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

2019 ◽  
Vol 6 ◽  
Author(s):  
Raphael S. M. De Plaen ◽  
Andrea Cannata ◽  
Flavio Cannavo' ◽  
Corentin Caudron ◽  
Thomas Lecocq ◽  
...  
Keyword(s):  
Volcanic Activity ◽  
Seismic Noise ◽  
Seismic Velocity ◽  
Temporal Changes ◽  
Ambient Seismic Noise ◽  
Mt Etna

Ambient seismic noise monitoring: an online application for decision makers – example of various applications for different slopes configurations.

2020 ◽  
Author(s):  
Alexandra Royer ◽  
Mathieu Le Breton ◽  
Antoine Guillemot ◽  
Noélie Bontemps ◽  
Eric Larose ◽  
...  
Keyword(s):  
Seismic Noise ◽  
Seismic Velocity ◽  
Early Warning Systems ◽  
Soil Liquefaction ◽  
Decision Makers ◽  
Velocity Variation ◽  
Ambient Seismic Noise ◽  
Landslide Monitoring ◽  
Velocity Change ◽  
Online Application

<p>Monitoring landslides is essential to understand their dynamics and to reduce the risk of human losses by detecting precursors before failures. In general, surface observations need to be complemented by observation at depth, in the bulk of the material. A decade ago, the ambient seismic noise interferometry method was proposed to monitor changes in the seismic surface wave velocity. As seismic wave velocities are directly related to the rigidity of the material, any reduction of seismic velocity can be associated to a loss of rigidity with high probability (a route toward soil liquefaction or to high fracturation). This technique led to detect a velocity decrease several days before the failure of a clayey landslide [1], paving the way to a novel precursor signal that could serve for alert or early warning systems. Here we report at least five different landslides that have been monitored, over several years [2]. In this paper, we detail the standard experimental configuration, the basic signal processing procedure, the sensitivity and resolution of the method, together with its advantages and possible limitations. Environmental effects on the relative seismic velocity change are discussed.</p><p>In order to make the technology operational for decision makers, we built an online application with web portal displaying daily evolution of seismic velocity variation. This portal also integrates other available observations like environmental parameters (weather, precipitations) or surface observation (photogrammetry, gps, extensometers…).</p><p>[1] G. Mainsant, E. Larose, C. Brönnimann, D. Jongmans, C. Michoud, M. Jaboyedoff, <em>Ambient seismic noise monitoring of a clay landslide : toward failure prediction</em>, J. Geophys. Res. <strong>117</strong>, F01030 (2012).</p><p>[2] M. Le Breton, N. Bontemps, A. Guillemot, L. Baillet, E. Larose,<sup> </sup><em>Landslide Monitoring Using Seismic Ambient Noise In-terferometry: Challenges and Applications,</em> Earth Science Review (under review) (2020)</p>

Temporal seismic velocity changes during the 2020 rapid inflation at Mt. Thorbjorn-Svartsengi, Iceland, using ambient seismic noise

2021 ◽  
Author(s):  
Yesim Cubuk Sabuncu ◽  
Kristin Jonsdottir ◽  
Corentin Caudron ◽  
Thomas Lecocq ◽  
Michelle Maree Parks ◽  
...  
Keyword(s):  
Seismic Wave ◽  
Seismic Noise ◽  
Seismic Velocity ◽  
Ambient Seismic Noise ◽  
Magmatic Activity ◽  
Volcanic Unrest ◽  
Seismic Velocity Changes ◽  
Magmatic Intrusions ◽  
Reykjanes Peninsula ◽  
Velocity Changes

