the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Ice plate deformation and cracking revealed by an in-situ distributed acoustic sensing array
Chao Liang
Sidao Ni
Risheng Chu
Feng Bao
Rongbing Lin
Benxin Chi
Abstract. The study of seismic sources and wave propagation in ice plate is helpful to understand the structure, migration, fracture mechanics, mass balance and other processes. However, due to extreme environment, in-situ dense seismic observations are rare and the dynamic changes of the ice plate remain poorly understood. We conduct a seismic experiment with distributed acoustic sensing array on a frozen lake. We excite water vibrations by under-water airgun shots. With an artificial intelligence method, we detected seismic signals including high frequency icequakes and low frequency events. Icequakes cluster along the fractures and correlate with the local temperature variation. The flexural-gravity wave reveals the property of the ice plate. Our study demonstrates the utility of DAS array as an in-situ dense seismic network in illuminating the internal failure process and dynamic deformation of ice plate such as ice shelf, which contributes to understanding and prediction of disintegrations of ice shelves.
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Jun Xie et al.
Status: final response (author comments only)
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RC1: 'Comment on tc-2023-26', Anonymous Referee #1, 02 Apr 2023
The paper presents a DAS experiment in a lake. The seismic data included airgun sources data, and passive signals. The DAS experiment is unique and could provide great DAS experience and research results in the lake to the community.
The writing needs to improve. I am assuming this will be a full technical paper but authors left some of important technical methods and figures in supporting information/appendix.
It’s silly to put something like “consistent with previous studies”. Whenever I read the interesting findings, I expect authors to present their full assessment and analysis, instead of “consistent”.
It may be useful to mention a little information on the instrument and the cable.
Figure 3S is hard to read the picks. What are V1 and V2? Why are they quite different?
“in the and the elongation”
“When some icequakes occurred, the staff also heard the cracking sound, consistent with previous observations (Kavanaugh et al., 2018).” ????
“The number of icequakes does not seem to be associated with AGEs but is rather correlated with the local temperature variation (Fig. 2c), consistent with other studies (e.g., Kavanaugh et al., 2018).”
AI accuracy for AGE is 73% and for icequake 62.8%. These are very low. Since AGE are active sources, the groundtruth is known. This accuracy is not satisfied. Is AI model better than STA/LTA?
I don’t understand the bias errors in the location of 10 hammer shots. Again, this location is known and should be recovered very accurate with ignorable errors. It means that the physics parameters (what are they? Authors didn’t specify these) can be determined from the hammer shots.
“This dispersion curve has the canonical trait of a special guided wave along a suspending ice shelf driven by the interplay of ice plate flexure and gravity, namely the Flexural-Gravity Wave” I don’t understand this. Please illustrate more here!
What’s the uncertainty of 10 GPa?
The section of using PhaseNet to detect events is very random. If the YOLO is good with the accuracy, why should I care about the PhaseNet results? I want to ask, what’s the main purpose of this research?
“using optical methods” this is confusing. What are optical methods? Including DAS?
The data availability statement “All raw data can be provided by the corresponding authors upon request.” Is reasonable for the journal?
Citation: https://doi.org/10.5194/tc-2023-26-RC1 - AC1: 'Reply on RC1', Jun Xie, 13 Jun 2023
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AC2: 'Reply on RC1', Jun Xie, 13 Jun 2023
Publisher’s note: this comment is a copy of AC1 and its content was therefore removed.
Citation: https://doi.org/10.5194/tc-2023-26-AC2
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RC2: 'Comment on tc-2023-26', Anonymous Referee #2, 06 May 2023
This manuscript describes a DAS experiment conducted on a frozen lake, with active airgun shots fired below the ice. In addition to the airgun-excited waves, two additional classes of events could be detected: (1) high-frequency waves that most likely originate from ice quakes caused by thermal expansion, and (2) a smaller number of low-frequency events that are excited by water waves and can be used to constrain the elastic properties of the ice.
The manuscript is logically structured and the data are certainly interesting. Nevertheless, there are several important issues that should be addressed prior to publication of the manuscript.
LANGUAGE
My most important criticism is the unacceptable level of the English. While the meaning of most sentences can be guessed, part of the content can simply not be understood. This is absolutely not about correcting a few typos. Almost every single sentence should be corrected or rewritten.
BEYOND THE OBVIOUS
While the data are, as previously mentioned, interesting, it is unclear how they go beyond the obvious. Large numbers of quasi-randomly distributed ice quakes caused by diurnal thermal expansion are exactly what one would expect. The same holds for water-wave-induced events at lower frequency. That the latter can be used to constrain ice properties has been known at least since the 1950s. In summary, the authors should explain much more explicitly why this is science beyond the obvious that should be published in a journal like 'The Cryosphere'.
BROADER IMPLICATIONS
Along similar lines, it is unclear what the broader implications of this work are. For example, what is the transferable insight that we gain? Why is this potentially more than just a study of one among very many ice sheets?
COMPARISON
One of the authors' major conclusions is that DAS offers new opportunities that conventional instruments may not offer. However, this claim is not at all supported. The authors compare to the recordings of an on-shore seismometer, which is not only further away from the ice quakes than the DAS array but also naturally records lower amplitudes than instruments on the floating ice sheet. (For example, much of the energy will not even make it from the fluid into the solid.) Hence, the authors' claim really rests on an unfair comparison of apples and oranges.
Citation: https://doi.org/10.5194/tc-2023-26-RC2 - AC3: 'Reply on RC2', Jun Xie, 13 Jun 2023
Jun Xie et al.
Jun Xie et al.
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