the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Seismic attenuation in Antarctic firn
Stefano Picotti
José M. Carcione
Mauro Pavan
Abstract. We estimate the P- and S-wave seismic attenuation in polar firn from spectral analysis of diving-wave first-breaks of three-component active-source seismic observations carried out in 2010 on the Whillans Ice Stream (WIS), a fast-flowing ice stream in West Antarctica. The resulting quality factors are then successfully modeled using a rock-physics theory of wave propagation which combines White's mesoscopic attenuation theory of interlayer flow with that of Biot/squirt flow. The first theory describes an equivalent viscoelastic medium of a stack of two thin alternating porous layers of thickness much larger than the pore size but smaller than the wavelength. On the other hand, in the so-called Biot/squirt-flow model, there are two loss mechanisms, namely the Biot global-flow one and local flow from fluid-filled micro-cracks (or grain contacts) to the pore space and back, where the former is dominant over the latter. The fluid saturating the pores is assumed to be fluidized snow, which is defined as a mixture of snow particles and air, like powder, having zero rigidity modulus.
Stefano Picotti et al.
Status: open (until 14 Jun 2023)
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RC1: 'Comment on tc-2023-19', Rolf Sidler, 05 Mar 2023
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Please see attached PDF file.
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AC1: 'Reply on RC1', Stefano Picotti, 15 Mar 2023
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AC1: 'Reply on RC1', Stefano Picotti, 15 Mar 2023
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RC2: 'Comment on tc-2023-19', Matthias Steiner, 11 May 2023
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The manuscript “Seismic attenuation in Antarctic firn” submitted by Picotti et al. presents a relevant study addressing the attenuation of seismic P- and S-waves in Antarctic firn. In particular, the authors develop a model based on novel combination of the Biot theory with the concept of fluidized snow filling the pore space. The results shown in the manuscript demonstrate the validity of the proposed approach and its importance for investigations of Antarctic subsurface structures and properties using seismic methods. Accordingly, the study is particularly relevant for the readership of this journal, and thus should be considered for publication after a thorough revision of the manuscript.
Main points for improvement:
- In the current version, the objective is indirectly obvious as from the current literature only sparse information regarding seismic wave velocity and attenuation in firn is available. The introduction should clearly state the objective of this study.
- Throughout the manuscript the authors use rather qualitative formulations to describe their results (e.g., “very low/high”). Considering the strong mathematical and physical background of this study such formulations should be avoided by providing a more quantitative interpretation of results or presentation of findings/values reported in the existing literature.
- The authors should be more critical about the uncertainty associated with their results especially with respect to the seismic/mechanical properties of the first (shallowest) layer.
- In the current version, the manuscript does not provide a detailed discussion of the obtained results as reflected by the manuscript structure, which does not include a Discussion section yet solely a section presenting the results.
- The conclusion is a mere summary of the main points of the manuscript, yet it does not interpret the main findings in a broader sense and does not relate them to the objectives stated in the Introduction.
Further (more detailed) comments and suggested (technical) corrections can be found in the annotated manuscript file attached here.
Stefano Picotti et al.
Stefano Picotti et al.
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