Location and Activity Changes of Slow-Moving Landslides Due to an Earthquake: Perspective from InSAR Observations

Round 1

Reviewer 1 Report

The paper aims to monitoring and assessing the location and activity changes of slow-moving landslides in a region of Japan by remote sensing techniques.

It is well structured and the data are congruent with the proposed results and discussion.

The only defect concerns the lack of a detailed geological framework of the study area, which allows to better understand the relationship described between the movements of the landslides and the geological formations involved.

I therefore suggest to insert a geological map with sufficient detail of the specific study area.

Other minor suggested changes area described below.

ABSTRACT

line 18 = change "33kmx55 km" with "33x55 km"

INTRODUCTION

line 45 = change "image has become" with "images have become"

line 58 = change "line-of-sight" with "Line-Of-Sight"

MATERIAL AND METHODS

line 93 = change "Study Aare" with "Study Area"

line 112 (Figure 1 caption) = change "....of the study area, the blue line...." with "....of the study area. The blue line...."

Insert a blank line after the caption of Figure 1

line 121 = change "single-look-complex" with "Single-Look_Complex"

line 125 = change "digital elevation model" with "Digital Elevation Model"

line 131 = insert the reference [14] after "Berardino et al."

line 142 = change "near" with "close to"

RESULTS

line 176-177 = change "...with an elevation of 200 m-500 m....." with "....with an elevation between 200 and 500 m...". Moreover, do you mean "m a.s.l."? If so, enter it.

line 238 = ??? The Modified Mercalli Intensity has not decimal value.... (see https://www.usgs.gov/programs/earthquake-hazards/modified-mercalli-intensity-scale#:~:text=The%20effect%20of%20an%20earthquake,%2C%20and%20finally%20%2D%20total%20destruction.). Moreover, the intensity classes are expressed with Roman numerals

line 361 = change the first "They" with "they"

line 380 = change "...region2...." with "...in region 2..."

REFERENCES

In general: I think you have to write the Authors with their surname (first) and with the initial of the name (after).

Moreover:

Reference [1] = Is it a part of a book? What is the book?

Reference [12] = The pages range is missing

Reference [21] = The pages range is missing

Reference [22] = what does "pp. 104502" mean?

Reference [31] = write "GEOPHY RES LETT" in lower case ("Geophys. Res. Lett."). Moreover, the pages range is missing.

Author Response

Dear reviewer，

Thank you very much for your comment sand professional advice. These opinions help to improve academic rigor of our article. Based on your suggestion and request, we have made corrected modifications on the revised manuscript. Meanwhile. the manuscript had been reviewed and edited by language services of MDPI. We hope that our work can be improved again. Furthermore, our detailed description is in the word attachment.

Yours sincerely,

Qian sun

Author Response File: Author Response.docx

Reviewer 2 Report

Overall comments: The authors have chosen to investigate an interesting topic that is appropriate for the journal Remote Sensing. I am not an expert in InSAR processing, so I cannot comment on that aspect of their work. However, I do know about landslides and focused my attention on that aspect of the paper. There are several problems that the authors will need to address before the paper will, in my opinion, be acceptable for publication. First, and most seriously, the authors write that heavy rain occurred before and/or during the earthquake but they provide no precipitation data to show the intensity, duration, and spatial variability of the rainfall. This is such a significant problem that it will essentially require a complete rewriting of the paper because that information could be important in understanding the relative contributions of rainfall and seismic shaking. Second, the authors include many statements in the results section that belong in the discussion section. They are not clearly separating their observations (results) from their interpretations. That problem could be addressed by working with a good editor. Third, I do not see any correlations between pairs of variables in Figure 12a and 12b. As I write below, the authors should calculate correlation coefficients and p-values for both pre- and post-earthquake data to demonstrate whether there are significant correlations between the variable in those graphs. Finally, the entire manuscript needs a round of editing to address both non-standard terminology (for example, scoop-like landslides) and then overall readability and understandability of the manuscript. The introduction, in particular, needs significant editorial improvement that is beyond the scope of a technical review.

