General comments:

Distributed Acoustic Sensing (DAS) is a technique to measure strain (or strain rate) along a fiber optic cable at an unprecedented spatial resolution and is now used even in seismology. One concern of DAS is fidelity in the absolute amplitude of measured strain attributed to the coupling between the ground and the cable. In this study, based on a laborious seismic array observation at Etna volcano, the authors estimated strain by interpolating the seismic wave field with two different methods: the spatial interpolation methods and the seismo-geodetic method. Comparing these seismically estimated strain and DAS strain, the authors showed that both strains agreed well, which shows the fidelity in amplitude of DAS observation. This result made an essential contribution to validating seismological applications of DAS. And I highly evaluate the elaborate array observation by the authors in such a high mountain. The manuscript is clearly written. The subject of this manuscript is up-to-date and suitable for this journal. I would suggest this manuscript for a minor revision. The following comments should be addressed in the revised manuscript.

Specific comments (Major):

1. The two interpolation methods introduced different smoothing parameters. I am curious how these smoothing parameters are related to the gauge length of DAS. Can the authors comment on that?
2. The average inter-station distance of the seismic array observation is approximately 70m that is larger than the gauge length of 10m. Therefore, it seems reasonable that the seismically estimated strain's spatial distribution is smoother than that of the DAS strain. I wonder if the authors can increase the gauge length by taking the spatial average of DAS strain records and compare that with the seismically estimated strain. I am interested to know to what degree such a smoothing averages out the small-scale medium heterogeneities.
3. It is necessary to show the correspondence between the location and the number of DAS channels. I would suggest showing the channel number in Figure 1 with a step of 100. Or the authors will be able to indicate the channel numbers at the corners and bends of the cable in Figure 1.
4. In equation (1), the second term on the top equation's right-hand side should be w, not p. And q, p, and w may be better to be explicitly shown even in this manuscript.

Specific comments (Minor):

1. On page 5, line 113, the authors mentioned that the authors used the least-squares method to solve the system. However, since the number of data and the number of unknown parameters are the same, the authors will solve the system directly. It is not necessary to use the least-squares method.
2. In equation (5), the authors can show T (transposition operator) on the right-hand side, not on the left-hand side.
3. Page 6, line 155, fmax is about 7Hz, not 6Hz.
4. In Figure 1, the authors need to mention the red circle at Bb04. Otherwise, I misunderstand that Bb04 malfunctioned.
5. At the end of the caption of Figure 2, an average scaling factor should be 1s/km, not 1000m/s.
6. In Figures 3 and 4, the authors just mentioned that the discrepancies are large around fault zones. However, it is necessary to mention clearly if the seismically estimated strain is overestimated or underestimated.
7. I want to ask the authors to show Figures 7 and 8 on precisely the same scale as Figure 2.

General comments

I enjoyed reading this manuscript. It’s very well written and the figures are overall clear.

My only major issue concerns the general objective of the paper. In the abstract, you present your experiment as a way to understand DAS potential to detect volcano-seismic signal. You insist on the great opportunity to probe its multi-faceted activity which is again very promising. But in the end, you only analyze a volcanic explosion and a LP, and rather focus on the capability to measure strain by an in-depth comparison with the more conventional broadband deployment. This is fair and, as mentioned, interesting scientifically. Yet, I’m finding the abstract and the conclusion slightly misleading. It would be interesting to know if you have detected tremor for example? I fully understand the idea of focusing on the capability to retrieve strain measurements at volcanoes, but would modify the abstract, introduction and conclusion accordingly.

Overall, as mentioned above, I’m very positive and have only several minor comments listed below. 

Minor comments

27: suggest adding a comma: ‘Nowadays, advances’.

27-30 : suggest adding references to support these statements and guide the readers.

L.35 : what do you mean by multifaceted ?

35 : again some references are needed for Etna volcanic activity

39 : as a non-native English speaker, I’m not sure about measures. I have always used measurements instead of measures. Worth checking this in detail.

46 : ‘constraints on seismic sources’ : could you be more specific here ?

52-53 : ‘close sensors or dense arrays’ : it would be good to give some numbers here, again to guide the non-seismologists who may be interested in your contribution

58 : ‘the Authors’-> ‘the authors’

L.90 : what’s the natural frequency of the Trillium Compact

115-116 : how do you tune them ?

L.125 : odd : the size of the text suddenly increases

L.155 : it would be interesting to take a similar gauge length for the DAS to more directly compare with the broadband array

L.172 : the font size has again changed for some reason

L.183 : is that really giving a local estimate of their respective performance ? I have the feeling it somewhat highlight their discrepancy but not their performance.

L.189 : comment on Poisson’s ratio value : how did you come to this conclusion ?

L.191 : I only partly agree. RMSE misfits are also much higher in the northern and southwestern sections. Could you comment on this ? But I agree with the fault zones.

L.194-195 : this sentence is not clear to me. What is your aim ? To assess DAS performance ? Why on irregular points ?

The first paragraph is very convincing. Well done.

207 : I suggest using ‘coinciding with’ rather than ‘in correspondence’

L.220 : have you tried to compute simple H/V ratios for the broadband to better understand the site effects ?

Other questions

I would like to see a spectrum for each event before any filtering, perhaps as supplementary material.

There seems to be more phases excited following the VE compared to the LP. Could you comment on this ?

Figure 1 : strange geometry. Could you explain the rationale for selecting this geometry ? What is the DEM resolution ?

Figure 2 : I would suggest to avoid the use of jet colours for the colormap (https://gorelik.net/2020/08/17/what-is-the-biggest-problem-of-the-jet-and-rainbow-color-maps-and-why-is-it-not-as-evil-as-i-thought/).

I can’t see the red line : ‘DAS channel 501 (red line)’

Figure 4 : you should again mention here what are the open circles and black lines

Figure 6 : the green color is very hard to see

Figure 7 : any reason why there seems to be more scattering for some channels, e.g., 200 ? Any local amplification ?

Figure 8 : why are there some discrete lines around channels 600 and 300 for example ?