Surface Displacements Mechanism of the Dobi Graben from ASAR Time-Series Analysis of InSAR: Implications for the Tectonic Setting in the Central Afar Depression, Ethiopia
Round 1
Reviewer 1 Report
The authors have nicely presented the work. The manuscript can be published with minor corrections. Annotated manuscript is attached herewith
Comments for author File: 
Comments.pdf
Author Response
Dear Sir / Madam,
Thank you for your instructions and the opportunity you have provided us to revise our paper on ‘Surface Displacements Mechanism of the Dobi Graben from ASAR Time-Series Analysis of InSAR, an Implication to the Tectonic Setting in the Central Afar Depression, Ethiopia.’
Your suggestions and recommendations are constructive. We are indebted and obliged to the decision reached by you for the publication of our paper.
Regarding your suggestions, we have revised, updated, and changed the spellings, phrasing patterns, and citation styles as the annotated suggestions accordingly using Microsoft Word Track change.
Finally, we thank you again for your careful reading of our manuscript and the confidence you show towards our efforts. We hope the revised manuscript will better suit the Journal of MDPI, Remote Sensing, and we thank you for your continued interest in our research.
Sincerely,
Zelalem Demissie, Ph.D.
Assistant Professor of Environmental Geoscience
Department of Geology
Wichita State University
1845 Fairmount Ave., Rm 217
Wichita, KS 67260
Reviewer Comments, Author Responses, and Manuscript Changes
Reviewer # 1
Comment: ‘The authors have nicely presented the work. The manuscript can be published with minor corrections. Annotated manuscript is attached herewith.’
Response: Thank you! We are indebted and obliged to the decision that you have reached to recommend for the paper publication.
Other comments (Annotated in the manuscript):
Title: “Of” to “of”
Heading 0: “HIGHLIGHTS”
Bullet list change order to have ENVISAT bullet first
Line 52: “[5 - 11]”
Line 53: “[4,12]”
Line 53: No need to keep redefining ACRONYMs, just use EARS
Line 53: Delete author name and year etc. Reword as, “These two categories in the AD were explained using the distribution of … mechanisms [13].”
Figure 1: fix figure as described; match arrows to the legend
Figure 1 Caption: Change as recommended. Avoid repeating ACRONYM redefinitions: EARS, AD, ECB, DEM. It is better to define ACRONYMs in the text than to introduce and define them for the first time in a figure caption. So, DEM, STRM, RSP and GAP, should have been defined in the text before the figure.
Line 68: Delete author name and year etc.
Line 69: ditto
Line 77: ECB already defined, use [1,3,15]
Line 86: What is “Afar”?
Afar is the place name in East Africa, Ethiopia. It is the northern tip of the East African Rift System and in large scale where the Nubian plate, the Arabian plate and the Somalian plate believe to meet to make a Rift-Rift-Rift Triple junctions.
Line 96: Use “30oE”
Line 104: Section is 1.1
Line 109: Use “[13,20,21]”
Line 112: Use “[15,22]”
Line 115: Use “[3,15,22]”
Line 121: Use “[18,25,26]”
Line 125: Use ”[26,29]”
Line 126: Use “[30,31]”
Line 128: Should it be “1 arc-second”
Line 129: STRM and DEM are already defined
Line 135: Delete “Jacques et al (2011)”
Line 136: Change to “It may be argued that … scale [2].”
Line 142: Use “[1,2,15,32].”
Line 146: Use “[12,17,35-37]”
Line 149: How many reports? Use the number rather than “few”
Lines 150,151: Change to “According to [38], there is …”
Line 155: Change to “[40] also illustrated…”
Line 156: Change to “40oE and 12oE”
Line 157: Change to “…strike-slip component [39].”
Line 159: Delete “by Dobure et al.”
Line 160: Should be section 1.2
Line 165: Use “[17,42]”
Lines 166,167: Use: “[4,43,44]”
Line 168: Delete “Bridges et al.”
Line 170: ditto
Line 171: delete “Bridges et al.”
Line 173: Delete “Demissie et al.”
Line 182: Delete “Dugda et al.”
Line 183: Delete “Hammond et al.”
Line 185: Delte “Reed et al.”
