Long-Period Seismicity At Shishaldin Volcano, Alaska

Dissertation (Ph.D.) University of Alaska Fairbanks, 2006 Since it last erupted in 1999, Shishaldin Volcano, Aleutian Islands, Alaska, has been characterized by a continuous and extremely high level of seismicity. The activity consists of many hundreds to thousands long-period (LP; 1-2 Hz) earthquak...

Full description

Bibliographic Details
Main Author: Petersen, Tanja
Other Authors: McNutt, Stephen R.
Format: Doctoral or Postdoctoral Thesis
Language:unknown
Published: 2006
Subjects:
Online Access:http://hdl.handle.net/11122/8915
id ftunivalaska:oai:scholarworks.alaska.edu:11122/8915
record_format openpolar
spelling ftunivalaska:oai:scholarworks.alaska.edu:11122/8915 2023-05-15T18:48:45+02:00 Long-Period Seismicity At Shishaldin Volcano, Alaska Petersen, Tanja McNutt, Stephen R. 2006 http://hdl.handle.net/11122/8915 unknown http://hdl.handle.net/11122/8915 Department of Geology and Geophysics Geophysics Dissertation phd 2006 ftunivalaska 2023-02-23T21:37:09Z Dissertation (Ph.D.) University of Alaska Fairbanks, 2006 Since it last erupted in 1999, Shishaldin Volcano, Aleutian Islands, Alaska, has been characterized by a continuous and extremely high level of seismicity. The activity consists of many hundreds to thousands long-period (LP; 1-2 Hz) earthquakes per day. The rate of one LP event every 0.5-5 minutes has remained more or less constant for the last 7 years. A high rate of LP seismicity has been associated with pre-eruptive activity at many other volcanoes presented in the volcano seismology literature. Shishaldin, however, shows no other signs of volcanic unrest except for a ~200 m high steam plume that nearly always emanates from the volcano's summit and occasional weak thermal anomalies observed in satellite imagery. This thesis investigates the nature of Shishaldin's unusual volcanic behavior, and provides a case-study that mainly focuses on seismic data recorded by the short-period monitoring network surrounding the volcano, but also integrates local infrasound data, visual observations and SO2 measurements. The observations suggest a steady-state volcanic process within an open conduit system that is capable of releasing a large amount of energy, approximately equivalent to at least one magnitude 1.8-2.6 earthquake per clay. Shishaldin infrasound signals recorded by a pressure sensor co-located with a seismic instrument are used to confine the source locations of the LP events to a depth of 240 +/- 200 m below the crater rim. The seismo-acoustic data suggest that the LP earthquakes are associated with degassing explosions, created by complex gas volume ruptures from a fluid-air interface. Measurements of the SO2 flux within the puffing summit plume have revealed low values (58 tons/day), suggestive of a hydrothermal system. Four time periods of increased earthquake amplitudes, which each lasted about 1-2 months; have been analyzed. The periods of elevated seismicity are characterized by an abundance of LP events with highly similar waveforms that ... Doctoral or Postdoctoral Thesis Alaska Aleutian Islands University of Alaska: ScholarWorks@UA Fairbanks
institution Open Polar
collection University of Alaska: ScholarWorks@UA
op_collection_id ftunivalaska
language unknown
topic Geophysics
spellingShingle Geophysics
Petersen, Tanja
Long-Period Seismicity At Shishaldin Volcano, Alaska
topic_facet Geophysics
description Dissertation (Ph.D.) University of Alaska Fairbanks, 2006 Since it last erupted in 1999, Shishaldin Volcano, Aleutian Islands, Alaska, has been characterized by a continuous and extremely high level of seismicity. The activity consists of many hundreds to thousands long-period (LP; 1-2 Hz) earthquakes per day. The rate of one LP event every 0.5-5 minutes has remained more or less constant for the last 7 years. A high rate of LP seismicity has been associated with pre-eruptive activity at many other volcanoes presented in the volcano seismology literature. Shishaldin, however, shows no other signs of volcanic unrest except for a ~200 m high steam plume that nearly always emanates from the volcano's summit and occasional weak thermal anomalies observed in satellite imagery. This thesis investigates the nature of Shishaldin's unusual volcanic behavior, and provides a case-study that mainly focuses on seismic data recorded by the short-period monitoring network surrounding the volcano, but also integrates local infrasound data, visual observations and SO2 measurements. The observations suggest a steady-state volcanic process within an open conduit system that is capable of releasing a large amount of energy, approximately equivalent to at least one magnitude 1.8-2.6 earthquake per clay. Shishaldin infrasound signals recorded by a pressure sensor co-located with a seismic instrument are used to confine the source locations of the LP events to a depth of 240 +/- 200 m below the crater rim. The seismo-acoustic data suggest that the LP earthquakes are associated with degassing explosions, created by complex gas volume ruptures from a fluid-air interface. Measurements of the SO2 flux within the puffing summit plume have revealed low values (58 tons/day), suggestive of a hydrothermal system. Four time periods of increased earthquake amplitudes, which each lasted about 1-2 months; have been analyzed. The periods of elevated seismicity are characterized by an abundance of LP events with highly similar waveforms that ...
author2 McNutt, Stephen R.
format Doctoral or Postdoctoral Thesis
author Petersen, Tanja
author_facet Petersen, Tanja
author_sort Petersen, Tanja
title Long-Period Seismicity At Shishaldin Volcano, Alaska
title_short Long-Period Seismicity At Shishaldin Volcano, Alaska
title_full Long-Period Seismicity At Shishaldin Volcano, Alaska
title_fullStr Long-Period Seismicity At Shishaldin Volcano, Alaska
title_full_unstemmed Long-Period Seismicity At Shishaldin Volcano, Alaska
title_sort long-period seismicity at shishaldin volcano, alaska
publishDate 2006
url http://hdl.handle.net/11122/8915
geographic Fairbanks
geographic_facet Fairbanks
genre Alaska
Aleutian Islands
genre_facet Alaska
Aleutian Islands
op_relation http://hdl.handle.net/11122/8915
Department of Geology and Geophysics
_version_ 1766242009933152256