Vs30 Derived from Geology: An Attempt in the Province of Quebec, Canada
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors This paper compares two techniques to be used as proxy for the direct measurement of Vs30, in important parameter for seismic zonation. It is conclusive in its analysis and shows an interesting approach. The paper may be ready for publication after a major revision addressing the comments in the annotated PDF. Outside of the comments in the annotated version, it would be good for the authors to consider modifying the "Discussion" section. It contains a summary of many results and is repeating the "Results" section in many places. A new version should emphasize the assumption made, the limits of the method, the way to mitigate the limits, and the way forward.Comments for author File: 
Comments.pdf
Author Response
Thank you for your review. here are some responses to your comments. the paper has been improved thanks to the other reviewer's comments and we hope that this new version meets your general comments.
Comment 1: Amplified
Response 1: The word is corrected. Thank you.
Comment 2: The area with zonation values does not seem to have the same boundary as the black line shown on Figure 1a.
Response 2: You are right that the black line does not follow the boundary of the zonation’s area. It is more the geographical extend. The text in the legend caption is changes as followed: “The zone contoured in black line delineates the extent of the Vs30 model of Nastev et al. [42] shown in Figure 1b."
Reviewer 2 Report
Comments and Suggestions for AuthorsThis study evaluates the accuracy of Vs30 estimates derived from topographic slope against detailed zonation in Quebec, Canada, highlighting underestimations and proposing an improved approach using surface geology and sediment types for regional site class mapping. My comments are as follows:
(1) Line 54: What is the primary reason for the underestimation of Vs30 in regions affected by glaciation?
(2) Section 2.1: How does the resolution difference between the USGS-based Vs30 map and the detailed zonation map affect the accuracy of site class comparisons, especially in regions with complex geological features?
(3) Line 145: What are the commonalities and specificities in how geological and stratigraphic units influence predictive performance?
(4) Section 3.3: This study employs different statistical methods for the raster map of Saguenay and the vector map of Quebec City. What limitations might this lead to?
(5) Section 3.3: In the processing of the Saint Lawrence Valley data, the weighting was reduced to 50% based on a prior analysis showing that only 50% of the samples matched the detailed zonation categories. Could you provide more details about this analysis, such as the data used, methods, and results, to justify the rationale and necessity of this weighting adjustment?
(6) Section 3.4: For Aeolian deposits (Ed), where the low R^2 is attributed to a small sample size and the results are not shown in Figure 11, have you considered alternative approaches to supplement or validate the reliability of these findings?
Author Response
Thank you for your review. here are some responses to your comments. the paper has been improved thanks to the other reviewer's comments and we hope that this new version meets your general comments.
Comment 1: Line 54: What is the primary reason for the underestimation of Vs30 in regions affected by glaciation?
Response 1: We added the following sentences and a reference: “However, in glacial shield regions, this method may be less reliable due to the complex and heterogeneous nature of glacial deposits. Glacial regions often feature a mix of unconsolidated materials like sand, gravel, and till, as well as solid bedrock, leading to significant variations in shear-wave velocities over short distances [27]. “
- Litton, D. Vs30 Correlations for the Boston Region. Master of Science in Civil and Environmental Engineering, TUFTS UNIVERSITY, 2015, 49 pages. http://hdl.handle.net/10427/011998
Comment2: Section 2.1: How does the resolution difference between the USGS-based Vs30 map and the detailed zonation map affect the accuracy of site class comparisons, especially in regions with complex geological features?
Response 2: Two sentences are added in this section to explain, the choice of the grid resolution and how it could affect the overall discrepandcy if one would select higher resolution. The added sentences are: “This resolution corresponds to that of the data from the Saint-Lawrence Valley, which has the lowest resolution of the different regions. Considering a higher resolution could increase the discrepancy between the Vs30 data from zonation map and the USGS ones.”
Comment 3: Line 145: What are the commonalities and specificities in how geological and stratigraphic units influence predictive performance?
Response 3: As mentioned in Salsabilli et al. (2021), geological and stratigraphic units help predict how the ground responds to earthquakes by classifying soil and rock by type and layer. Geological units focus on broad patterns but may miss small vertical changes, while stratigraphic units capture the detailed layering that affects ground shaking. In simple areas, geological data is often sufficient, but in complex regions such as glaciated or river basins, stratigraphic detail improves accuracy. The best results are obtained by combining both with geotechnical data. We added the following paragraph: “As mentioned in Salsabilli et al. [40], in simple areas where the vertical changes in soil deposits are relatively smooth, geological data is often sufficient, but in regions such as glaciated or river basins with complex layering, stratigraphic details improve accuracy. The best results could be obtained by combining both with geotechnical data.”
