Dynamical evolution of the seismic coda wave increments during the 2011-2012 Santorini's caldera unrest. A Non-Extensive Statistical Physics approach.

Mapping Intimacies ◽

10.5194/egusphere-egu2020-8190 ◽

2020 ◽

Author(s):

Theodoros Aspiotis ◽

Ioannis Koutalonis ◽

Georgios Michas ◽

Filippos Valianatos

Keyword(s):

Statistical Physics ◽

Distribution Functions ◽

Coda Waves ◽

Coda Wave ◽

Tectonic Activity ◽

Volcanic Complex ◽

Dynamical Structure ◽

Gaussian Shape ◽

Caldera Unrest ◽

Seismic Coda

Santorini's caldera being unrest during 2011-2012, led several studies to raise the important question of whether seismicity is associated with an impending and potential volcanic eruption or it solely relieves the accumulated tectonic energy. In the present work we study seismic coda waves generated by local earthquake events prior, during and after the seismic crisis that occurred within the caldera area. Coda waves are interpreted as scattered seismic waves generated by heterogeneities within the Earth, i.e. by faults, fractures, velocity and/or density boundaries and anomalies, etc. In particular, we utilize the three components of the seismograms recorded by three seismological stations on the island of Santorini and estimate the duration of the coda waves by implementing a three step procedure that includes the signal-to-noise ratio, the STA/LTA method and the short time Fourier transform. The final estimation was verified or reestimated manually due to the existent ambient seismic noise. Due to the nature and the path complexity of the coda waves and towards achieving a unified framework for the study of the immerse geo-structural seismotectonic complexity of the Santorini volcanic complex, we use Non-Extensive Statistical Physics (NESP) to study the probability distribution functions (pdfs) of the increments of seismic coda waves. NESP forms a generalization of the Boltzmann-Gibbs statistical mechanics, that has been extensively used for the analysis of semi-chaotic systems that exhibit long-range interactions, memory effects and multi-fractality. The analysis and results demonstrate that the seismic coda waves increments deviate from the Gaussian shape and their respective pdfs could adequately be described and processed by the q-Gaussian distribution. Furthermore and in order to investigate the dynamical structure of the volcanic-tectonic activity, we estimate the q-indices derived from the pdfs of the coda wave time series increments during the period 2009 - 2014 and present their variations as a function of time and as a function of the local magnitude (ML) of the events prior, during and after the caldera unrest. &#160; &#160;Acknowledgments.&#160;We acknowledge support by the project &#8220;HELPOS &#8211; Hellenic System for Lithosphere Monitoring&#8221; (MIS 5002697) which is implemented under the Action &#8220;Reinforcement of the Research and Innovation Infrastructure&#8221;, funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece & European Union (ERDF)

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Seismic coda Q and scaling law of the source spectra at the Aeolian Islands, southern Italy

Bulletin of the Seismological Society of America ◽

10.1785/bssa0730010097 ◽

1983 ◽

Vol 73 (1) ◽

pp. 97-108

Author(s):

E. Del Pezzo ◽

F. Ferulano ◽

A. Giarrusso ◽

M. Martini

Keyword(s):

Southern Italy ◽

Scaling Law ◽

Coda Wave ◽

Corner Frequency ◽

Volcanic Complex ◽

Coda Q ◽

Aeolian Islands ◽

Scaling Properties ◽

Linear Pattern ◽

Seismic Coda

abstract The model developed by Aki and Chouet for the coda wave generation and propagation has been used to calculate the quality factor Q for the zone of the Aeolian Islands, southern Italy, in the frequency range of 1 to 12 Hz, and the scaling properties of the seismic spectrum in the magnitude range of 0.4 to 4.7. The Q found for the Aeolian area has a frequency dependence of the form Q = qfv. The absolute values of Q seem to be dependent on the station and location of the seismic events, confirming the strong lateral heterogeneities in the geological structure beneath the Aeolian Arc. A temporal variation has been noted in the Q calculated at Vulcano station (VPL) in a period of 3 weeks soon after the occurrence of a main shock of ML = 5.5 located near the station. The scaling behavior of this sequence is similar to that obtained in two areas of California and one portion of Japan, with a corner frequency that remains constant with an increasing seismic moment between magnitudes 1 and 4. It differs substantially from the scaling properties of the Hawaian earthquakes that show a linear pattern, without an increase of the stress drop with magnitude. The fact that Vulcano is an active volcano seems not to influence the scaling properties of the seismic sequence localized very near it. It probably indicates that the aftershocks used for calculating the scaling law are generated out of the volcanic complex Lipari-Vulcano, in a zone with a good capability of accumulating the stress.