Line 188: Delete “Demissie et al.”
Line 194: Why is there are space in “( = 5.63 cm)” Should it be a lambda symbol for wavelength?
Line 195: ENVISAT is already defined
Line 200: LOS already defined
Line 229: Use “January 9th, 2009”
Line 252: ditto
Line 295: Delete “Reed et al. (2014)”
Line 457: LOS already defined
Line 480: Delete “crucial” and “distributed”
Lines 526,527,529: Use “110o ± 10o”
Line 533: Delete extra “Figs”
Line 534: Use “N30oE”
Line 541: Use “N110oE±10o”
Line 546: Delete: “Jacques et al.”
Line 554: Use “N110oE±10oE”
Line 558: Use “N30oE”
Response: Thank you! We found your comments extremely helpful and have revised and edited all the annotated suggestions accordingly using Microsoft Word Track change in the attached revised manuscript. We also explain about Afar. Afar is the place name in East Africa, Ethiopia. It is the northern tip of the East African Rift System and on a large scale where the Nubian plate, the Arabian plate, and the Somalian plate believe to meet to make a Rift-Rift-Rift Triple junction.
Author Response File: Author Response.pdf
Reviewer 2 Report
Review comments for “Surface Displacements Mechanism of the Dobi Graben from ASAR Time-Series Analysis OF InSAR, an Implication to the Tectonic Setting in the Central Afar Depression, Ethiopia” by Demissie and Rimmington.
Major points
- Abbreviations are often used in the manuscript. I recommend that author should not use abbreviations, except for the general words like LOS, SAR, ASAR, SBAS, GPS, ENVISAT.
- The introduction part is too complex. I recommend that the authors should rearrange the descriptions.
- Section 1.1.2 does not describe present-day crustal deformation. It is written about crustal deformation in geological time scale. Moreover, the second paragraph is written about seismological structure.
- Readers cannot refer to the document of ENVI SARscape. The authors should describe the method in general ways, not in the way depending on the software.
- Some figures need Latitude, Longitude, and scale of distance, for example, Figures 4-9.
- In Figure 8, displacements shown in (B) is not fit with (A). The displacement of Region2 should be larger than that of Region 1.
- Why are the positive and negative values reversed for (A) and (B) in Figure 9?
- For the discussion, I recommend that the author should composite both ascending and descending results and estimate quasi-EW and quasi-UD components.
Minor points
L38. “Extension is caused by normal faulting in the Dobi graben.” Isn’t this statement the opposite of cause and effect?
L42. “ENVISAT ASAR image and SBA is used to study the surface displacement.” This is not a result of this study but a well-known general fact.
L48. “Gulf of Aden Rift (GAR)” is not shown in Figure 1.
L73-74. The sentence requires citation.
L93-103. This paragraph is written about the method and result, although the introduction part.
L96. “N 30oE.” “o” should be “°.” There are many other similar descriptions.
L108-109. “mm. yr-1” should be “mm/yr.”
L195. The abbreviation “ENVISAT” is defined in the Introduction.
L416. What is “VE wrt Nub”? Please don’t use this abbreviation.
Figure 6. Please show the area of regions 1 and 2.
Figures 6 and 8. Units of the vertical axis should be “mm” because the authors said these as displacement.
Figures 7 and 9. (A) and (B) show the velocity, but (C) shows the displacement. Therefore, the unit of the displacement should be “mm.”
Figure 10. What do the colors in the figure indicate?
Author Response
March 15, 2022
Subject: Revision and resubmission of manuscript remotesensing-1631228
Dear Sir / Madam,
Thank you for your instructions and the opportunity you have provided us to revise our paper on ‘Surface Displacements Mechanism of the Dobi Graben from ASAR Time-Series Analysis of InSAR, an Implication to the Tectonic Setting in the Central Afar Depression, Ethiopia.’
Regarding your suggestions, we have revised, updated, and changed the spellings, phrasing patterns, and citation styles as the annotated suggestions accordingly using Microsoft Word Track change.
Finally, we thank you again for your careful reading of our manuscript. We hope the revised manuscript will better suit the Journal of MDPI, Remote Sensing, and we thank you for your continued interest in our research.
Sincerely,
Zelalem Demissie, Ph.D.
