Evidence of Instability in Previously-Mapped Landslides as Measured Using GPS, Optical, and SAR Data between 2007 and 2017: A Case Study in the Portuguese Bend Landslide Complex, California

Round 1

Reviewer 1 Report

This study demonstrates the capabilities of using a multi-sensor approach

for updating landslide inventories, particularly in regions experiencing a wide range of deformation (mm/year to m/year). The approach uses radar, optical and GPS measurements overcoming their drawbacks and exploiting their advantages. The authors then apply the developed methodology to the Palos-Verdes Landslide area in California.

Overall the paper is well written and fits the topic of the journal.

I have a minor comment related to the accuracy assessment of the adopted technique. I would like to see an additional figure showing a comparison with all gps (used as ground truth and showed on the X axis) VS InSAR/COSI-COrr depending on where there is signal cover.

I would be useful to list the values of the intercept and slope (+error) into a table.

Author Response

Please see the attached Word document for a point-by-point response to Reviewer 1's comments.

Author Response File: Author Response.docx

Reviewer 2 Report

There are numerous of landslide Instability paper. In general, the topic of the manuscript is a bit interesting. The authors combined several techniques for mapping landslide instability, such as GPS, Optical, and Radar Data etc. However, this paper needs revision because of hard readability and worse visibility of figures. Some extra information should be added and careful corrections should be made (suggestions are presented below).

1.         The authors combined multiple techniques and made the produced instability complicated, better to simply the framework for monitoring the deformation.

2.         Case study is too long for the length of the paper. The introduction is not enough, please deepen them using previous research.

3.         Section 4 the bold year from L214-246 and 274-299, better to make a table and compared with each other, this can help readers to easily catch the points.

4.         The quality of fig 4 is not good.

5.         Secion 5 is similar to section 4, better to make a table and compared with each other, this can help readers to easily catch the points.

6.         How to validate the accuracy of monitoring, such as data accuracy, accuracy of map, otherwise, the results is meanless.

7.         The discussion is not adequate, please explain your findings and how to contribute to the landslide field.

8.          The paper has many abbreviations terms, better to explain them in the table for the reader to catch the meaning. 

Author Response

Please see the attached Word document for a point-by-point response to Reviewer 2's comments.

Author Response File: Author Response.docx

Reviewer 3 Report

Excellent research. However, the manuscript does not have a consistent flow and may need attention of the authors. My only observation is the use word RADAR which should be replaced by SAR. I would also to suggest to add graticule to and possibly inset map to Figure 1.  Similarly, graticule may also be added to figure 2, 6 and 7.

Author Response

Please see the attached Word document for a point-by-point response to Reviewer 3's comments.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

This version is improved a lot. The first two answers are hard to follow, it is better to paste the revision in the word file and easy to catch. In the introduction, the authors mapped the instability,  thus it is better to add instability and landslide detection references, such as below:

1）  An integrated artificial neural network model for the landslide susceptibility assessment of Osado Island, Japan. Natural Hazards, 78(3), 1749–1776. doi:10.1007/s11069-015-1799-2

2）A Novel Hybrid Approach of Landslide Susceptibility Modeling Using Rotation Forest Ensemble and Different Base Classifiers. Geocarto International.
doi: 10.1080/10106049.2018.1559885

As mentioned in the first round, your new points are still unclear. The authors mixed the conclusion and discussion, please separate them. Conclusion section cited many papers, this is not correct, it should introduction or discussion. Moreover, the Conclusion should be concise.

Author Response

Please see the attached Word document for a point-by-point response to the second round of comments made by Reviewer 2. Thank you.

Author Response File: Author Response.pdf