scholarly journals Hanging glacier monitoring with icequake repeaters and seismic coda wave interferometry: a case study of the Eiger hanging glacier

2021 ◽  
Author(s):  
Małgorzata Chmiel ◽  
Fabian Walter ◽  
Lukas Preiswerk ◽  
Martin Funk ◽  
Lorenz Meier ◽  
...  
Keyword(s):  
Large Scale ◽  
Wave Attenuation ◽  
Seismic Velocity ◽  
Swiss Alps ◽  
Coda Wave ◽  
Diurnal Cycles ◽  
Ice Surface ◽  
Novel Approach ◽  
Seismic Coda ◽  
Coda Wave Interferometry

Abstract. Driven by the force of gravity, hanging glacier instabilities can lead to catastrophic rupture events. Reliable forecasting remains a challenge as englacial damage leading to large-scale failure is masked from modern sensing technology focusing on the ice surface. The Eiger hanging glacier, located in the Swiss Alps, was intensely monitored between April and August 2016 before a moderate 15,000 m3 break-off event from the ice cliff. Among different instruments, such as an automatic camera and interferometric radar, four 3-component seismometers were installed on the glacier. A single seismometer operated throughout the whole monitoring period. It recorded over 200,000 repeating icequakes showing strong englacial seismic coda waves. We propose a novel approach for hanging glacier monitoring by combining repeating icequake analysis, coda wave interferometry, and attenuation measurements. Our results show a seasonal 0.1 % decrease in relative englacial seismic velocity dv/v and an increase in coda wave attenuation Qc−1 (Qc decreases from ~50 to ~30). Comparison of dv/v and Qc with air temperature suggests that these changes are driven by a seasonal increase in the glacier’s ice and firn pack temperature that might affect the top 20 m of the glacier. Diurnal cycles of Qc−1, repeating icequake activity, and the velocity of the glacier front shift from cosinusoidal to sinusoidal variations under the presence of meltwater. The proposed approach extends the monitoring of the hanging glacier beyond the ice surface and allows for a better understanding of the glacier’s response to time-dependent external forcing, which is an important step towards improved break-off forecasting systems.

Investigation of ambient noise seismological methods on a bridge model

2021 ◽  
Author(s):  
Chun-Man Liao ◽  
Franziska Mehrkens ◽  
Celine Hadziioannou ◽  
Ernst Niederleithinger
Keyword(s):  
Wave Propagation ◽  
Large Scale ◽  
Seismic Velocity ◽  
Measurement Data ◽  
Correlation Coefficients ◽  
Coda Wave ◽  
Velocity Change ◽  
Promising Tool ◽  
Bridge Model ◽  
Noise Measurements

<p>The aim of this work is to investigate the application of seismological noise-based monitoring for bridge structures. A large-scale two-span concrete bridge model with a build-in post-tensioning system, which is exposed to environmental conditions, is chosen as our experimental test structure. Ambient seismic noise measurements were carried out under different pre-stressed conditions. Using the seismic interferometry technique, which is applied to the measurement data in the frequency domain, we reconstruct waveforms that relate to wave propagation in the structure. The coda wave interferometry technique is then implemented by comparing two waveforms recorded in two pre-stress states. Any relative seismic velocity changes are identified by determining the correlation coefficients and reveal the influence of the pre-stressing force. The decrease of the wave propagation velocity indicates the loss of the pre-stress and weakening stiffness due to opening or event extension of cracks. We conclude that the seismological methods used to estimate velocity change can be a promising tool for structural health monitoring of civil structures.</p>

Seasonal cycles of seismic velocity variations detected using coda wave interferometry at Fogo volcano, São Miguel, Azores, during 2003–2004

2009 ◽  
Vol 181 (3-4) ◽  
pp. 231-246 ◽  
Author(s):  
Francesca Martini ◽  
Christopher J. Bean ◽  
Gilberto Saccorotti ◽  
Fatima Viveiros ◽  
Nicolau Wallenstein
Keyword(s):  
Seismic Velocity ◽  
Coda Wave ◽  
Seasonal Cycles ◽  
Velocity Variations ◽  
Coda Wave Interferometry ◽  
Fogo Volcano

Stress drop estimates for some aftershocks of the Ometepec, Guerrero, Mexico, earthquake of June 7, 1982

1987 ◽  
Vol 24 (8) ◽  
pp. 1727-1733 ◽  
Author(s):  
Cecilio J. Rebollar ◽  
Rosa M. Alvarez
Keyword(s):  
Stress Drop ◽  
Wave Attenuation ◽  
Seismic Energy ◽  
Coda Wave ◽  
Apparent Stress ◽  
Radiated Seismic Energy ◽  
Seismic Coda ◽  
Seismic Quality Factor ◽  
Single Station ◽  
Stress Drops

Brune's stress drop, apparent stress, and arms stress drop are estimated at a single station for 25 aftershocks of the Ometepec earthquakes (Ms = 6.9 and Ms = 7.0). The arms stress drops and apparent stresses are systematically smaller than Brune's stress drops. Stress drops from the root mean square of acceleration and apparent stress range from 0.01 to 10.2 bars (1 bar = 100 kPa) except for two values (21.4 and 33.0 bars). On the other hand, Brune's stress drops range from 0.6 to 239 bars. Seismic moments ranging from 0.5 × 1019 to 289 × 1019 dyn∙cm (1 dyn∙cm = 10 μN∙cm) were estimated for events with coda magnitudes between 0.6 and 2.2. Values of radiated seismic energy calculated by integration of the displacement spectra range from 2.5 × 1012 to 2.3 × 1016 dyn∙cm. The fmax values lie between 16 and 30 Hz. Seismic coda wave attenuation measured on narrow band-pass-filtered seismograms show a linear dependence of the seismic quality factor of the form [Formula: see text] in the range of frequencies from 3 to 24 Hz.

