|This review is my second of this paper, and I appreciate the response that the authors gave to my first review. Many of my original questions have been well addressed in this version of the paper. I still have some concerns as well, and these (as well as areas in which my questions have been satisfied) are discussed below. |
1. I wondered if the frequencies were actually harmonic: In this draft the authors describe specific frequencies (2.5, 5, 7.5 Hz), but I still find this very difficult to see. The frequency bands shown in the spectrogram are very narrow and it’s hard to see if this is truly the frequency of the signal, or if it results from the length of the Fourier transform. Either way, I don’t see that there are clear signals at 5 or 7.5 Hz. It is also very difficult for me to see how the red/blue lines drawn on the spectrogram correspond to the actual signal…I don’t see that the lines correlate with actual frequencies in the spectrogram. Finally, the authors model upgliding and downgliding, but they do not comment on the feature that sweeps from 12 Hz to 14, and back down again. I don’t think that all signals necessarily need to be modeled, but this one stands out in all of the data but goes unnoticed or unexamined.
2. My previous review asked the authors to clarify when the landslide begins—this is now clear.
3. In my original review I expressed doubt that the slide could happen to have two asperities, both of which failed with sufficient regularity to generate identically repeating events, but one of which showed acceleration while the other showed deceleration. In this version the authors retain that model for one patch but assume the other changes by growing in size. While that is also plausible, it still feels like too great an assumption. I note that reviewer #2 in the first draft was concerned that assumptions are quickly taken to be truth, and I feel that this is a good description of this model—it still feels implausible.
4. While the authors have done a good job making the force history more clear (I appreciate the figures showing these forces), I agree with the associate editor that it’s concerning that the force history still has the landslide source at the top of the slide rather than the center of mass.
5. The authors added some important references, for which I thank them.
6. In their response to the associate editor’s comments, the authors state that the supplementary Figure 7, “shows that individual events are in fact discernable, but that they are rather jumbled in appearance and difficult to interpret”. This puzzles me, because I don’t see any discrete events within the seismogram. I’m not sure what they are referring to as individual events, but if they feels such events are existent, they should at least be pointed out. I also agree with one of the other commenters (either reviewer #2 or the associate editor) that it doesn’t make sense to have discrete events that are too small to be seen individually, yet that merge together to be recorded across the network (an argument made in the revision). It is far more compelling to consider that there never were discrete events before they were recorded as tremor.
I do think it’s reasonable to interpret tremor as being overlapping events—that’s certainly a commonly invoked mechanism. But I’m not sure there is sufficient evidence here to suggest that this is the best explanation for this particular tremor.
In summary, some things were well corrected, and I very much appreciate the care that the authors took in responding to reviewer concerns. However, I’m still unconvinced that the tremor signal comprises discrete events. I do find the signal fascinating and worthy of commentary, however.