Assistant Professor of Environmental Geoscience
Department of Geology
Wichita State University
1845 Fairmount Ave., Rm 217
Wichita, KS 67260
Reviewer Comments, Author Responses, and Manuscript Changes
Reviewer # 2
Comment 1: Abbreviations are often used in the manuscript. I recommend that author should not use abbreviations, except for the general words like LOS, SAR, ASAR, SBAS, GPS, ENVISAT.
Response: Abbreviations are the authors’ choice, and we have followed the journal guide for authors. In addition, it saves space.
Comment 2: The introduction part is too complex. I recommend that the authors should rearrange the descriptions.
Response: We have simplified it by merging and contracting the three subsections into one. As noted, the surface displacement dynamic and the complex tectonic setting in the Afar Depression is an intricate issue that needs to be described thoroughly. Therefore, we kept essential features, while simplifying the Introduction. This allowed a reduction of 19 cited sources over the previous version, while fully describing the study area's deformation history. The number of cited sources decreased from 65 to 46. The changes have been updated using Microsoft Word Track in the attached revised manuscript as per the editor's suggestions.
Comment 3: Section 1.1.2 does not describe present-day crustal deformation. It is written about crustal deformation in geological time scale. Moreover, the second paragraph is written about seismological structure.
Response: Based on your comment #2, we have blended the main concepts of section 1.1.2 in the newly constructed introduction and deleted this section from the article.
Comment 4: Readers cannot refer to the document of ENVI SARscape. The authors should describe the method in general ways, not in the way depending on the software.
Response: We provided a citation [34] related to this comment and removed the reference Envi SARscape from the manuscript.
Comment 5: Some figures need Latitude, Longitude, and scale of distance, for example, Figures 4-9.
Response: Thank you! We found your comments extremely helpful and have revised Figures 4-9 and updated all the figures, as indicated in the attached revised manuscript and resubmitted figures.
Comment 6: In Figure 8, displacements shown in (B) is not fit with (A). The displacement of Region2 should be larger than that of region 1.
Response: We are grateful that you have brought this to our attention, which allows us to avoid any confusion our readers might have. Taking this into consideration, we made supplemental material four as found below:
Supplement 4
This section will explain the geometrical interval classification method used to provide a symbol for the displacement value detected from the ASAR data for better computer visualization.
The geometrical interval classification has several schemes, and one of them is Geometric Interval. Geometric Interval creates class breaks based on class intervals that have a geometric series. The geometric coefficient can change once (to its inverse) to optimize the class ranges. The algorithm creates geometric breaks by minimizing the sum of squares of the number of elements in each class. This ensures that each class range has approximately the same number of values and that the change between intervals is reasonably consistent.
For example, if we quickly compare the surface displacement value in mm in Figure 8B with Figure 8A, one might conclude that Figure 8B might not fit in Figure 8A. However, the latter is the velocity in mm/year, and the former is a displacement in mm, which invalidates their comparison or conclusions therefrom. The region was visualized with more than a million pixels, which makes detecting higher displacement values by visual inspection somewhat difficult. Therefore, we needed to provide additional information in the form of a graph to emphasize the interpretation. An additional advantage of charts was the provision of more information about temporal displacement variation.
B)
To aid data visualization, we divided the two regions into four new regions. Region 1 was divided into new regions 1 and 4, while region 2 was divided into new regions 2 and 3. This was described in Supplements 4A and 4B.
The subdivision indicated that the new region 4 (Unda Gamarri horst) had a larger displacement value than the other regions 1-3. (Supplement 4B, the solid red line). This was shown in Figure 5, which indicates the quality (Signal to noises ratio) of the InSAR results from descending tract-006. Particularly, the Root-Mean-Square-Error (RMSE) of Region 4 was higher. Additionally, the result from the Small Baseline Algorithm showed a significant loss of coherence in Region 4, particularly at the southeastern part of the Unda Gamarri horst (See the figure below). This was similar to what was detected in the axial part of the graben. These findings were presumably due to the changes in surface deformation resulting from frequent geodynamic processes such as strain localization and the possible presence of melt within the seismologic depth. The latter was due to the lateral oscillation of unconsolidated sediments, which frequently move and cover the central part of the graben.