Comment 4: Section 3.3: This study employs different statistical methods for the raster map of Saguenay and the vector map of Quebec City. What limitations might this lead to?
Response 4: The latter map is not considered in the estimate of Vs30 by geological type and the data from Quebec City is only informative. A sentence is added to express that: “This procedure applied to the Quebec City map increases the number of data points, which may reduce the accuracy of the approach if the data is used in the correlation.“
Comment 5: Section 3.3: In the processing of the Saint Lawrence Valley data, the weighting was reduced to 50% based on a prior analysis showing that only 50% of the samples matched the detailed zonation categories. Could you provide more details about this analysis, such as the data used, methods, and results, to justify the rationale and necessity of this weighting adjustment?
Response 5: This analysis has been done in a previous paper and we tried to explain that in the sentence. We re-phrase the paragraph as followed: “In the case of the Saint-Lawrence valley, this number is reduced by 50% on the basis of a previous study for the Greater Montreal Area that indicated 50% matching accuracy for a similar region using the same procedure as in section 2.1 [28]. “ We hope it is more explicitly explained.
Comment 6: Section 3.4: For Aeolian deposits (Ed), where the low R^2 is attributed to a small sample size and the results are not shown in Figure 11, have you considered alternative approaches to supplement or validate the reliability of these findings?
Response 6: To be franked, we didn’t investigate too much in this case since Aeolian deposits cover a minor part of the surface in the geological map. We added the following sentence: “The latter deposit is not investigated further as it covers a very small part of the province of Quebec and is often very shallow. “
Reviewer 3 Report
Comments and Suggestions for AuthorsDear authors, please find in attachment the paper with some suggestions.
Best regards
Comments for author File: Comments.pdf
Author Response
Thank you for your review. The responses to the comments are provided in the attached PDF. the paper has been improved thanks to the other reviewer's comments and we hope that this new version meets your general comments.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThank you for improving on the manuscript and taking into account some of my previous comments. I will point out however that no change to the Discussion section was made to take into account the one major comment I made in my previous review:
“it would be good for the authors to consider modifying the "Discussion" section. It contains a summary of many results and is repeating the "Results" section in many places. A new version should emphasize the assumption made, the limits of the method, the way to mitigate the limits, and the way forward.”
The section does not appear to have been modified at all and presents summary of the work done in the papayer and of the results. There are no discussions of the limitations of the methods and assumptions made. Once you take this major comment into account in a next revision, I believe the paper will be acceptable for publication.
Also, in the Discussion section, “In a second steps,” at the beginning of the fourth paragraph should be changed to “In a second step”.
Author Response
Comment 1: Amplified
Response 1: The word is corrected. Thank you.
Comment 2: The area with zonation values does not seem to have the same boundary as the black line shown on Figure 1a.
Response 2: You are right that the black line does not follow the boundary of the zonation’s area. It is more the geographical extend. The text in the legend caption is changes as followed: “The zone contoured in black line delineates the extent of the Vs30 model of Nastev et al. [42] shown in Figure 1b."
Comment3: “it would be good for the authors to consider modifying the "Discussion" section. It contains a summary of many results and is repeating the "Results" section in many places. A new version should emphasize the assumption made, the limits of the method, the way to mitigate the limits, and the way forward.” The section does not appear to have been modified at all and presents summary of the work done in the papayer and of the results. There are no discussions of the limitations of the methods and assumptions made. Once you take this major comment into account in a next revision, I believe the paper will be acceptable for publication. Also, in the Discussion section, “In a second steps,” at the beginning of the fourth paragraph should be changed to “In a second step”.
Response 3: Thank you for the last comment, which we did not fully address in our previous response. The discussion has been improved by adding sentences about assumptions, limitations and the need for further research. We hope that these changes meet your expectations. A version in version mode is available.
Round 3
Reviewer 1 Report
Comments and Suggestions for AuthorsThank you for taking all my comments into account. I believe the manuscript is now ready for publication.
