Distribution of Active Faults and Lithospheric Discontinuities in the Himalayan-Tibetan Orogenic Zone Identified by Multiscale Gravity Analysis
Round 1
Reviewer 1 Report
Synthesis:
The authors present an interesting study about the spatial distribution of active faults and structural discontinuities in the Himalayan-Tibetan region. Using wavelet multiscale analysis of the Bouguer gravity field, they identify notable crustal discontinuities on the Pamir Plateau and within the Himalayan tectonic zone. The study reveals the prevalence of deep-crust active faults along the northern margin of Tibet and a decrease in crustal discontinuities with depth in eastern Tibet. The authors also discuss the contrasting characteristics of the western and eastern Himalayan syntaxes and the influence of the Indian plate in shaping the region's geological dynamics. These findings contribute to a deeper understanding of the tectonic processes in the Himalayan-Tibetan orogen.
Major comments:
The manuscript is well-prepared and effectively conveys clear ideas. However, the structure of the manuscript raises a concern. The authors present a significant amount of new results in the Discussion section, which should ideally be included in the Results section. Additionally, there is a lack of a comprehensive discussion that critically compares their findings with previous studies. It would greatly enhance the manuscript to include a dedicated subsection highlighting the importance and impact of this study in advancing our understanding of the Himalayan-Tibetan Orogenic Zone. I believe that the authors possess the ability to revise accordingly and better articulate their findings to our scientific community.
Specific comments
Abstract:
Overall, the abstract offers a clear and concise summary of the scientific paper, effectively capturing the main objectives, methods, and key findings of the study. However, there is room for improvement to enhance the clarity and readability of the abstract.
The sentence structure could benefit from improvements in clarity, flow, and readability. For the authors' reference, I have provided a few examples below.
Original: "To analyze the spatial distribution of major active faults and structural discontinuities in the Himalayan-Tibetan orogen, this paper presents wavelet multiscale analysis of the Bouguer gravity field."
Revised: "This paper utilizes wavelet multiscale analysis of the Bouguer gravity field to analyze the spatial distribution of major active faults and structural discontinuities in the Himalayan-Tibetan orogen."
To enhance balance and readability, it is recommended to restructure the sentence. Furthermore, it is advisable to include a preceding sentence that provides a broad introduction, highlighting the authors' perspective on the necessity and significance of the analysis.
Original: Active faults along the northern margin of Tibet are mostly visible in the deep crust, while crustal discontinuities decrease with depth in eastern Tibet.
Revised: Active faults primarily occur in the deep crust along the northern margin of Tibet, whereas crustal discontinuities gradually diminish with increasing depth in eastern Tibet.
The use of decrease in the original sentence is particularly confusing and needs clarity.
Original: "The Himalayan crust is undergoing E-W extension, and material discontinuities are significant along N-S-trending normal faults."
Revised: "The findings reveal that the Himalayan crust is undergoing east-west extension, with prominent material discontinuities observed along north-south-trending normal faults."
This revision is to partly highlight that this is a new finding in this study instead of a general statement.
The abstract could benefit from a statement about the broader implications or significance of the findings. Discussing how the research contributes to the field and why it matters can help readers understand the relevance of the study.
Introduction
This section is overall well written. One suggestion to further enhance it would be to provide a brief introduction to the techniques utilized in previous research, apart from wavelet multiscale decomposition. This would help to highlight the potential advantages and disadvantages of wavelet multiscale decomposition in comparison to other methods.
Line 75: It is currently unclear why the authors performed the 7th order decomposition, and a brief reasoning should be provided.
Figure 3: The current colormap used in this plot makes the contours difficult to read. It is recommended to select a colormap that is specifically tailored to enhance the visualization of this plot. For instance, consider changing the vast purple area to a dark gray shade to improve the background. Additionally, it is advisable to avoid using both purple and red, which are warm hues, at the low and high ends of the colormap. Currently, I notice a scarcity of colors beyond cyan in this plot, which limits the visibility of corresponding values. Furthermore, it would be beneficial to have regularly spaced labeled values on the colorbar to improve readability and interpretation.
Same issues are consistent in Figures 4-9.
Line 198: This sentence needs clarity. Do the authors mean the area with maximum THDs?
