Volcanic tremor on Kilauea, Hawai';i - Is something new in the plumbing system?

Volcanic tremor is a ubiquitous feature of active volcanism. However, the use of volcanic tremor as an accurate forecasting tool is still not possible because the underlying physical processes and their variation from one volcanic setting to the next remain opaque. In order to identify key dynamics of tremor and their relationship to magmatic and tectonic processes, we investigate links between the temporal evolution of tremor properties (e.g. frequency) and other indicators of volcanic unrest (e.g. changes in lava lake height, tilt). A practical hurdle is that appropriately correlated geophysical time series must be available. We examine seismic data from 11 stations during the 2011 Kamoamoa eruption (06-10 March), Kilauea, Hawai';i. Volcanic tremor persisted throughout the eruptive episode with varying amplitudes. The spectra show a broadband signal without clear harmonics. Most of its energy is concentrated below 15 Hz, with a peak between 1 and 2 Hz. For the first time on Kilauea, we detect a systematic temporal variation in the frequency of a spectral peak (frequency gliding). During the gliding episodes, there is a linear shift of energy up from 0.5-5.5 Hz and back down over several hours. We search for gliding during previous episodes of activity at Kilauea in 2007-2008, and compare different tremor episodes to identify potential changes in the plumbing system. Furthermore, we investigate how the characteristics of tremor at Kilauea compare to other ocean island settings and continental and oceanic arc volcanoes. Our approach can provide critical clues for the tremor source mechanism at Kilauea.