Two Decades of Seismicity at Mount St. Helens
Description:
Detection and cataloging of seismicity from Mount St. Helens, the most active and well-instrumented volcano in the Cascade Range, is vital for imaging its active structures at depth. The Pacific Northwest Seismic Network (PNSN) earthquake catalog, assembled by analyst-picked earthquakes located with a one-dimensional regional velocity model, spans several decades and provides fundamental observations for many studies of the volcano’s activity. The recent implementation of data-driven machine learning algorithms in seismic monitoring workflows has enabled the development of extremely detailed seismicity catalogs with several times as many earthquakes as analyst-picked catalogs. Additionally, relocations of the PNSN catalog earthquakes with 3D travel time grids derived from improved velocity models show a shift in location by several kilometers, and can change interpretations of volcanic processes.
To improve the quality of the earthquake catalog at Mount. St. Helens, we train a convolutional neural network to identify P and S wave arrival time picks in continuous seismic data starting in the early 2000s using analyst-made arrival time picks in the PNSN catalog. We then associate the phase picks using GaMMA, a Gaussian Mixed Model clustering algorithm, and compute absolute locations of the associated phase pick clusters via gridsearch of travel time grids derived from 3D velocity models of the Mount St. Helens region. Lastly, we refine locations using a double-difference location procedure to improve precision. With the improved seismicity catalog, we are able to further reveal the conditions that govern magma transport from deep and shallow environments, the origins of volcano tectonic earthquakes, as well as the evolution of the 2004-2008 eruptive period.
Session: Seismology's Role in Assessing Volcanic Hazard at Multiple Time Scales [Poster]
Type: Poster
Date: 4/18/2023
Presentation Time: 08:00 AM (local time)
Presenting Author: Brenton W. Hirao
Student Presenter: Yes
Invited Presentation:
Authors
Brenton Hirao Presenting Author Corresponding Author bhirao@uoregon.edu University of Oregon |
Amanda Thomas amt.seismo@gmail.com University of Oregon |
Han Zhang hanzhang@unm.edu University of New Mexico |
Brandon Schmandt bschmandt@unm.edu University of New Mexico |
Weston Thelen wthelen@usgs.gov U.S. Geological Survey, Cascades Volcano Observatory |
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Two Decades of Seismicity at Mount St. Helens
Category
Seismology's Role in Assessing Volcanic Hazard at Multiple Time Scales