The Augustine magmatic system as revealed by seismic tomography and relocated earthquake hypocenters from 1994 through 2009

Journal of Geophysical Research B: Solid Earth
By: , and 

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Abstract

We incorporate 14 years of earthquake data from the Alaska Volcano Observatory with data from a 1975 controlled-source seismic experiment to obtain the three-dimensional P and S wave velocity structure and the first high-precision earthquake locations at Augustine Volcano to be calculated in a fully three-dimensional velocity model. Velocity tomography shows two main features beneath Augustine: a narrow, high-velocity column beneath the summit, extending from ???2 km depth to the surface, and elevated velocities on the south flank. Our relocation results allow a thorough analysis of the spatio-temoral patterns of seismicity and the relationship to the magmatic and eruptive activity. Background seismicity is centered beneath the summit at an average depth of 0.6 km above sea level. In the weeks leading to the January 2006 eruption of Augustine, seismicity focused on a NW-SE line along the trend of an inflating dike. A series of drumbeat earthquakes occurred in the early weeks of the eruption, indicating further magma transport through the same dike system. During the six months following the onset of the eruption, the otherwise quiescent region 1 to 5 km below sea level centered beneath the summit became seismically active with two groups of earthquakes, differentiated by frequency content. The deep longer-period earthquakes occurred during the eruption and are interpreted as resulting from the movement of magma toward the summit, and the post-eruptive shorter-period earthquakes may be due to the relaxation of an emptied magma tube. The seismicity subsequently returned to its normal background rates and patterns. Copyright 2011 by the American Geophysical Union.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title The Augustine magmatic system as revealed by seismic tomography and relocated earthquake hypocenters from 1994 through 2009
Series title Journal of Geophysical Research B: Solid Earth
DOI 10.1029/2010JB008129
Volume 116
Issue 9
Year Published 2011
Language English
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Journal of Geophysical Research B: Solid Earth