<p>The Reykjanes peninsula, SW Iceland, was struck by intense earthquake swarm activity that occurred in January-July 2020 due to repeated magmatic intrusions in the Reykjanes-Svartsengi volcanic system. GPS and InSAR observations confirmed surface deformation centered near Mt. Thorbjorn, and during the unrest period, approximately ~14,000 earthquakes (-2≤M≤4.9) were reported at the Icelandic Meteorological Office (IMO). We investigate the behavior of the crust as a response to these repeated intrusions to provide insights into volcanic unrest in the Reykjanes peninsula. Our study presents temporal seismic wave velocity variations (dv/v, in percent) based on ambient noise seismic interferometry using continuous three-component waveforms collected by IMO, (http://www.vedur.is) for the period from April 2018 to November 2020. The state-of-the-art MSNoise software package (http://www.msnoise.org) is used to calculate cross-correlations of ambient seismic noise and to quantify the relative seismic velocity variations. We observe that magmatic intrusions in the vicinity of Mt. Thorbjorn-Svartsengi have considerably reduced the seismic wave velocities (dv/v, -1%) in the 1-2 Hz frequency band. Seismic velocity changes were compared with local seismicity, GPS and InSAR data recorded close to the repeated intrusions, and modelled volumetric strain changes. We found a good correlation between the dv/v variations and the available deformation data. The Rayleigh wave phase-velocity sensitivity kernels showed that the changes occurring at depths down to ~3-4 km in the crust were captured by our measurements. We interpret the relative seismic velocity decrease to be caused by crack opening induced by intrusive magmatic activity. Monitoring the Mt. Thorbjorn-Svartsengi volcanic unrest is crucial for successful early warning of volcanic hazards since the center of uplift is only 2km away from a fishing village and major infrastructure in the area, such as water supply and geothermal power. For the first time in Iceland, we have provided near-real-time dv/v variations to obtain a more complete picture of this magmatic activity. Our findings are supported by the analysis of other primary monitoring streams. We propose that this technique may be useful for early detection of future intrusions/increased magmatic activity. This study is supported by the Icelandic Research Fund, Rannis (Grant No: 185209-051).</p>

scholarly journals Monitoring transient changes within overpressured regions of subduction zones using ambient seismic noise

2016 ◽  
Vol 2 (1) ◽  
pp. e1501289 ◽  
Author(s):  
Esteban J. Chaves ◽  
Susan Y. Schwartz
Keyword(s):  
Seismic Noise ◽  
Subduction Zones ◽  
Seismic Velocity ◽  
Fluid Pressure ◽  
Pore Fluid ◽  
Ambient Seismic Noise ◽  
Pore Fluid Pressure ◽  
Near Surface ◽  
Velocity Reduction ◽  
Pressurized Fluids

In subduction zones, elevated pore fluid pressure, generally linked to metamorphic dehydration reactions, has a profound influence on the mechanical behavior of the plate interface and forearc crust through its control on effective stress. We use seismic noise–based monitoring to characterize seismic velocity variations following the 2012 Nicoya Peninsula, Costa Rica earthquake [Mw(moment magnitude) 7.6] that we attribute to the presence of pressurized pore fluids. Our study reveals a strong velocity reduction (~0.6%) in a region where previous work identified high forearc pore fluid pressure. The depth of this velocity reduction is constrained to be below 5 km and therefore not the result of near-surface damage due to strong ground motions; rather, we posit that it is caused by fracturing of the fluid-pressurized weakened crust due to dynamic stresses. Although pressurized fluids have been implicated in causing coseismic velocity reductions beneath the Japanese volcanic arc, this is the first report of a similar phenomenon in a subduction zone setting. It demonstrates the potential to identify pressurized fluids in subduction zones using temporal variations of seismic velocity inferred from ambient seismic noise correlations.

Interpreting seismic velocity changes observed with ambient seismic noise correlations

2016 ◽  
Vol 4 (3) ◽  
pp. SJ77-SJ85 ◽  
Author(s):  
Gerrit Olivier ◽  
Florent Brenguier
Keyword(s):  
Seismic Noise ◽  
Relative Velocity ◽  
Dynamic Stress ◽  
Seismic Velocity ◽  
Ambient Seismic Noise ◽  
Seismic Velocity Changes ◽  
Velocity Variations ◽  
Velocity Changes ◽  
Pressure Changes

