the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 20 Jan 2025
High-resolution seismic reflection surveying to delineate shallow subsurface geological structures in the karst area of Shenzhen, China
Abstract. Near-surface seismic reflection surveys can produce high-resolution geological structural images for engineering and hydrological investigations. To help delineate shallow subsurface complex geological structures in a karst area and to better understand limestone cave formation, a high-resolution 2D seismic reflection profile was acquired and processed in the urban area of Shenzhen, China. The stacked images detail subsurface structures down to depths of 80–90 m, including a concave shaped reflection, two thrusts and one normal fault, as well as a hard rock basement reflection at the southern end of the profile which could not be mapped by borehole investigations due to the limited drilling depth. Our interpretations correlate well with borehole data and synthetic modeling. Limestone caves are mainly found along faults and near rivers in this area. Our results provide new insight on the formation mechanism and distribution of the karst caves. Movement along faults and erosion generated fractures and fissures in the limestone that provide channels for rainwater and groundwater to circulate. These waters, rich in carbonic acid, dissolve minerals in the limestone, resulting in the formation of underground cavities. Mapping of the subsurface with geophysical methods can contribute to mitigation of karst hazards in the Pingshan district, Shenzhen.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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CC1: 'Comment on egusphere-2024-4050', Giacomo Medici, 29 Jan 2025
General comments
Good geophysical research on karst. See below specific comments to improve your manuscript.
Specific comments
Lines 28-29. “Karst hazards pose challenges for various industries, particularly those dependent on stable ground conditions, such as construction, agriculture, and infrastructure development”. Insert recent papers that face the relationship between industry and karst environments:
- Chen, N., Valdes, D., Marlin, C., Blanchoud, H., Guerin, R., Rouelle, M. and Ribstein, P., 2019. Water, nitrate and atrazine transfer through the unsaturated zone of the Chalk aquifer in northern France. Science of the Total Environment, 652, 927-938.
- Medici, G., Munn, J.D., Parker, B.L. 2024. Delineating aquitard characteristics within a Silurian dolostone aquifer using high-density hydraulic head and fracture datasets. Hydrogeology Journal, 32(6), 1663-1691.
Line 63. Please, clearly disclose the 3 to 4 specific objectives of your research by using numbers (e.g., i, ii, and iii).
Lines 65-70. “Zhenghe-Dapu fault zone”. Is it a normal fault? Please, specify.
Lines 65-75. Please, provide more detail on the carbonate stratigraphy.
Line 220. I can see in the interpretation of the seismic line thrusts and normal faults. You need to insert in the setting more information on either compressional or extensional tectonics to back-up the output of your seismic survey.
Lines 229-238. Please, provide more detail on the nature and the geometry of the karst landforms.
Line 266. Consider inserting recent literature on karst environments that has been suggested.
Figures and tables
Figure 1. Insert symbols for the type of fault.
Figure 2a. All the tops of the wells have the same elevation. Possible? Please, check or specify that we are on a plain.
Figure 10. “Karst area”. Specify the types of karst landforms.
Figure 10. Specify the type of faults.
Citation: https://doi.org/10.5194/egusphere-2024-4050-CC1 -
AC1: 'Reply on CC1', Zhihui Wang, 26 Mar 2025
Thanks for your comments and professional suggestions. We would like to give responses point by point as following.
Specific comments and responses
Comment 1: Lines 28-29. “Karst hazards pose challenges for various industries, particularly those dependent on stable ground conditions, such as construction, agriculture, and infrastructure development”. Insert recent papers that face the relationship between industry and karst environments:
Response 1: We will add the two recent papers in the manuscript.
Comment 2: Line 63. Please, clearly disclose the 3 to 4 specific objectives of your research by using numbers (e.g., i, ii, and iii).
Response 2: The research specific objectives will be disclosed in the revised manuscript as following.
- Testing of the reflection seismic method over karst terrain.
- Comparison of reflection seismic results with geotechnical drilling.
- Integration of physical properties of samples with reflection seismic modeling.
4. Delineating shallow subsurface complex geological structures in a karst area and understanding limestone cave formation better.
Comment 3: “Zhenghe-Dapu fault zone”. Is it a normal fault? Please, specify.
Response 2: Multi-stage, complex formation of folds and faults and intensive metamorphism took place in the pre-Caledonian, Caledonian, and Hercynian to Indosinian orogenies in the southeast of China. The early activity of Zhenghe-Dapu fault zone is ductile shear, and the middle and late stages are thrust and mid-development detachment.
