Sensitivity to lunar cycles prior to the 2007 eruption of Ruapehu volcano

A long-standing question in Earth Science is the extent to which seismic and volcanic activity can be regulated by tidal stresses, a repeatable and predictable external excitation induced by the Moon-Sun gravitational force. Fortnightly tides, a similar to 14-day amplitude modulation of the daily tidal stresses that is associated to lunar cycles, have been suggested to affect volcano dynamics. However, previous studies found contradictory results and remain mostly inconclusive. Here we study how fortnightly tides have affected Ruapehu volcano (New Zealand) from 2004 to 2016 by analysing the rolling correlation between lunar cycles and seismic amplitude recorded close to the crater. The long-term (similar to 1-year) correlation is found to increase significantly (up to confidence level of 5-sigma) during the similar to 3 months preceding the 2007 phreatic eruption of Ruapehu, thus revealing that the volcano is sensitive to fortnightly tides when it is prone to explode. We show through a mechanistic model that the real-time monitoring of seismic sensitivity to lunar cycles may help to detect the clogging of active volcanic vents, and thus to better forecast phreatic volcanic eruptions

geochemistry and geophysics of active volcanic lakes an introduction

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Turbulence-induced bubble nucleation in hydrothermal fluids beneath Yellowstone Lake

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Caudron, C., Vandemeulebrouck, J., & Sohn, R. A. Turbulence-induced bubble nucleation in hydrothermal fluids beneath Yellowstone Lake. Communications Earth & Environment, 3(1), (2022): 103, https://doi.org/10.1038/s43247-022-00417-6.Volcanic systems generate large amounts of gas, and understanding gas fluxes is a fundamental aspect of volcanology and hazard mitigation. Volcanic gases can be challenging to measure, but acoustic methods hold promise in underwater environments because gas bubbles are powerful sound sources. We deployed an acoustic system to study the nature of gas discharge at a large (~30 MW) thermal field on the floor of Yellowstone Lake, which has experienced numerous hydrothermal explosions since the last glaciation (~13.4 ka). We find that small (<10 Pa) turbulent flow instabilities trigger the nucleation of CO2 bubbles in the saturated fluids. The observation of CO2 bubbles nucleating in hydrothermal fluids due to small pressure perturbations informs our understanding of hydrothermal explosions in Yellowstone Lake, and demonstrates that acoustic data in underwater environments can provide insight into the stability of gas-rich systems, as well as gas fluxes.This research was supported by the National Science Foundation grant EAR-1516361 to R.A.S. All work in Yellowstone National Park was completed under an authorized research permit (YELL-2018-SCI-7018). We also acknowledge the IRGA 2021 Volquan project (funded by Université Grenoble Alpes) and Thomas Jefferson Fund Face Foundation (project TJF20_009 ‘Quantifying underwater volcano degassing using novel seismo-acoustic approaches’)

Relative seismic velocity variations correlate with deformation at Kīlauea volcano, Hawai'i

Seismic noise interferometry allows the continuous and real-time measurement of relative seismic velocity through a volcanic edifice. Because seismic velocity is sensitive to the pressurization state of the system, this method is an exciting new monitoring tool at active volcanoes. Despite the potential of this tool, no studies have yet comprehensively compared velocity to other geophysical observables on a short-term time scale at a volcano over a significant length of time. We use volcanic tremor (~0.3 to 1.0 Hz) at Kīlauea as a passive source for interferometry to measure relative velocity changes with time. By cross-correlating the vertical component of day-long seismic records between ~230 station pairs, we extract coherent and temporally consistent coda wave signals with time lags of up to 120 s. Our resulting time series of relative velocity shows a remarkable correlation between relative velocity and the radial tilt record measured at Kīlauea summit, consistently correlating on a time scale of days to weeks for almost the entire study period (June 2011 to November 2015). As the summit continually deforms in deflation-inflation events, the velocity decreases and increases, respectively. Modeling of strain at Kīlauea suggests that, during inflation of the shallow magma reservoir (1 to 2 km below the surface), most of the edifice is dominated by compression—hence closing cracks and producing faster velocities—and vice versa. The excellent correlation between relative velocity and deformation in this study provides an opportunity to understand better the mechanisms causing seismic velocity changes at volcanoes, and therefore realize the potential of passive interferometry as a monitoring tool

The gravity of geophysics

A recent article in Reviews of Geophysics examined terrestrial techniques for measuring changes in gravity over time and their application to the geosciences.</jats:p

Temporal Seismic Velocity Changes During the 2020 Rapid Inflation at Mt. Þorbjörn-Svartsengi, Iceland, Using Seismic Ambient Noise