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Simulation of seismic wave scattering for the computation of probabilistic coda-wave sensitivity kernels

10.5194/egusphere-egu2020-5408 ◽

2020 ◽

Author(s):

Tuo Zhang ◽

Christoph Sens-Schönfelder

Keyword(s):

Wave Velocity ◽

Wave Scattering ◽

Random Medium ◽

Coda Waves ◽

Coda Wave ◽

Small Scale ◽

Model Parameters ◽

S Wave ◽

Seismic Coda ◽

Wave Sensitivity

Scattered seismic coda waves are frequently used to characterize small scale medium heterogeneities, intrinsic attenuation or temporal changes of wave velocity. Spatial variability of these properties raises questions about the spatial sensitivity of seismic coda waves. Especially the continuous monitoring of medium perturbations using ambient seismic noise led to a demand for approaches to image perturbations observed with coda waves. An efficient approach to localize the property variations in the medium is to invert the observations from different source-receiver combinations and different lapse times in the coda for the location of the perturbations. The key of such an inversion is calculating the coda-wave sensitivity kernels which describe the connection between observations and the perturbation. Most discussions of sensitivity kernels use the acoustic approximation and assume wave propagation in the diffusion regime.We model 2-D &#160;elastic multiple nonisotropic scattering in a random medium with spatially variable heterogeneity and attenuation. The Monte Carlo method is used to numerically solve the radiative transfer equation that describes the wave scattering process here. Recording of the specific intensity of the wavefield I(r,n,t) which contains the complete information about the energy at position r at time t with the propagation direction n allows us to calculate sensitivity kernels according to rigorous theoretical derivations. We investigate sensitivity kernels that describe the relationships between changes of the model parameters P- and S-wave velocity, P- and S-wave attenuation, and the strength of fluctuation on the one hand and the observables envelope amplitude, travel time changes and decorrelation on the other hand. These sensitivity kernels reflect the effect of the spatial variations of medium properties on wavefield. Our work offers a direct approach to compute these new expressions and adapt them to spatially variable heterogeneities. The sensitivity kernels we derived are the first step in the development of an inversion approach based on coda waves.

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Sensitivity kernels for static and dynamic tomography of scattering and absorbing media with elastic waves: a probabilistic approach

Geophysical Journal International ◽

10.1093/gji/ggab048 ◽

2021 ◽

Vol 225 (3) ◽

pp. 1824-1853

Author(s):

Tuo Zhang ◽

Christoph Sens-Schönfelder ◽

Ludovic Margerin

Keyword(s):

Energy Density ◽

Wave Velocity ◽

Probabilistic Approach ◽

Coda Waves ◽

Isotropic Scattering ◽

Coda Wave ◽

Small Scale ◽

Practical Calculation ◽

S Wave ◽

Seismic Coda

SUMMARY Scattered seismic coda waves are frequently used to characterize small scale medium heterogeneities, intrinsic attenuation or temporal changes of wave velocity. Spatial variability of these properties raises questions about the spatial sensitivity of seismic coda waves. Especially the continuous monitoring of medium perturbations using ambient seismic noise led to a demand for approaches to image perturbations observed with coda waves. An efficient approach to localize spatial and temporal variations of medium properties is to invert the observations from different source–receiver combinations and different lapse times in the coda for the location of the perturbations. For such an inversion, it is key to calculate the coda-wave sensitivity kernels which describe the connection between observations and the perturbation. Most discussions of sensitivity kernels use the acoustic approximation in a spatially uniform medium and often assume wave propagation in the diffusion regime. We model 2-D multiple non-isotropic scattering in a random elastic medium with spatially variable heterogeneity and attenuation using the radiative transfer equations which we solve with the Monte Carlo method. Recording of the specific energy density of the wavefield that contains the complete information about the energy density at a given position, time and propagation direction allows us to calculate sensitivity kernels according to rigorous theoretical derivations. The practical calculation of the kernels involves the solution of the adjoint radiative transport equations. We investigate sensitivity kernels that describe the relationships between changes of the model in P- and S-wave velocity, P- and S-wave attenuation and the strength of fluctuation on the one hand and seismogram envelope, traveltime changes and waveform decorrelation as observables on the other hand. These sensitivity kernels reflect the effect of the spatial variations of medium properties on the wavefield and constitute the first step in the development of a tomographic inversion approach for the distribution of small-scale heterogeneity based on scattered waves.

