Anisotropy, repeating earthquakes, and seismicity associated with the 2008 eruption of Okmok Volcano, Alaska
Journal of Geophysical Research
By: Jessica H. Johnson, Stephanie Prejean, Martha K. Savage, and John Townend
Links
- More information: Publisher Index Page (via DOI)
- Open Access Version: Publisher Index Page
- Download citation as: RIS | Dublin Core
Abstract
We use shear wave splitting (SWS) analysis and double-difference relocation to examine temporal variations in seismic properties prior to and accompanying magmatic activity associated with the 2008 eruption of Okmok volcano, Alaska. Using bispectrum cross-correlation, a multiplet of 25 earthquakes is identified spanning five years leading up to the eruption, each event having first motions compatible with a normal fault striking NE–SW. Cross-correlation differential times are used to relocate earthquakes occurring between January 2003 and February 2009. The bulk of the seismicity prior to the onset of the eruption on 12 July 2008 occurred southwest of the caldera beneath a geothermal field. Earthquakes associated with the onset of the eruption occurred beneath the northern portion of the caldera and started as deep as 13 km. Subsequent earthquakes occurred predominantly at 3 km depth, coinciding with the depth at which the magma body has been modeled using geodetic data. Automated SWS analysis of the Okmok catalog reveals radial polarization outside the caldera and a northwest-southeast polarization within. We interpret these polarizations in terms of a magma reservoir near the center of the caldera, which we model with a Mogi point source. SWS analysis using the same input processing parameters for each event in the multiplet reveals no temporal changes in anisotropy over the duration of the multiplet, suggesting either a short-term or small increase in stress just before the eruption that was not detected by GPS, or eruption triggering by a mechanism other than a change of stress in the system.
Suggested Citation
Johnson, J.H., Prejean, S., Savage, M.K., and Townend, J., 2010, Anisotropy, repeating earthquakes, and seismicity associated with the 2008 eruption of Okmok Volcano, Alaska: Journal of Geophysical Research, v. 115, B00B04; 21 p., https://doi.org/10.1029/2009JB006991.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Anisotropy, repeating earthquakes, and seismicity associated with the 2008 eruption of Okmok Volcano, Alaska |
| Series title | Journal of Geophysical Research |
| DOI | 10.1029/2009JB006991 |
| Volume | 115 |
| Publication Date | September 11, 2010 |
| Year Published | 2010 |
| Language | English |
| Publisher | American Geophysical Union |
| Publisher location | Washington, D.C. |
| Contributing office(s) | Volcano Science Center |
| Description | B00B04; 21 p. |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Journal of Geophysical Research |
| Country | United States |
| State | Alaska |
| Other Geospatial | Okmok Volcano |