Comment 7: Why are the positive and negative values reversed for (A) and (B) in Figure 9?
Response: We are also grateful that you have brought this to our attention, which gives us the opportunity to avoid any confusion our readers might have. Therefore, we provide additional supplement material five as found below:
Supplemental 5
Histograms visually summarize the Distribution of a continuous numeric variable by measuring the frequency at which the Distributed Scatter values appear in Figure 9A and 9B, as shown below. The x-axis in a histogram is a number line that has been split into number ranges or bins. For each bin, a bar is drawn where the width of the bar represents the range of the bin, and the height of the bar represents the number of data points that fall into that range. Understanding the Distribution of the InSAR data is an important step in the data exploration process.
In the first graph, we have the entire 6,527,301 distributed scatter pixels of the Descending tract-006 LOS value. Yet, in the second Distribution of velocity chart, we have only 3,699,849 distributed scatter pixels values that satisfied the criteria we set to reduce noises due to several factors that are stated in this paper. The quality indices criteria we set is to select and filter out those pixels whose temporal coherence value is less than 0.35.
Hence, in the second case, the geometrical interval classification scheme of the symbol Geometric Interval has been created for the new domain of the 3,699,849 distributed scatter pixels values. Therefore, this creates new class breaks based on class intervals that have a geometric series, presumably adjusting the color symbols based on the new population domain pixels value. As visually presented in Figures 9A and 9B which adjusted themselves through changing class colors.
We have the entire 6,527,301 distributed scatter pixels of the Descending tract-006 LOS value in the first graph. Yet, in the second Distribution of velocity chart, we have only 3,699,849 distributed scatter pixels values that satisfied the criteria that we set to reduce noises due to several factors stated in this paper. The quality indices criteria that we specify is to select and filter out those pixels whose temporal coherence value is less than 0.35.
In Figures 9A and 9B, a geometric interval was used to create class breaks based on class intervals for 6,527,301 pixels in the first case, and 3,699,849 pixels in the second case. Each distribution for pixels’ population statistics had different means and consequently different visual appearance.
Comment 8: For the discussion, I recommend that the author should composite both ascending and descending results and estimate quasi-EW and quasi-UD components.
Response: We respectfully wish to elaborate on our overall approach and why we chose not to apply the quasi-inversion model. We note that there are several approaches, which have been well developed to exploit the potential of InSAR for 3-D surface displacement determination, aside from the quasi-inversion model. For instance, some of the methods benefit from the azimuth measurements derived from the Offset-Tracking or MAI techniques but are only suitable for investigating the large sudden displacements caused by earthquakes, volcanic eruptions, or glaciers movements, for instance. In contrast, our research focused on the slow-moving surface deformation through slow, continuous stress accommodation and localization and how these stresses should distribute throughout the adjacent area. Hence we sought to apply InSAR combined with GPS data, taking advantage of their spatial and temporal complementarity. One challenge that we faced was the lack of readily available GPS measurements at the required geographical density within the Dobi graben and its surroundings. This was due to restricted deployment and operational cost limitations. Even in the case of a dense GPS network (e.g., SCIGN and GEONET), where the spatial resolution is no better than 10 km, there were no GNSS sites in our study area. Consequently, we chose not to compose a 3D rectangular dislocation model or Quasi model.
A third approach was based on the prior information about ground deformation (e.g., neglecting the N-S displacement) on-ground movement to relax the restriction on InSAR observations. Under this assumption, the N–S component was set to zero, and displacement was re-estimated based on the standardized error of U–D. Basically, by letting the N–S displacement component tend to zero, overall displacement could be decomposed into the seasonal and linear displacements in the E–W and U–D directions.
Our discussion was based on the third approach, which used prior knowledge of evidence about surface deformation for the most inhospitable area by using radar remote sensing where the available GPS data is not sufficient to develop the time series 3D inversion model. Additionally, we were able to resolve this uni-directional LOS into the actual direction of displacement by using prior information about ground deformation. The latter was made possible by combining two acquisition geometries, in our case, the ascending tract-257 and the descending tract-06 (Figs 6 and 8).
