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Volcano dome dynamics at Mount St. Helens: Deformation and intermittent subsidence monitored by seismicity and camera imagery pixel offsets
Author(s) -
Salzer Jacqueline T.,
Thelen Weston A.,
James Mike R.,
Walter Thomas R.,
Moran Seth,
Denlinger Roger
Publication year - 2016
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2016jb013045
Subject(s) - geology , dome (geology) , seismology , lava dome , volcano , induced seismicity , displacement (psychology) , fault (geology) , deformation (meteorology) , geodesy , lava , geomorphology , psychology , oceanography , psychotherapist
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.