Here are some specific problems that I noted as I read the paper:

line 19: "Collapsed" is the wrong word. "Failed" or, better yet, simply "moved" would be better choices.

line 34: Do the authors mean surficial process changes? I am not sure what they mean by "surface change processes".

line 35: It's inconsistent to include "small-scale soil cover destruction" as an end member of a range of "enormous landslides".

line 54: It does not make sense to me to write that slow moving landslides are "exceedingly dangerous". If anything, they are among the least dangerous of landslides because one can easily avoid them. Slow moving landslides may cause monetary or structural damage but danger implies a threat to human health or safety.

line 102: "Inject" seems like an improper word to describe infiltration of rainwater into slopes because it implies the water is forced into the slopes under pressure. It is not. It moves downward under the influence of gravity.

line 106: "Scoop-type landslides" is not a standard term. Do the authors mean rotational landslides?

line 107: The authors need to define what they mean by "retrograde fault".

line 109: The claim that "...the geological environment crease favorable circumstances for the occurrence of slow-moving landslides" is unsubstantiated. Why would not the same geological environment create favorable circumstances for fast moving landslides? The authors need to provide some basis for their claim. I do not see any justification for their claim.

line 198: Again, the authors use "collapse" in a non-standard way. Landslides generally do not involve collapse unless it is the collapse of structures built on top of them.

lines 203-205: The statement "While this is not due to the reactivation of the sediment, the strong vibration of the seismic event could also cause the shear strength of these slopes to decrease, which would cause the slope to shift" is highly speculative and without evidence. It belongs in the discussion or interpretation section, if anywhere, not in the results section.

lines 214-216: The statement "It is an intriguing phenomenon that some slow-moving landslides that existed prior to the earthquake did not exhibit activity characteristics afterward" likewise does not belong in the results section.

lines 217-218: It is not clear what the authors mean by "...we statistically compared the distribution of slow-moving landslides in terms of...Digital Elevation Model". What aspect of the digital elevation model was compared? Height of the landslide above sea level? If so, would not it be more geomorphological appropriate to use a measure such as the topographic position index rather than just the height above sea level? And, in consideration of the local bedrock geology, could height above sea level be a proxy for bedrock type? If so, that would be redundant. The authors do not provide enough information about how they used the digital elevation model separately from calculating the slope angle.

lines 222-224: "The stability of these landslides may not have accelerated after the earthquake, possibly because they are controlled by many other factors, such as lithology, landslide area, slope gravity, and soil pore water content" is a conclusion or interpretation and does not belong in the results section.

line 432: It is not clear to me that Figure 12a and 12b show any relationships between the variables plotted. The authors need to separate the before and after points into separate groups, then calculate correlation coefficients and p-values to demonstrate that the variables are related.

Author Response

Dear reviewer，

Thank you very much for your comment sand professional advice. These opinions help to improve academic rigor of our article. Based on your suggestion and request, we have made corrected modifications on the revised manuscript. Meanwhile. the manuscript had been reviewed and edited by language services of MDPI. We hope that our work can be improved again. Furthermore, our detailed description is in the word attachment.

Yours sincerely,

Qian sun

Author Response File: Author Response.docx

Reviewer 3 Report

A. InSAR detects the LOS changes , and show in mm/yr. So, the positive velocities may provide hints of surface subsidences. Some horizontal displacements also add contributions to changes of LOS. There are two possible sources of horizontal displacements: 

1. Aftershocks of the major events. It is not easy to get enough data for aftershock creeping, but some GPS permanent station data or some dislocation models can provide good informations.

2. Landslides along the slope, the direction of slopes may change the positive or negative contributions to the LOS. 

I suggest to add this point of view in the discussions. 

B. Figures 9(c), 10(c), and 11(c) are not clear. 
C. Figure 7 has 3 different colors : before, after, and both. Add one more color box for better understanding. 
D. Figure 5 is not easy to understand. Can’t see any colored velocity dots. 

Author Response

Dear reviewer，

Thank you very much for your comment sand professional advice. These opinions help to improve academic rigor of our article. Based on your suggestion and request, we have made corrected modifications on the revised manuscript. Meanwhile. the manuscript had been reviewed and edited by language services of MDPI. We hope that our work can be improved again. Furthermore, our detailed description is in the word attachment.

Yours sincerely,

Qian sun

Author Response File: Author Response.docx