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.

scholarly journals Noise-based ballistic wave passive seismic monitoring. Part 1: body waves

2020 ◽  
Vol 221 (1) ◽  
pp. 683-691 ◽  
Author(s):  
F Brenguier ◽  
R Courbis ◽  
A Mordret ◽  
X Campman ◽  
P Boué ◽  
...  
Keyword(s):  
Seismic Velocity ◽  
Noise Source ◽  
Seismic Monitoring ◽  
Body Waves ◽  
P Wave ◽  
New Technique ◽  
Apparent Velocity ◽  
Near Surface ◽  
Velocity Increase ◽  
Passive Seismic

SUMMARY Unveiling the mechanisms of earthquake and volcanic eruption preparation requires improving our ability to monitor the rock mass response to transient stress perturbations at depth. The standard passive monitoring seismic interferometry technique based on coda waves is robust but recovering accurate and properly localized P- and S-wave velocity temporal anomalies at depth is intrinsically limited by the complexity of scattered, diffracted waves. In order to mitigate this limitation, we propose a complementary, novel, passive seismic monitoring approach based on detecting weak temporal changes of velocities of ballistic waves recovered from seismic noise correlations. This new technique requires dense arrays of seismic sensors in order to circumvent the bias linked to the intrinsic high sensitivity of ballistic waves recovered from noise correlations to changes in the noise source properties. In this work we use a dense network of 417 seismometers in the Groningen area of the Netherlands, one of Europe's largest gas fields. Over the course of 1 month our results show a 1.5 per cent apparent velocity increase of the P wave refracted at the basement of the 700-m-thick sedimentary cover. We interpret this unexpected high value of velocity increase for the refracted wave as being induced by a loading effect associated with rainfall activity and possibly canal drainage at surface. We also observe a 0.25 per cent velocity decrease for the direct P-wave travelling in the near-surface sediments and conclude that it might be partially biased by changes in time in the noise source properties even though it appears to be consistent with complementary results based on ballistic surface waves presented in a companion paper and interpreted as a pore pressure diffusion effect following a strong rainfall episode. The perspective of applying this new technique to detect continuous localized variations of seismic velocity perturbations at a few kilometres depth paves the way for improved in situ earthquake, volcano and producing reservoir monitoring.

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 Application of multichannel Wiener filters to the suppression of ambient seismic noise in passive seismic arrays

2008 ◽  
Vol 27 (2) ◽  
pp. 232-238 ◽  
Author(s):  
J. Wang ◽  
F. Tilmann ◽  
R. S. White ◽  
H. Soosalu ◽  
P. Bordoni
Keyword(s):  
Seismic Noise ◽  
Ambient Seismic Noise ◽  
Seismic Arrays ◽  
Wiener Filters ◽  
Passive Seismic

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.

scholarly journals A novel horizontal to vertical spectral ratio approach in a wired structural health monitoring system

2014 ◽  
Vol 3 (2) ◽  
pp. 145-165 ◽  
Author(s):  
F. P. Pentaris
Keyword(s):  
Structural Health Monitoring ◽  
Resonance Frequency ◽  
Health Monitoring ◽  
Seismic Noise ◽  
Ambient Seismic Noise ◽  
Building Vulnerability ◽  
Structural Health ◽  
Resonance Frequencies ◽  
University Buildings ◽  
Hvsr Technique

Abstract. This work studies the effect ambient seismic noise can have on building constructions, in comparison with the traditional study of strong seismic motion in buildings, for the purpose of structural health monitoring. Traditionally, engineers have observed the effect of earthquakes on buildings by usage of seismometers at various levels. A new approach is proposed in which acceleration recordings of ambient seismic noise are used and horizontal to vertical spectra ratio (HVSR) process is applied, in order to determine the resonance frequency of movement due to excitation of the building from a strong seismic event. The HVSR technique is widely used by geophysicists to study the resonance frequency of sediments over bedrock, while its usage inside buildings is limited. This study applies the recordings inside two university buildings attached to each other, but with different construction materials and different years of construction. Also there is HVSR application in another much older building, with visible cracks in its structure. Sensors have been installed on every floor of the two university buildings, and recordings have been acquired both of ambient seismic noise and earthquakes. Resonance frequencies for every floor of every building are calculated, from both noise and earthquake records, using the HVSR technique for the ambient noise data and the receiver function (RF) for the earthquake data. Differential acceleration drift for every building is also calculated, and there is correlation with the vulnerability of the buildings. Results indicate that HVSR process on acceleration data proves to be an easy, fast, economical method for estimation of fundamental frequency of structures as well as an assessment method for building vulnerability estimation. Comparison between HVSR and RF technique shows an agreement at the change of resonance frequency as we move to higher floors.

scholarly journals Modal sensitivity of rock glaciers to elastic changes from spectral seismic noise monitoring and modeling

2021 ◽  
Vol 15 (2) ◽  
pp. 501-529
Author(s):  
Antoine Guillemot ◽  
Laurent Baillet ◽  
Stéphane Garambois ◽  
Xavier Bodin ◽  
Agnès Helmstetter ◽  
...  
Keyword(s):  
Elastic Properties ◽  
Seasonal Pattern ◽  
Porous Matrix ◽  
Seismic Monitoring ◽  
Seismic Velocities ◽  
Resonance Frequencies ◽  
Passive Seismic ◽  
Rock Glaciers ◽  
Poroelastic Model ◽  
Seismic Networks

Abstract. Among mountainous permafrost landforms, rock glaciers are mostly abundant in periglacial areas, as tongue-shaped heterogeneous bodies. Passive seismic monitoring systems have the potential to provide continuous recordings sensitive to hydro-mechanical parameters of the subsurface. Two active rock glaciers located in the Alps (Gugla, Switzerland, and Laurichard, France) have been instrumented with seismic networks. Here, we analyze the spectral content of ambient noise to study the modal sensitivity of rock glaciers, which is directly linked to the system's elastic properties. For both sites, we succeed in tracking and monitoring resonance frequencies of specific vibrating modes of the rock glaciers over several years. These frequencies show a seasonal pattern characterized by higher frequencies at the end of winters and lower frequencies in warm periods. We interpret these variations as the effect of the seasonal freeze–thawing cycle on elastic properties of the medium. To assess this assumption, we model both rock glaciers in summer, using seismic velocities constrained by active seismic acquisitions, while bedrock depth is constrained by ground-penetrating radar surveys. The variations in elastic properties occurring in winter due to freezing were taken into account thanks to a three-phase Biot–Gassmann poroelastic model, where the rock glacier is considered a mixture of a solid porous matrix and pores filled by water or ice. Assuming rock glaciers to be vibrating structures, we numerically compute the modal response of such mechanical models by a finite-element method. The resulting modeled resonance frequencies fit well the measured ones over seasons, reinforcing the validity of our poroelastic approach. This seismic monitoring allows then a better understanding of the location, intensity and timing of freeze–thawing cycles affecting rock glaciers.

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