Recent results have shown that crosscorrelating ambient seismic noise recorded in underground mines can successfully extract the seismic Green’s function between sensors. We have revisited an earlier experiment that showed that these virtual seismic sources can be used to measure changes in seismic velocity accurately enough to monitor the short- and long-term influences of a blast in an underground mine. To use this method routinely, it is important to determine the cause of velocity variations in the absence of large dynamic stress perturbations (such as blasts). It also is important to calibrate the seismic velocity changes in terms of known stress changes so the effect of mining activities can be quantified in units that can be used by geotechnical engineers. To this end, we used coda-wave interferometry to measure relative velocity variations during times where no significant blasting or microseismic activity occurred and compared it to atmospheric air pressure changes, temperature variations, and modeled tidal strain. The results indicate that atmospheric air pressure changes have a measurable influence on the long-term seismic velocity variations at depth in the absence of large dynamic stress perturbations. This influence enabled us to determine the sensitivity of the relative velocity changes to stress, where a value of [Formula: see text] was found. This calibration essentially enables us to turn each sensor pair in an underground mine into a stress meter, paving the way for geotechnical engineers to use ambient seismic noise correlations to monitor the evolution of stress and to assess seismic hazard in conjunction with conventional microseismic methods.

Optimization of ambient seismic noise interferometry to monitor groundwater level variations.

2020 ◽  
Author(s):  
Marco Taruselli ◽  
Diego Arosio ◽  
Laura Longoni ◽  
Monica Papini ◽  
Luigi Zanzi
Keyword(s):  
Seismic Noise ◽  
Cross Correlation ◽  
Seismic Velocity ◽  
Time Windows ◽  
Underground Water ◽  
Ambient Seismic Noise ◽  
Correlation Technique ◽  
Noise Interferometry ◽  
The Cross ◽  
Cross Correlation Technique

<p> In this work, we test the cross-correlation of ambient seismic noise method in monitoring underground water variations. Within this perspective we applied the abovementioned technique to study the water table changes occurring both in areas exploited for drinking water needs and inside landslides. Into detail, surveys were carried out in Crépieux-Charmy and Ventasso water catchment fields and in the Cà Lita landslide, respectively. Our aim is to optimize the outcome of the method by studying the effect of different processing steps involved in the computation of the cross-correlation technique. For this purpose, we analyzed the influence of filter types and different time windows length. Additionally, in order to address the problem of localization of the change in the medium the seismic velocity variations have been also derived from limited frequency bandwidths according to the characteristics observed in the signals spectrum. This work has shown the potential of this methodology as a valuable non-destructive toll to accurately describe hydrogeological dynamics. The monitoring system could thus be coupled with the traditional tools to improve the reconstruction of the underground water variations.</p>

scholarly journals Ambient Seismic Noise and Microseismicity Monitoring of a Prone-To-Fall Quartzite Tower (Ormea, NW Italy)

2021 ◽  
Vol 13 (9) ◽  
pp. 1664
Author(s):  
Chiara Colombero ◽  
Alberto Godio ◽  
Denis Jongmans
Keyword(s):  
Seismic Noise ◽  
Seismic Velocity ◽  
Seismic Monitoring ◽  
Geometric Constraints ◽  
Ambient Seismic Noise ◽  
Clear Correlation ◽  
3D Numerical Modeling ◽  
Permanent Displacement ◽  
Resonance Frequencies ◽  
Passive Seismic

Remote sensing techniques are leading methodologies for landslide characterization and monitoring. However, they may be limited in highly vegetated areas and do not allow for continuously tracking the evolution to failure in an early warning perspective. Alternative or complementary methods should be designed for potentially unstable sites in these environments. The results of a six-month passive seismic monitoring experiment on a prone-to-fall quartzite tower are here presented. Ambient seismic noise and microseismicity analyses were carried out on the continuously recorded seismic traces to characterize site stability and monitor its possible irreversible and reversible modifications driven by meteorological factors, in comparison with displacement measured on site. No irreversible modifications in the measured seismic parameters (i.e., natural resonance frequencies of the tower, seismic velocity changes, rupture-related microseismic signals) were detected in the monitored period, and no permanent displacement was observed at the tower top. Results highlighted, however, a strong temperature control on these parameters and unusual preferential vibration directions with respect to the literature case studies on nearly 2D rock columns, likely due the tower geometric constraints, as confirmed by 3D numerical modeling. A clear correlation with the tower displacement rate was found in the results, supporting the suitability of passive seismic monitoring systems for site characterization and early waning purposes.

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