LeBlanc, L.E., 2009, Icequakes and ice motion: A time-series analysis of the dynamics of the Bering Glacier, Alaska: University of Alaska Fairbanks, M.S. thesis, vii, 54 p., illust., maps.
We have acquired a year-long GPS record and a 16-month seismic data set from an array of co-located seismic and GPS stations established on Bering Glacier, Alaska, in spring 2007. A strong correlation exists between icequake occurrence and ice motion. The GPS motion record gives a mean annual horizontal velocity of 1.2 m d-1 and shows evidence of a spring speed-up, diurnal velocity fluctuations in summertime with peaks of up to 4 m d-1, a transient peak of 8 m d-1 associated with a major rainstorm, and winter quiescence. More than 1.5 million icequakes were detected, with rates of up to 600 events per hour. The seismic record shows an onset of high activity associated with spring speed up, followed by a shift into diurnal behavior by mid-summer. The seismic and motion records may reflect several reorganizations of the glacial hydraulic system that occurred in the late spring, in the fall, and in the late winter. Detected icequakes were organized into groups of similar waveforms to better investigate repeating events and associated source mechanisms. We propose several seismic source mechanisms to explain the time-series relationship between icequakes and ice motion including ice fracture, hydraulic transients, and basal recoupling.
Theses and Dissertations
