vent. The typical volcanic activity consists of persistent degassing and usually
mild Strombolian explosions and is accompanied by a notorious seismic tremor
overlain by swarms of transient events in approximately 1-min intervals. Both types of
signals display frequencies between 0.5 and 5 Hz. They are usually attributed to the
volcanic activity with the transients being interpreted as the bursting of slugs at the
surface of the lava lake (Strombolian explosions).

This work examines the origin of the tremor signal and the nature of the transient events.
The base for this work are 12 days of seismic data recorded by a dense local
seismic network in early March 2012. The results are most
likely applicable to today’s conditions since Villarrica is generally a stable system.

The tremor source was located in the crater area using three different
location methods. The occurrence of the transients in terms of magnitude and waiting time
between two events is statistically similar to properties found for gaseous slugs flowing
through a liquid-filled pipe and therefore supports the interpretation of these events as explosions.
The waveforms could be classified into at least 67 families although the majority belonged
to one of two families. The families likely originate in or close to the crater and share
a similar source region.


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