Comment 4: Lines 65-75. Please, provide more detail on the carbonate stratigraphy.
Response 4:
More detail on the carbonate stratigraphy including rock mass structure and lithology will be provided in the revised manuscript.
Comment 5: Line 220. I can see in the interpretation of the seismic line thrusts and normal faults. You need to insert in the setting more information on either compressional or extensional tectonics to back-up the output of your seismic survey.
Response 5: The thrusts and normal faults happened during compressional tectonics as far as we know. More information about tectonics in the region will be provided in the resubmission.
Comment 6: Lines 229-238. Please, provide more detail on the nature and the geometry of the karst landforms.
Response 6: Thanks for your suggestions. We will provide the area of the karst landform through looking for references and the geometry of karst caves from boreholes.
Comment 7: Line 266. Consider inserting recent literature on karst environments that has been suggested.
Response 7: Thanks again. We will add some recent literature on karst environments.
Figures and tables
Comment 8: Figure 1. Insert symbols for the type of fault.
Response 8: We will reproduce Figure 1 following your suggestion.
Comment 9: Figure 2a. All the tops of the wells have the same elevation. Possible? Please, check or specify that we are on a plain.
Response 9: Yes, there are on a plain. The largest elevation difference is about 0.5 m.
Comment 10: Figure 10. “Karst area”. Specify the types of karst landforms.
Response 10: Buried Karst is dominant in our research area.
Comment 11: Figure 10. Specify the type of faults.
Response 11: Good suggestion. We will specify them.
Citation: https://doi.org/10.5194/egusphere-2024-4050-AC1
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AC1: 'Reply on CC1', Zhihui Wang, 26 Mar 2025
-
RC1: 'Comment on egusphere-2024-4050', Anonymous Referee #1, 17 Feb 2025
You can find a detailed overview of my reviewer comments in the attached PDF file.
-
AC2: 'Reply on RC1', Zhihui Wang, 26 Mar 2025
Thanks for your comments and professional suggestions. Your helpful tips will help us improve our manuscript. We would like to give responses point by point as following.
Specific comments and responses
Abstract
General comment: I suggest that the authors should write a little bit more about the actual seismic results.
Page 1, lines 15-16: “The stacked images detail subsurface structures down to depths of 80-90 m, including a concave shaped reflection …”→ What are these concave shaped
reflections? Give an interpretation.
Page 1, lines 17-18: “Our interpretations correlate well with borehole data and synthetic modeling.”→ What kind of synthetic modelling?
Responses: Thanks a lot. We will give more actual seismic results in the Abstract.
- Concave shaped reflections mean seismic reflection events curved inwards in Figure 8.
- We carried out synthetic reflection seismic modelling using the 2D elastic wave equation to simulate the seismic wavefield to help us give a comparison with the actual data and used the results to help interpret geology.
Introduction
General comment: A well-written introduction.
Page 2, lines 61-62: “Our seismic results are correlated with borehole data, synthetic modeling and ground-penetrating radar data.” → What type of synthetic modelling?
Responses: We carried out reflection seismic modeling using the 2D elastic wave equation to simulate the seismic wavefield to help us give comparison to actual data and geological interpretation.
Geological setting and physical properties
Comments:
Page 3, line 65: “Shezhen” → Shenzhen
Page 3 line 72: “…and the development deep faults…”→ development of deep faults
Page 3 line 75: “gristone”→ gritstone
Page 6 line 100: “Compressional and shear velocity and density data collected in the neighborhood of study area…”→ How was the data acquired? With which method? It is only
mentioned in the table caption. Please also mention it in the text.
Page 6 line 102: “2.65 g/cm3” → Use same units in text and table. In the table you use kg/m3
Figure 1:
The colours in the small overview map in the upper left corner seem to represent other geological units than in the large figure, although the colours are similar. Please change the colours in order to prevent confusion and add the explanation to the legend.
The abbrevations Dsh, DDh, Qhal, Qhfp, C1C1 and γK1 are not explained.
In the legend, the blank spaces between words are varying in width even in the same row.
Table 1: Maybe you can also add a column with the VP/VS ratio and discuss it later. This is also an interesting geotechnical parameter.