The surface movements or displacements in both geometries were determined by interpreting the same signs of LOS value from each tract as either predominantly vertical displacements, positive for uplift and negative for subsidence or movements in the east-to-west, or vice versa directions.
Since each of the 3D surface deformation approaches had its strengths and weaknesses, the most promising approach for estimating 3-D displacements from InSAR measurements should be chosen according to the features and the types of surface deformation and usability SAR and external data. We anticipate that the above argument will convince Reviewer #2 of the underlying logic and efficacy of our approach.
Minor Points:
L38. “Extension is caused by normal faulting in the Dobi graben.” Isn’t this statement the opposite of cause and effect?
Response: Thank you for this observation. Viewed through the lens of “cause and effect” our choice may appear arbitrary, but it is important to use a lens more suited to complexity with multiple, interacting processes and structures—a dense network of normal faulting.
L42. “ENVISAT ASAR image and SBA is used to study the surface displacement.” This is not a result of this study but a well-known general fact.
Response: L42 refers to the data and methods used in the research.
L48. “Gulf of Aden Rift (GAR)” is not shown in Figure 1.
Response: The solid red lines and the Dashed red lines represent the Red Sea Rift segments and the Gulf of Aden Rifts (GAR) segments.
L73-74. The sentence requires citation.
Response: Line 73-74 has been modified as “One group of scholars has debated that the RSR and the GAR spreading centers do not form a sharp, lithospheric junction; but, Acocella et al. [14], for example, arguing that both the RSR and the GAR propagate into central AD to enclose an overlap zone of ~120 km long and ~100 km wide, characterized by a dense network of cross-cutting normal faults.”
L93-103. This paragraph is written about the method and result, although the introduction part.
Response: That is true; we believe a good introduction should include what the reader will expect in the latter part of the paper. Therefore, we incorporate an outline of our methods and results.
L96. “N 30oE.” “o” should be “°.” There are many other similar descriptions.
Response: Thank you! We found your comments extremely helpful and have revised and edited all the annotated suggestions accordingly using Microsoft Word Track change in the attached revised manuscript.
L108-109. “mm. yr-1” should be “mm/yr.”
Response: Thank you! We found your comments extremely helpful and have revised and edited all the annotated suggestions accordingly using Microsoft Word Track change in the attached revised manuscript.
L195. The abbreviation “ENVISAT” is defined in the Introduction.
Response: Thank you! We found your comments extremely helpful and have revised and edited all the annotated suggestions accordingly using Microsoft Word Track change in the attached revised manuscript.
L416. What is “VE wrt Nub”? Please don’t use this abbreviation.
Response: Thank you! We found your comments extremely helpful and have revised and edited all the annotated suggestions accordingly using Microsoft Word Track change in the attached revised manuscript.
Figure 6. Please show the area of regions 1 and 2.
Response: Thank you! We found your comments extremely helpful and have revised and edited all the figures in the attached revised manuscript.
Figures 6 and 8. Units of the vertical axis should be “mm” because the authors said these as displacement.
Response: Thank you! We found your comments extremely helpful and have revised and edited all the figures in the attached revised manuscript.
Figures 7 and 9. (A) and (B) show the velocity, but (C) shows the displacement. Therefore, the unit of the displacement should be “mm.”
Response: Thank you! We found your comments extremely helpful and have revised and edited all the figures in the attached revised manuscript.
Figure 10. What do the colors in the figure indicate?
Response: The color represents the different lithological units or rocks exposed in the study area. The legend is incorporated in the updated manuscript.
Author Response File: Author Response.pdf
Reviewer 3 Report
The authors are giving a detailed study on the kinematics of the Dobi graben and the surrounding area, based on the analysis of ASAR data. The study is very detailed with a good bibliographic background. As original contribution the paper proposes a scenario for the oblique, positive LOS signals observed in different parts of the Dobi graben. In my opinion the paper is carefully written even if sometimes it goes too far with the details. I recommend its publication.
Author Response
Referee #3
March 15, 2022
Subject: Revision and resubmission of manuscript remotesensing-1631228
Dear Sir / Madam,
Your suggestions and recommendations are constructive. We are indebted and obliged to the decision reached by you for the paper publication of our paper.
