The Complex Relationship between Seismic Velocity and Volcanic, Tectonic, and Environmental Forcings Illustrated by 23 Years of Data at Mt. St. Helens

Makus, Peter; Denolle, Marine; Sens‐Schönfelder, Christoph; Köpfli, Manuela; Tilmann, Frederik

doi:10.5194/egusphere-egu23-6757

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“…The origin times of the seismic events plotted in Sections 4 and 5 can be queried via the USGS FDSN web service. The seismic data download and the computation of correlations and dv/v were executed using SeisMIC 0.1.28 (Makus & Sens-Schönfelder, 2022, doi: https://doi.org/10.5880/GFZ.2.4.2022.002), available under the EUPL license agreement at https://github.com/PeterMakus/SeisMIC. TheSequencer algorithm (Baron & Ménard, 2021) that we used to sort the similarity matrices of the stations can be executed online at http:// sequencer.org, its source code can be downloaded at https://github.com/dalya/Sequencer.…”

Section: Data Availability Statementmentioning

confidence: 99%

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Deciphering the Whisper of Volcanoes: Monitoring Velocity Changes at Kamchatka's Klyuchevskoy Group With Fluctuating Noise Fields

et al. 2023

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Volcanic inflation and deflation often precede eruptions and can lead to seismic velocity changes (dv/v $dv/v$) in the subsurface. Recently, interferometry on the coda of ambient noise‐cross‐correlation functions yielded encouraging results in detecting these changes at active volcanoes. Here, we analyze seismic data recorded at the Klyuchevskoy Volcanic Group in Kamchatka, Russia, between summer of 2015 and summer of 2016 to study signals related to volcanic activity. However, ubiquitous volcanic tremors introduce distortions in the noise wavefield that cause artifacts in the dv/v $dv/v$ estimates masking the impact of physical mechanisms. To avoid such instabilities, we propose a new technique called time‐segmented passive image interferometry. In this technique, we employ a hierarchical clustering algorithm to find periods in which the wavefield can be considered stationary. For these periods, we perform separate noise interferometry studies. To further increase the temporal resolution of our results, we use an AI‐driven approach to find stations with similar dv/v $dv/v$ responses and apply a spatial stack. The impacts of snow load and precipitation dominate the resulting dv/v $dv/v$ time series, as we demonstrate with the help of a simple model. In February 2016, we observe an abrupt velocity drop due to the M7.2 Zhupanov earthquake. Shortly after, we register a gradual velocity increase of about 0.3% at Bezymianny Volcano coinciding with surface deformation observed using remote sensing techniques. We suggest that the inflation of a shallow reservoir related to the beginning of Bezymianny's 2016/2017 eruptive cycle could have caused this local velocity increase and a decorrelation of the correlation function coda.

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Section: Data Availability Statementmentioning

confidence: 99%

“…To execute these steps, we employ SeisMIC (Makus & Sens-Schönfelder, 2022), a freely available open-source software suite written in Python. SeisMIC is available on GitHub and will be discussed in detail in a separate publication.…”

Section: Seismic Datamentioning

confidence: 99%