Volcano dome dynamics at Mount St. Helens:Deformation and intermittent subsidence monitored by seismicity and camera imagery pixel offsets

Salzer, Jacqueline T. and Thelen, Weston A. and James, Michael Richard and Walter, Thomas R. and Moran, Seth and Denlinger, Roger (2016) Volcano dome dynamics at Mount St. Helens:Deformation and intermittent subsidence monitored by seismicity and camera imagery pixel offsets. Journal of Geophysical Research: Solid Earth, 121 (11). pp. 7882-7902. ISSN 2169-9356

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Abstract

The surface deformation field measured at volcanic domes provides insights into the effects of magmatic processes, gravity-and gas-driven processes, and the development and distribution of internal dome structures. Here we study short-term dome deformation associated with earthquakes at Mount St. Helens, recorded by a permanent optical camera and seismic monitoring network. We use Digital Image Correlation (DIC) to compute the displacement field between successive images and compare the results to the occurrence and characteristics of seismic events during a 6 week period of dome growth in 2006. The results reveal that dome growth at Mount St. Helens was repeatedly interrupted by short-term meter-scale downward displacements at the dome surface, which were associated in time with low-frequency, large-magnitude seismic events followed by a tremor-like signal. The tremor was only recorded by the seismic stations closest to the dome. We find a correlation between the magnitudes of the camera-derived displacements and the spectral amplitudes of the associated tremor. We use the DIC results from two cameras and a high-resolution topographic model to derive full 3-D displacement maps, which reveals internal dome structures and the effect of the seismic activity on daily surface velocities. We postulate that the tremor is recording the gravity-driven response of the upper dome due to mechanical collapse or depressurization and fault-controlled slumping. Our results highlight the different scales and structural expressions during growth and disintegration of lava domes and the relationships between seismic and deformation signals.

Item Type:
Journal Article
Journal or Publication Title:
Journal of Geophysical Research: Solid Earth
Additional Information:
An edited version of this paper was published by AGU. Copyright 2016) American Geophysical Union.
Subjects:
ID Code:
86625
Deposited By:
Deposited On:
07 Jun 2017 13:06
Refereed?:
Yes
Published?:
Published
Last Modified:
07 Jul 2020 05:21