Variation of Seismic Coda Wave Attenuation in the Garhwal Region, Northwestern Himalaya

2011 ◽  
Vol 169 (1-2) ◽  
pp. 71-88 ◽  
Author(s):  
Jayant N. Tripathi ◽  
Priyamvada Singh ◽  
Mukat L. Sharma
Keyword(s):  
Wave Attenuation ◽  
Coda Wave ◽  
Seismic Coda ◽  
Coda Wave Attenuation ◽  
Garhwal Region

scholarly journals Detection of Multiple Cracks in Four-Point Bending Tests Using the Coda Wave Interferometry Method

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 1986 ◽  
Author(s):  
Xin Wang ◽  
Joyraj Chakraborty ◽  
Antoine Bassil ◽  
Ernst Niederleithinger
Keyword(s):  
Fiber Optics ◽  
Large Scale ◽  
Early Stage ◽  
Image Correlation ◽  
Bending Test ◽  
Coda Wave ◽  
Multiple Cracks ◽  
Rc Structures ◽  
Four Point Bending ◽  
Coda Wave Interferometry

The enlargement of the cracks outside the permitted dimension is one of the main causes for the reduction of service life of Reinforced Concrete (RC) structures. Cracks can develop due to many causes such as dynamic or static load. When tensile stress exceeds the tensile strength of RC, cracks appear. Traditional techniques have limitations in early stage damage detection and localisation, especially on large-scale structures. The ultrasonic Coda Wave Interferometry (CWI) method using diffuse waves is one of the most promising methods to detect subtle changes in heterogeneous materials, such as concrete. In this paper, the assessment of the CWI method applied for multiple cracks opening detection on two specimens based on four-point bending test is presented. Both beams were monitored using a limited number of embedded Ultrasonic (US) transducers as well as other transducers and techniques (e.g., Digital Image Correlation (DIC), LVDT sensors, strain gauges, and Fiber Optics Sensor (FOS)). Results show that strain change and crack formation are successfully and efficiently detected by CWI method even earlier than by the other techniques. The CWI technique using embedded US transducers is undoubtedly a feasible, efficient, and promising method for long-term monitoring on real infrastructure.

scholarly journals Source Separation and Medium Change of Contained Chemical Explosions from Coda Wave Interferometry

2021 ◽  
Vol 1 (1) ◽  
pp. 3-10
Author(s):  
Sean R. Ford ◽  
William R. Walter
Keyword(s):  
Coda Wave ◽  
Velocity Perturbation ◽  
Spherical Region ◽  
Seismic Coda ◽  
Chemical Explosions ◽  
Medium Change ◽  
Physics Experiment ◽  
Coda Wave Interferometry ◽  
Source Physics ◽  
Chemical Explosion

Abstract Differences in the seismic coda of neighboring events can be used to investigate source location offsets and medium change with coda wave interferometry (CWI). We employ CWI to infer the known relative location between two chemical explosions in Phase I of the Source Physics Experiment (SPE). The inferred displacement between the first, SPE-1, and second, SPE-2, chemical explosion is between 6 and 18 m, with an expectation of 9.2 m, where the known separation is close to 9.4 m. We also employ CWI to find any velocity perturbation due to damage from SPE-2, by comparing its coda with the collocated third SPE chemical explosion, SPE-3. We find that damage due to SPE-2 must be confined to a spherical region with radius less than 10 m and velocity perturbation less than 25%.

Multiplet Based Time Lapse Velocity Changes Prior to the 2018 Eruption of Sierra Negra Volcano, Galapagos Island Observed with Coda Wave Interferometry

2020 ◽  
Author(s):  
Mariantonietta Longobardi ◽  
James Grannel ◽  
Christopher Bean ◽  
Andrew Bell ◽  
Mario Ruiz
Keyword(s):  
Wave Velocity ◽  
Seismic Wave ◽  
Seismic Velocity ◽  
Time Lapse ◽  
Coda Wave ◽  
Seismic Wave Velocity ◽  
Galapagos Island ◽  
Velocity Changes ◽  
Coda Wave Interferometry ◽  
Sierra Negra Volcano

<p align="justify"><span>Changes in external stress state and fluid content alter the mechanical properties of an geological media. </span><span>Variations in seismic wave velocity can be used as proxies for changes in stress the onset of mechanical demage and/or possible fluid ingression. Temporal variations in seismic wave velocity have previously been monitored and observed prior to volcanic eruptions. In the absence of additional constraints related to stress or fluid changes on the volcano, these pre-eruptive changes are difficult to interpret and hence the causes of them are often not well understood. </span><span>In this study, Coda Wave Interferometry (CWI) is used to measure time-lapse changes in seismic velocity on seismic multiplets (repeating similar earthquakes). In particular, we focus our analysis on using this technique to calculate the velocity changes on the data recorded prior to the 2018 eruption of Sierra Negra volcano, Galapagos Island.</span> <span>On 26th June 2018 at 09:15 UTC, a magnitude 5.3 earthquake occurred near the south-west caldera rim and an intense seismic swarm started around 17:15 UTC. Seismic tremor dominated at about 19:45 UTC, which marked the onset of the eruption. </span><span>A very large seismicity sequence preceded the eruption. The pricise relationship between the magnitude 5.3 event and the eruption is not fully constraind. Here we search for multiplets in order to achieve high time resolution velocity change information in the hours between the large earthquake and the eruption. </span><span>Our aim is to understand whether changes in seismic velocity measured with CWI on multiplets method provide new insight into the physical processes related to the eruption.</span></p><p align="justify"><br><br></p>

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