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Frictional-faulting model for harmonic tremor before Redoubt Volcano eruptions

August 1, 2013

Seismic unrest, indicative of subsurface magma transport and pressure changes within fluid-filled cracks and conduits, often precedes volcanic eruptions. An intriguing form of volcano seismicity is harmonic tremor, that is, sustained vibrations in the range of 0.5–5 Hz. Many source processes can generate harmonic tremor. Harmonic tremor in the 2009 eruption of Redoubt Volcano, Alaska, has been linked to repeating earthquakes of magnitudes around 0.5–1.5 that occur a few kilometres beneath the vent. Before many explosions in that eruption, these small earthquakes occurred in such rapid succession—up to 30 events per second—that distinct seismic wave arrivals blurred into continuous, high-frequency tremor. Tremor abruptly ceased about 30 s before the explosions. Here we introduce a frictional-faulting model to evaluate the credibility and implications of this tremor mechanism. We find that the fault stressing rates rise to values ten orders of magnitude higher than in typical tectonic settings. At that point, inertial effects stabilize fault sliding and the earthquakes cease. Our model of the Redoubt Volcano observations implies that the onset of volcanic explosions is preceded by active deformation and extreme stressing within a localized region of the volcano conduit, at a depth of several kilometres.

Publication Year 2013
Title Frictional-faulting model for harmonic tremor before Redoubt Volcano eruptions
DOI 10.1038/ngeo1879
Authors Ksenia Dmitrieva, Alicia J. Hotovec-Ellis, Stephanie G. Prejean, Eric M. Dunham
Publication Type Article
Publication Subtype Journal Article
Series Title Nature Geoscience
Index ID 70107482
Record Source USGS Publications Warehouse
USGS Organization Alaska Volcano Observatory