Relating deep magmatic processes to eruptive behavior at arc volcanoes through an analysis of deep seismicity

Thesis (M.S.) University of Alaska Fairbanks, 2010"In this thesis, the seismicity at depths greater than 15 km beneath two sets of volcanic centers, the Klyuchevskoy Volcanic Group (KVG), Russia and Mount Spurr, Alaska is examined. In both regions, a pulsing pattern of deep seismicity is observed with many cycles following eruptive activity or periods of unrest. The bulk of the seismicity beneath the KVG is comprised of long-period events many of which share a similar appearance. Cross correlation of the waveforms for events occurring between 12/24/2007 and 12/31/2008 show a number of event families occurring over long time spans. New relative locations for these families which better constrain their spatial extent are derived. The pulsing pattern of seismicity seen here is in close keeping with the expected cyclic nature of melt segregation which occurs as melt leaves the site of generation and ascends to shallower levels. Based on evidence in the data, a model is proposed whereby melt segregation on the time scales necessary to facilitate eruptions is attributable to a pressure response in the deep system induced by the removal of material in the shallow chamber during an eruptive cycle"--Leaf iii.1. Characterization of deep seismicity beneath the KVG, Kamchatka -- 1.1. Regional setting -- 1.2. The data -- 1.3. Anatomy of deep low frequency earthquakes -- 1.3.1. Waveform characteristics -- 1.3.2. Comparing deep long-period events to other seismicity at these volcanoes -- 1.3.3. Event magnitudes -- 1.4. Patterns of deep seismicity -- 1.5. Assessing the validity of temporal seismicity pattern -- 2. Exploring through the seismicity cloud to highlight fine scale structures beneath the Klyuchevskoy Volcano group -- 2.1. Introduction -- 2.2. Long lived source processes -- 2.3. Improved event locations -- 2.4. Initial event relocation using the hypodd analysis -- 2.5.1. The ultimate hypoDD run -- 3. Analysis of Mount Spurr data -- 3.1. Introduction -- 3.2. The data -- 3.3. Characterization of deep seismicity beneath Mount Spurr -- 3.3.1. Event types in the Mount Spurr dataset -- 3.3.2. Event amplitudes and magnitudes -- 3.4. Focal mechanisms -- 3.5. The search for multiplets within the Spurr data set -- 3.6. Reevaluating locations at Mount Spurr for events occurring during the summer of 2005 -- Conclusion -- References