Shallow repeating seismic events under an alpine glacier at Mount Rainier, Washington, USA

Journal of Glaciology
By: , and 

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Abstract

We observed several swarms of repeating low-frequency (1–5 Hz) seismic events during a 3 week period in May–June 2010, near the summit of Mount Rainier, Washington, USA, that likely were a result of stick–slip motion at the base of alpine glaciers. The dominant set of repeating events ('multiplets') featured >4000 individual events and did not exhibit daytime variations in recurrence interval or amplitude. Volcanoes and glaciers around the world are known to produce seismic signals with great variability in both frequency content and size. The low-frequency character and periodic recurrence of the Mount Rainier multiplets mimic long-period seismicity often seen at volcanoes, particularly during periods of unrest. However, their near-surface location, lack of common spectral peaks across the recording network, rapid attenuation of amplitudes with distance, and temporal correlation with weather systems all indicate that ice-related source mechanisms are the most likely explanation. We interpret the low-frequency character of these multiplets to be the result of trapping of seismic energy under glacial ice as it propagates through the highly heterogeneous and attenuating volcanic material. The Mount Rainier multiplet sequences underscore the difficulties in differentiating low-frequency signals due to glacial processes from those caused by volcanic processes on glacier-clad volcanoes.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Shallow repeating seismic events under an alpine glacier at Mount Rainier, Washington, USA
Series title Journal of Glaciology
DOI 10.3189/2013JoG12J111
Volume 59
Issue 214
Year Published 2013
Language English
Publisher International Glaciological Society
Publisher location Cambridge, UK
Contributing office(s) Volcano Science Center
First page 345
Last page 356
Country United States
State Washington
Other Geospatial Mount Rainier
Online Only (Y/N) N
Additional Online Files (Y/N) N