Peer review of: Distributed acoustic sensing of microseismic sources and wave propagation in glaciated terrain (2020)

RR2
 Reviewers' comments:
 Reviewer #1 (Remarks to the Author):
  I have re-read the (revised) manuscript. This is a solid description and early analysis of a
 pioneering data set collected in an alpine environment with a DAS/seismic system. As aptly noted
 in the paper, this technological breakthrough has numerous implications for improving knowledge
 and practical understanding of glaciological and alpine seismicity. The paper was clearly improved
 in a number of details following review. As an early exemplar of DAS data and analysis recorded
 on a glacier, I expect that this paper will be influential in accelerating already rapidly growing
 awareness and greater interest in applying this technology and its unique data acquisition
 capabilities in cryoseismology. More generally DAS systems are clearly engendering a data
 acquisition breakthrough in seismology and broader associated Earth science that I expect to be
 one of the principal advancements for the coming decade.
 
 Reviewer #2 (Remarks to the Author):
 The authors have responded to most of my questions, except on the velocity model.
 The authors still use rather high seismic velocities in the ice, and do not explain in the text how
 these values are chosen. The say that these values are "typical", but do not provide any reference.
 In the rebuttal letter, the authors explained that seismic wave velocities were adjusted to match
 both direct and reflected arrival times for the stick-slip signal.
 For locating the basal icequake, I agree with the choice of a homogeneous velocity model, since
 only direct waves are used.
 However, when modeling reflected waves, I don't think it is realistic to use a 1D model (flat ice
 layer above the bedrock). The arrival time of the reflected wave depends on the bedrock slope,
 which is 25° according to the 3D model based on radar data, but is assumed to be horizontal in
 the 1D model.
 I also don't understand why you don't use the explosions to estimate seismic wave velocities: you
 show a nice reflected wave in Figure S5B. Why can't you use it to invert for the glacier thickness
 and/or the P wave velocity?
 Of course, using a 1D model is much simpler, but it's a pity to have so nice data and
 not using a more realistic model to interpret it.
 This study is promising ... but I am a bit disappointed that this experience is not (yet) used to
 provide new information on the glacier structure or dynamics.
 
Reviewer #3 (Remarks to the Author):
 The revised version of the manuscript is an improvement with respect to the original version. The
 authors have carefully addressed all of my concerns responding to my questions and also including
 further details in the manuscript text, modifying figures and including additional figures in the
 Supplementary material. I appreciate the effort of the authors on carrying out additional analysis
 and even adding an extra note with further details on some of the more theoretical aspects of the
 system. I believe the paper is a nice proof of concept and is now of greater use to other scientists
 wanting to reproduce similar DAS experiments in glaciated regions. In my opinion, the paper is
 now publishable in its current form (except for a couple of typos).