Source Parameters of Laboratory Acoustic Emission Events Estimated From the Coda of Waveforms

We develop a method to estimate relative seismic moments M0 and corner frequencies fc of acoustic emission events recorded in laboratory experiments from amplitude spectra of signal's coda composed of reverberated and scattered waves. This approach has several advantages with respect to estimat...

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Bibliographic Details
Published in:Journal of geophysical research. Solid earth 2024-04, Vol.129 (4), p.n/a
Main Authors: Kartseva, Tatiana I., Shapiro, Nikolai M., Patonin, Andrey V., Shikhova, Natalia M., Smirnov, Vladimir B., Ponomarev, Alexander V.
Format: Article
Language:English
Subjects:
Acoustic emission
Acoustic waves
Acoustics
Axial loads
coda signal
Crystal defects
Earth Sciences
Earthquake damage
Earthquakes
Emission analysis
Experiments
External pressure
Fractures
Fracturing
Granite
Laboratories
Laboratory experimentation
Laboratory experiments
Massifs
Parameters
Pressure
rock physics
Rocks
Sandstone
Scaling
Sciences of the Universe
Sediment samples
Sedimentary rocks
Seismic activity
Seismicity
Seismology
Similarity
Sound waves
source parameters
Spectra
spectral ratio
Stone
stress‐drop
Tectonics
Waveforms
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Summary:We develop a method to estimate relative seismic moments M0 and corner frequencies fc of acoustic emission events recorded in laboratory experiments from amplitude spectra of signal's coda composed of reverberated and scattered waves. This approach has several advantages with respect to estimations from direct waves that are often clipped and also are difficult to separate in experiments performed on small samples. Also, inversion of the coda spectra does not require information about the source locations and mechanisms. We use the developed method to analyze the data of two experiments: (a) on granite from the Voronezh crystal massif and (b) on Berea sandstone. The range of absolute corner frequencies estimated in both experiments is around 70 − −700 kHz. The range of relative seismic moments covers 103.5. The relation between fc and M0 observed on the first stages of both experiments, consisted of increasing isotropic confining pressure, approximately follow M0∼fc−3 ${M}_{0}\sim {f}_{c}^{-3}$ scaling and the b‐value of the Gutenberg‐Richter distribution was found close to 1. This can be interpreted as rupturing of preexisting material defects with a nearly constant stress‐drop and has a similarity with observations of “natural” earthquakes. Deviations from this “earthquake‐like” behavior observed after applying axial loading and initiation of sample damaging can be interpreted as changes in stress‐drop. Lower stress‐drops prevail for sandstone and higher for granite sample respectively that can be related to the strength of corresponding material. Plain Language Summary Earthquakes generation mechanisms and conditions favoring their occurrence are still debated. Inability to observe these processes in–situ and long lasting earthquake preparation period favor using laboratory experiments to verify quickly the adequacy of proposed hypotheses. Fracturing of small rock samples with high pressures and recording acoustic waves from their micro‐fractures is among them. In most cases, the laboratory acoustic emission (AE) is analyzed and compared to natural seismicity statistically, demonstrating similar Gutenberg‐Richter power‐law magnitude distribution. More advanced analyses can include source characteristics (corner frequencies, seismic moments, and stress‐drops), responsible for the source size, forces acting there and stress changes. Ensembles of these characteristics can give ideas on the common generation mechanisms. In laboratory, several technical limi
ISSN:2169-9313
2169-9356
DOI:10.1029/2023JB028313