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A tectonic earthquake sequence preceding the April-May 1999 eruption of Shishaldin Volcano, Alaska

Bulletin of Volcanology

By:
, , and
DOI: 10.1007/s00445-002-0226-1

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Abstract

On 4 March 1999, a shallow ML 5.2 earthquake occurred beneath Unimak Island in the Aleutian Arc. This earthquake was located 10-15 km west of Shishaldin Volcano, a large, frequently active basaltic-andesite stratovolcano. A Strombolian eruption began at Shishaldin roughly 1 month after the mainshock, culminating in a large explosive eruption on 19 April. We address the question of whether or not the eruption caused the mainshock by computing the Coulomb stress change caused by an inflating dike on fault planes oriented parallel to the mainshock focal mechanism. We found Coulomb stress increases of ???0.1 MPa in the region of the mainshock, suggesting that magma intrusion prior to the eruption could have caused the mainshock. Satellite and seismic data indicate that magma was moving upwards beneath Shishaldin well before the mainshock. indicating that, in an overall sense, the mainshock cannot be said to have caused the eruption. However, observations of changes at the volcano following the mainshock and several large aftershocks suggest that the earthquakes may, in turn, have influenced the course of the eruption.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
A tectonic earthquake sequence preceding the April-May 1999 eruption of Shishaldin Volcano, Alaska
Series title:
Bulletin of Volcanology
DOI:
10.1007/s00445-002-0226-1
Volume
64
Issue:
8
Year Published:
2002
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Bulletin of Volcanology
First page:
520
Last page:
524
Number of Pages:
5