Line 269: Clarity is needed on this subsection. What will be particularly discussed here?
Figure 10: Could Figures 10-14 be relocated from the Discussion section to the Results section? The Results section should primarily present the new findings in a clear and objective manner, while subjective interpretations can be reserved for the Discussion section. By including these figures in the Results section, readers will have the opportunity to independently assess the results and form their own judgments regarding the authors' interpretations.
Line 288: It is unclear here what “it” refers to.
Line 332: Corresponds – corresponding
Figure 11. Suggest reorganizing the caption without using brackets and specify the two plots as Figure 11A and 11B. Additionally, make sure to specify the x and y axes instead of using "km" as the unit.
Figure 12: (d) are – (d) is.
The Conclusions are too long at this moment and should be condensed.
Author Response
Point 1: There is room for improvement to enhance the clarity and readability of the abstract.
Response 1: Based on the reviewer1’s suggestions, we revised the conclusion and discussion sections of the article. And based on the revision, we rewrote the abstract of the article according to the three elements: background, methods, and conclusion. In writing the abstract，we have followed the advices and the examples given by reviewer1 to make the abstract of the article more readable and help readers understand the relevance of the study. Besides, according to the reviewer1’s advise, we have explained the importance of this study and the significance and impact of our main results at the beginning of the abstract.
Point 2: The new results presented in the Discussion section should ideally be included in the Result section.
Response 2: We reviewed the discussion section in detail. We then reorganised the main findings and conclusions into four entries and elaborated them accordingly in the conclusion section. The conclusions are also be condensed. These four entries include a list of deep and large active faults cutting the lithosphere, reveal the mechanisms of three important geodynamic phenomena on the Pamir Plateau, and elucidate the coupling relationship between present-day crustal horizontal deformation characteristics and deep tectonics, as well as the role of active faults in the tectonic evolution of the region.
Point 3: The reviewer 1 suggested that we should provide a brief introduction to the techniques utilized in previous, apart from wavelet multiscale decomposition.
Response 3: We have added a paragraph (the second paragraph in revision) in the Introduction section to describe the wavelet multiscale decomposition technique and to make a brief comparison between wavelet multiscale decomposition and the techniques used in previous studies. We also explain the purpose and significance of potential field edge detection based on wavelet multiscale decomposition results.
Point4: It is currently unclear why the authors performed the 7th order decomposition.
Response 4: We have given a brief reason for this at the beginning of the corresponding paragraph. The reason is that the 7th order wavelet detail corresponds to a depth of 136 km. This depth is the maximum depth of the excess region between the crustal lithosphere and the upper mantle in the study area.
Point 5: The current colormap used in this plot makes the contours difficult to read. It is recommended to select a colormap that is specifically tailored to enhance the visualization of this plot. For instance, consider changing the vast purple area to a dark gray shade to improve the background. Additionally, it is advisable to avoid using both purple and red, which are warm hues, at the low and high ends of the colormap. Currently, I notice a scarcity of colors beyond cyan in this plot, which limits the visibility of corresponding values. Furthermore, it would be beneficial to have regularly spaced labeled values on the colorbar to improve readability and interpretation. Same issues are consistent in Figures 4-9.
Response 5: Based on reviewer1's suggestion, we have reprogrammed the cpt files used by the GMT software by replacing the background color of Figures 3 to 9 with light grey. We have also increased the range of values corresponding to yellow and red. The areas covered by the warm colors only correspond to very high values. To further improve the readability of the figures, we have also increased the font size of the characters.
Point 7: Some sentences are not clarity.
Response 7: We have made appropriate corrections to the sentences where the reviewer pointed out a lack of clarity.
Point 8: Suggest reorganizing the caption without using brackets and specify the two plots as Figure 11A and 11B. Additionally, make sure to specify the x and y axes instead of using "km" as the unit.