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Phase Statistics of Seismic Coda Waves

Physical Review Letters ◽

10.1103/physrevlett.102.248501 ◽

2009 ◽

Vol 102 (24) ◽

Cited By ~ 11

Author(s):

D. Anache-Ménier ◽

B. A. van Tiggelen ◽

L. Margerin

Keyword(s):

Coda Waves ◽

Seismic Coda

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Coda Waves for Health Monitoring of Composites Under Low-Velocity Impact

10.1115/qnde2021-75297 ◽

2021 ◽

Author(s):

Subal Sharma ◽

Vinay Dayal

Keyword(s):

Ultrasonic Waves ◽

Coda Waves ◽

Low Velocity Impact ◽

Coda Wave ◽

Low Velocity ◽

Fibrous Composite Material ◽

Velocity Impact ◽

Isotropic Composite ◽

The Impact ◽

Impact Damages

Abstract Coda waves have been shown to be sensitive to lab-controlled defects such as very small holes in fibrous composite material. In the real world, damages are subtler and more irregular. The main objective of this work is to investigate coda wave capability to detect low-velocity impact damages. The emphasis is to detect the presence of barely visible impact damages using ultrasonic waves. Detection of incipient damage state is important as it will grow over the life of the structure. Differential features, previously used in similar work, have been utilized to detect realistic impact damages on carbon fiber composites. Quasi-isotropic composite laminates were subjected to low-velocity impact energy ranging from 2J to 4.5J. Two differential features reported could be used detect the presence of damage. It is also observed that ply orientation can be a deterministic factor for indicating damages. The size and shape of the impact damage has been characterized using ultrasonic C-scans. Results indicate that coda waves can be used for the detection of damage due to low-velocity impact.

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Limit distribution functions of systems with many-particle interaction in classical statistical physics

Theoretical and Mathematical Physics ◽

10.1007/bf01037649 ◽

1975 ◽

Vol 25 (1) ◽

pp. 1029-1035 ◽

Cited By ~ 6

Author(s):

G. I. Nazin

Keyword(s):

Limit Distribution ◽

Statistical Physics ◽

Particle Interaction ◽

Distribution Functions

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Attenuation of Coda Waves in the Central Region of the Gulf of California, México

Geofísica Internacional ◽

10.22201/igeof.00167169p.2017.56.2.1761 ◽

2017 ◽

Vol 56 (2) ◽

Author(s):

Héctor E. Rodríguez-Lozoya ◽

Tonatiuh Domínguez R. ◽

Luis Quintanar Robles ◽

Armando Aguilar Meléndez ◽

Héctor E. Rodríguez-Leyva ◽

...

Keyword(s):

Central Region ◽

Gulf Of California ◽

Single Scattering ◽

Coda Waves ◽

Tectonic Activity ◽

S Wave ◽

A Value ◽

Wave Travel ◽

Coda Attenuation ◽

North And South

Coda waves were analyzed from events recorded by NARS seismic network deployed along both margins of the Gulf of California, Mexico, to estimate coda attenuation Qc. Sato’s (1977) single scattering model was used for a coda window of 20 to 25 s beginning at twice the S-wave travel time. Events recorded from 2003 to 2007 located in the central region of the Gulf of California were analyzed. Source-to-receiver distances are between 40 and 500 km. Assuming a power law of the form QC (f) = QO f a, QC values were averaged and a value of QO = 83Â±3 and a frequency-dependence Î± value of 1.06Â±0.03 in the frequency range from 1 to 7 Hz was obtained. QO value and the high frequency dependency agree with the values of other regions characterized by a high tectonic activity. Based on source-station distribution two subregions (north and south) were defined. QC values were calculated and correlated with tectonics and morphology of each area. The observed higher attenuation in the south region can be attributed to the fact that south region is more fractured since the greater earthquakes occur in central to south Gulf of California and the oceanic crust is reported to be thinner in the southern region.

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

10.5194/nhess-2021-205 ◽

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.

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