Publisher Copyright: © 2021. The Authors.Repeated periods of inflation-deflation in the vicinity of Mt. Þorbjörn-Svartsengi, SW-Iceland, were detected in January–July, 2020. We used seismic ambient noise and interferometry to characterize temporal variations of seismic velocities (dv/v, %). This is the first time in Iceland that dv/v variations are monitored in near real-time during volcanic unrest. The seismic station closest to the inflation source center (∼1 km) showed the largest velocity drop (∼1%). Different frequency range measurements, from 0.1 to 2 Hz, show dv/v variations, which we interpret in terms of varying depth sensitivity. The dv/v correlates with deformation measurements (GPS, InSAR), over the unrest period, indicating sensitivity to similar crustal processes. We interpret the velocity drop to be caused by crack opening triggered by intrusive magmatic activity. We conclude that single-station cross-component analyses provide the most robust solutions for early detection of magmatic activity.Peer reviewe

Temporal Changes of Seismic Velocity Caused by Volcanic Activity at Mt. Etna Revealed by the Autocorrelation of Ambient Seismic Noise

On active volcanoes, ambient noise-based seismic interferometry, able to detect very slight variations in seismic velocity associated with magma transport towards the surface, can be a very useful monitoring tool. In this work, we performed the autocorrelation of ambient seismic noise recorded at Mt. Etna volcano, by three stations located close to the active summit craters, during April 2013 - October 2014. Such an interval was chosen because of the number and variety of eruptions. The method implemented to perform autocorrelation was the phase cross-correlation, which does not require normalization of the signals. The detected seismic velocity variations were very consistent for all three stations throughout the study period, mainly ranging between 0.3 and -0.2%, and were time-related to both sequences of paroxysmal eruptions and more effusive activities. In particular, we observed seismic velocity decreases accompanying paroxysmal eruptions, suggesting an intense pressurization within the plumbing system, which created an area of extensional strain with crack openings. It is worth noting that classical cross-station approach failed to detect seismic velocity changes related to volcano activity. In addition, seismic velocity variations over time were integrated with ground deformation data recorded by GPS stations and volcanic tremor centroid locations. Finally, we showed that, although the investigated frequency band (1-2 Hz) contains most of the volcanic tremor energy, our results did not indicate a particular contamination of seismic velocity variation measurements by variations of tremor sources

Seismic Amplitude Ratio Analysis of the 2014-2015 Bárðarbunga-Holuhraun Dike Propagation and Eruption

Magma is transported in brittle rock through dikes and sills. This movement may be accompanied by the release of seismic energy that can be tracked from the Earth's surface. Locating dikes and deciphering their dynamics is therefore of prime importance in understanding and potentially forecasting volcanic eruptions. The Seismic Amplitude Ratio Analysis (SARA) method aims to track melt propagation using the amplitudes recorded across a seismic network without picking the arrival times of individual earthquake phases. This study validates this methodology by comparing SARA locations (filtered between 2 and 16 Hz) with the earthquake locations (same frequency band) recorded during the 2014–2015 Bár urn:x-wiley:jgrb:media:jgrb52508:jgrb52508-math-0003arbunga‐Holuhraun dike intrusion and eruption in Iceland. Integrating both approaches also provides the opportunity to investigate the spatiotemporal characteristics of magma migration during the dike intrusion and ensuing eruption. During the intrusion SARA locations correspond remarkably well to the locations of earthquakes. Several exceptions are, however, observed. (1) A low‐frequency signal was possibly associated with a subglacial eruption on 23 August. (2) A systematic retreat of the seismicity was also observed to the back of each active segment during stalled phases and was associated with a larger spatial extent of the seismic energy source. This behavior may be controlled by the dike's shape and/or by dike inflation. (3) During the eruption SARA locations consistently focused at the eruptive site. (4) Tremor‐rich signal close to ice cauldrons occurred on 3 September. This study demonstrates the power of the SARA methodology, provided robust site amplification; Quality Factors and seismic velocities are available.The authors thank both reviewers, the Associate Editor, and the Editor for their insightful comments and suggestions that greatly improved this study. Seismometers were borrowed from the Natural Environment Research Council (NERC) SEIS-UK facility (loans 968 and 1022), with funding by research grants from the NERC and the European Community’s Seventh Framework Programme grant 308377 (Project FUTUREVOLC), and graduate studentships from the NERC. C. Caudron benefited from a Fondation Wiener Anspach postdoctoral fellowship, then from a FNRS Chargé de Recherche postdoctoral grantPeer Reviewe

Messages in the bubbles

Laacher See volcano is quiet, but gas bubbles rising through the overlying lake are a reminder of its potential hazard. Scientists took a close look at the bubbles to test eruption monitoring methods