Response 8: We have add the label (a) and (b) in figure11. And the unit of x and y axes in Figure 11(b) is km.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Review: applsci-2487055
Distribution of active faults and lithospheric discontinuities in the Himalayan-Tibetan Orogenic zone identified by multiscale gravity analysis
Wu Xiaolong, Wu Jifeng, Xiang Yang, Khan Muhammad Sohail
General comments
This submission has applied wavelet multiscale analysis of the Bouguer gravity field and the total horizontal derivative (THD) at various depths to reveal a detailed spatial distibution of active fault and lithospheric discontinuities in the Himalayan-Tibetan Orogenic zone, an area that is well known for its crustal deformation within the India-Eurasia collision system. The submission has the potential to be a useful contribution and should, in my view, eventually be published. Prior to that point it needs some attention in various places. The main text is well presented with moderate corrections in English language. The Font size of the labels in all the maps should be increased to allow for easy reading. Check the references and make sure they conform with the style of applied sciences. The instructions to author for the Journal should be followed before preparing and submitting the manuscript.
Specific comments
Abstract: The opening sentence should invite the reader. What is new??
Bouguer gravity anomalies:Avoid starting sentences with As shown in Figure 2 or Figure 2h show. Example line 135 can be rephrased thus.. the wavelet approximation of the entire study area, which relates to the material distribution in the deep earth is presented in Figure 2. Same hold for in Figure 3, in Figure 4, in Figure 6, in Figure 7....check and rephrase the sentences. To avoid repeatition in the text weedout interpretation an discussion from the results and present them in the discussion section. Example lines 109-112, line 165-166
Line 79 abbreviations should be written first of all in full example, vertical derivative (VDR)..and not VDR (vertical derivative) this applies to all the abbreviations in the text
Line 166 introduce a space between above and mentioned
Line 172 omit the t in structural
Line 178 are much smaller than those...omit the
Line 178. It is clear that what you are presenting is according to your calculations so avoiding using such. Same holds for lines 183, 230 and 280
Line 495 should be rephrased
Figures...:
It is important that the font size of the labels in all the maps be increased. It is not clear at the present state.
In general, this is an interesting piece of research and in my view should be publised after the corrections are effected.
Comments for author File: Comments.pdf
English needs moderate editing
Author Response
Point 1 : The Font size of the labels in all the maps should be increased to allow for easy reading.
Response 1: We have doubled the size of the font in the figures.
Point 2: The opening sentence should invite the reader. What is new??
Response 2: We reviewed the discussion section in detail. We then reorganised the main findings and conclusions into four entries and elaborated them accordingly in the Abstract. These four entries include a list of deep and large active faults cutting the lithosphere, reveal the mechanisms of 2 important geodynamic phenomena on the Pamir Plateau, and elucidate the coupling relationship between present-day crustal horizontal deformation characteristics and deep tectonics, as well as the role of active faults in the tectonic evolution of the region.
Point 3: Avoid starting sentences with As shown in Figure 2 or Figure 2h show. Example line 135 can be rephrased thus.. the wavelet approximation of the entire study area, which relates to the material distribution in the deep earth is presented in Figure 2. Same hold for in Figure 3, in Figure 4, in Figure 6, in Figure 7....check and rephrase the sentences. To avoid repeatition in the text weedout interpretation an discussion from the results and present them in the discussion section. Example lines 109-112, line 165-166
Response 3: We have carefully read the whole paper and rephrased all the problems in the description of the figures and those pointed out by reviewer 2. We have also removed duplication of discussion in the main text.
Point 4: Abbreviations should be written first of all in full example, vertical derivative (VDR)..and not VDR (vertical derivative) this applies to all the abbreviations in the text.
Response 4: We have revised all abbreviations, including all fault’s names, as suggested by the reviewer 2. Throughout, abbreviations are given where they first appear, and only abbreviations are used where they reappear later. Full names are used in the abstract.
Author Response File: Author Response.pdf
Reviewer 3 Report
The article is well written overall. However, too many shapes are used. Also, the fonts are very small and difficult to read. However, abbreviations should be given in the figure captions and some missing references should be added. If possible, a geological map showing the main tectonic units should be attached along with the tectonic lines. So the article will be more understandable and useful.
Comments for author File: Comments.pdf
Author Response
Points 1: The fonts are very small and difficult to read. However, abbreviations should be given in the figure captions and some missing references should be added. If possible, a geological map showing the main tectonic units should be attached along with the tectonic lines. So the article will be more understandable and useful.
Response 1: As suggested, we have included the full names and abbreviations of the main structures in the study area under the title of Figure 1 in this paper. The font size in the paper diagram has been increased.
Author Response File: Author Response.pdf