We thank you again for your careful reading of our manuscript and the confidence you show towards our efforts. We hope the manuscript will better suit the Journal of MDPI, Remote Sensing, and we thank you for your continued interest in our research.
Sincerely,
Zelalem Demissie, Ph.D.
Assistant Professor of Environmental Geoscience
Department of Geology
Wichita State University
1845 Fairmount Ave., Rm 217
Wichita, KS 67260
Reviewer # 3: The authors are giving a detailed study on the kinematics of the Dobi graben and the surrounding area, based on the analysis of ASAR data. The study is very detailed with a good bibliographic background. As original contribution the paper proposes a scenario for the oblique, positive LOS signals observed in different parts of the Dobi graben. In my opinion the paper is carefully written even if sometimes it goes too far with the details. I recommend its publication.
Response: We thank you for your careful reading of our manuscript and your confidence to decide the publication of our paper.
Round 2
Reviewer 2 Report
Thank you very much for addressing some of my previous comments. I think that the manuscript was somehow improved. However, the authors did not address some of the comments, which I considered serious problems.
- The authors still describe the method in the way depending on the software. For example, in L349, the authors described, “Once more, we utilized the SARscape toolbox SBAS workflow and adjusted the following parameters for our analysis: a max normal baseline of 45% was flagged to generate a triangular connection network in the time baseline domain but, disconnected blocks were unflagged.” Flagged and unflagged are extremely software depending words. I recommend that the authors should describe the method in general ways.
- In the previous review, I commented on Figures 8 and 9. The authors replied by adding supplements 4 and 5. However, these are not answering my questions. Especially, I cannot understand why the green-colored area (negative value) in Figure 9A turned orange color (positive value) in Figure 9B by applying the method which was mentioned in supplement 5. Moreover, the orange-colored area turned yellow or green. That is, the negative and positive values are reversed. The authors mentioned it is caused by a different color scheme visual appearance, but A and B use the same color pallet. I suspect there is a serious mistake. Moreover, I think Figure 9B and Figure 8A are the same figures, but the scales of the color pallet are different in those figures. I think Figure7B and Figure 6A have the same problem.
- Because the author discussed displacement in a vertical direction, I believe it is useful to estimate quasi-components. I know that the SAR data do not have enough sensitivity to displacement in the N-S direction. Still, it can show displacement in intuitively understandable directions and support the reader’s understanding of the authors' insistence. ENVI+SARscape has a toolbox to estimate the quasi-component, that is, “Meta (or Shape) combination” in “Stacking Tools.” You can easily acquire the time-series displacement and velocity of E-W and Up-Down components.
- L41- “ENVISAT ASAR image and SBA is used to study the surface displacement.” This is not a result of this study but a well-known general fact. If you want to show the data and method used in the research, I recommend that the authors should describe “Our SBAS-InSAR analysis using ENVISAT ASAR data shows …”
Author Response
March 30, 2022
Subject: Revision and resubmission of manuscript remotesensing-1631228
Dear Sir / Madam,
Thank you for your instructions and the opportunity you have provided us to revise our paper on ‘Surface Displacements Mechanism of the Dobi Graben from ASAR Time-Series Analysis of InSAR, an Implication to the Tectonic Setting in the Central Afar Depression, Ethiopia.’
Regarding your suggestions, we have revised, updated, and changed the spellings and phrasing patterns as the annotated using Microsoft Word Track change.
Finally, we thank you again for your careful reading of our manuscript. We hope the revised manuscript will better suit the Journal of MDPI, Remote Sensing, and we thank you for your continued interest in our research.
Sincerely,
Zelalem Demissie, Ph.D.
Assistant Professor of Environmental Geoscience
Department of Geology
Wichita State University
1845 Fairmount Ave., Rm 217
Wichita, KS 67260
Reviewer Comments, Author Responses, and Manuscript Changes
Reviewer # 2
- The authors still describe the method in the way depending on the software. For example, in L349, the authors described, “Once more, we utilized the SARscape toolbox SBAS workflow and adjusted the following parameters for our analysis: a max normal baseline of 45% was flagged to generate a triangular connection network in the time baseline domain but, disconnected blocks were unflagged.” Flagged and unflagged are extremely software depending on words. I recommend that the authors should describe the method in general ways.
Response #1: Based on your comment #1, we have omitted the only Sarscape mentioned in Line 246, the SARscape is now mentioned only in the reference section, particularly at citation reference # [40]. Additionally, we are confident that the methodology of the ASAR processing is now presented in a generalized fashion, and the approach and the concepts follow the universally accepted and previously published works such as, [33-40].
- In the previous review, I commented on Figures 8 and 9. The authors replied by adding supplements 4 and 5. However, these are not answering my questions. Especially, I cannot understand why the green-colored area (negative value) in Figure 9A turned orange color (positive value) in Figure 9B by applying the method which was mentioned in supplement 5. Moreover, the orange-colored area turned yellow or green. That is, the negative and positive values are reversed. The authors mentioned it is caused by a different color scheme visual appearance, but A and B use the same color pallet. I suspect there is a serious mistake. Moreover, I think Figure 9B and Figure 8A are the same figures, but the scales of the color pallet are different in those figures. I think Figure7B and Figure 6A have the same problem.
Response #2: Thank you! We found your comments extremely helpful and have revised Figures 6A, 7B, 8A and, 9B and updated all the figures as indicated in the attached revised manuscript and resubmitted figures. We must admit that we made a genuine mistake as you already deciphered the problem in Figure 9A and 9B. In this specific case, we noticed that during the cartographic work or map designing stage for Figure 9A, we used the RMSE column or field of the process data which is found next to the mean velocity field (Column). Please check the revised and updated figures. We present here also the RMSE before and after quality control indices (the left and the right image above) as discussed in section 3.31. In addition to changing the color pallet scale for figures 6, 7, 8, and 9, we have also switched the actual mean velocity map for Figure 9A in place. We really appreciate your critical view of this work and have accordingly enhanced it qualitatively.
- Because the author discussed displacement in a vertical direction, I believe it is useful to estimate quasi-components. I know that the SAR data do not have enough sensitivity to displacement in the N-S direction. Still, it can show displacement in intuitively understandable directions and support the reader’s understanding of the authors' insistence. ENVI+SARscape has a toolbox to estimate the quasi-component, that is, “Meta (or Shape) combination” in “Stacking Tools.” You can easily acquire the time-series displacement and velocity of E-W and Up-Down components.
Response #3: Thank you again, you brought this to our attention for the second time. Our approach was to trace a lateral sense of movement in the area where most of the previous studies referred only to the presence of vertical sense of movement since they were based only the seismic focal mechanism. We emphasized that our work is about displacement along the Line Of Sight of the satellite (LOS) in both the ascending and descending orbits. From the LOS, we calculated the slope, and from that the vertical displacement and E-W horizontal displacement components. Consequently, our interpretations and discussions are based on LOS displacement for both orbital geometries. Specifically, we explicated in lines 257 to 261 how our results can be interpreted as: “Considering the different geometry of the two ASAR orbital tracts, the detected signals can be interpreted as the same signs of movement value in both geometries, showing mainly vertical movements such as positive if uplift and negative if subsidence. Likewise, opposite signs of movement value in both geometries indicate that the movement is from East to West (or vice versa).”
Moreover, there is no doubt that, using the Sarscape module we could generate a 3D displacement, but, our objective was to extract vertical and E-W horizonal components from the two different LOS geometries of ENVIronmental SATellite (ENVISAT) as per a previously published paper [34].
Finally, we appreciate the tips that you provided us on how we can generate 3D-displacement, using “Meta (or Shape) combination” in “Stacking Tools”. However, for this study, in our judgement, the Data and Methods selections were appropriate for the aims of this paper, and we followed the journal guide for authors and clarified in detail the data and methods that we followed.
- L41- “ENVISAT ASAR image and SBA is used to study the surface displacement.” This is not a result of this study but a well-known general fact. If you want to show the data and method used in the research, I recommend that the authors should describe “Our SBAS-InSAR analysis using ENVISAT ASAR data shows …”
Response #4: Thank you and we have changed this sentence “ENVISAT ASAR image and SBA is used to study the surface displacement.” To “ENVISAT ASAR image and SBA is used to study the surface displacement that shows the presence of lateral surface movements in support of Bookshelf modeling”.
Author Response File: 
Author Response.docx