Responses: Thanks for pointing out the spelling mistakes. We will correct them. Compressional and shear velocity were acquired by velocity logging and the density was measured by volumetric cylinder method in the lab. VP/VS ratio is an important geotechnical parameter. We will update Figure 1 and Table 1. We missed the abbreviations of Dsh, DDh, Qhal, Qhfp, C1C1 and γK1, and only presented different colours in the legend, for example, DDh with gray colour represent that medium Silurian, comprised with Feldspathic sandstone,quartz sandstone, slate, carbonaceous shale and Calcareous Sandstone.
Data acquisition and geometry
Comments:
Figure 3: In figure 3a, the names of the boreholes are barely visible. Please adjust it by
maybe changing the colour of the font.
Figure 4: The labelling of the different wave types (F, S, R, A) is poorly visible in the figure.
Maybe use a different font colour like red.
Responses: Figures 3 and 4 will be updated according to your suggestions. We will check all figures in the manuscript and make the text clear and visible.
Data processing
Comments:
Page 9, line 141: “…to remove different types of noise.” à Specify that a little bit more.
Page 9, line 144: “Post-migration were applied…” à What type of post-migration?
Responses: We applied band-pass filtering, spectral equalization and linear noise suppression were applied to remove different types of noise, including air waves, surface waves and coherence noises with low frequence. A finite difference time migration routine was used to move dipping reflectors to their true subsurface positions and collapse diffractions after stacking.
Noise attenuation
Comments:
Page 10, line 153:“…a band-pass filter with corner frequencies of 50-80-180-220 Hz was
applied…”→ Why did you choose this specific frequency range? Describe it.
Page 10, line 157:“…two sets of reflections are notable in Fig. 5c and marked with arrows.”
à The arrows are in figure 5d!
Figure 5:
In figure 5c, show also a power spectrum after spectral equalization.
In figure 5d, I can still see some remnants of the surface waves. This might impair the
quality of the stacked section.
Responses: We carried out different frequency range tests and then determined the best frequency range to be 50-80-180-220 Hz.
Arrows and a power spectrum will be added in Figure 5c.
Yes, there are still some remnants of the surface waves. Because it is difficult to eliminate surface wave completely. Stacking further filters out surface waves.
Synthetic modelling
Comments:
Figure 7: The information about VP, VS, and density for the fourth unit in figure 7a is barely
visible. Change the colour of the font.
Responses: We will change the font colour.
Results and discussion
Comments:
Page 14, line 205: “migrateed”→migrated
General comment: The description of the result is okay, but a proper discussion is missing!
You have to discuss your paper in the context of the field of research. You have to describe the meaning and relevance of your results. Furthermore, you have to compare your results with other regional studies, but, in the best case, also other studies carried out across the world. There are many other papers dealing with reflection seismic in the context of karst and also karst related to faults. Right now, you only cite and compare your results to only one paper. Besides that you should also discuss possible shortcomings of your research design, like the acquisition parameters and the processing scheme→critical analysis of the used methods.
I to separate the results and discussion chapter and to write an extra chapter only dealing the proper discussion of the results and the methods.
Responses: Thanks again. All of your professional comments and suggestions will help us improve the manuscript. We will correct the spelling mistake and improve results and discussion.
Citation: https://doi.org/10.5194/egusphere-2024-4050-AC2
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AC2: 'Reply on RC1', Zhihui Wang, 26 Mar 2025
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RC2: 'Comment on egusphere-2024-4050', Anonymous Referee #2, 20 Feb 2025
Review of "High-resolution seismic reflection surveying to delineate shallow subsurface geological structures in the karst area of Shenzhen, China"
The paper presents a high-resolution seismic reflection study conducted in Shenzhen, China, aimed at delineating shallow subsurface geological structures in a karst area. The Authors present methodologically correct, however fairly simple case study. The research is significant due to the challenges posed by karst formations to engineering and construction projects, particularly in densely populated urban areas. However, the broader significance of the findings and/or methodology beyond this specific case study remains unclear.
Comments and questions:
In the introduction Authors claim: “The seismic reflection images provide new insight in understanding the formation mechanism and distribution of karst and karst caves”, however a discussion on the broader implications of the study that would enhance its scientific contribution is lacking.
What specific new insights do you believe your study provides beyond previous research?
Can your findings be generalized to other karst regions, or are they specific to the Shenzhen geological setting and this case? Especially that the covers only a single 417-meter profile, which may not fully capture regional variations in karst structures. Have you considered extending the survey to a larger area to validate the observed structures?
Are you planning on analysing the horizontal components from measured data? What possible additional insights could that bring into your study? Consider including it in the study.
How do you plan to integrate other geophysical methods in future studies to enhance the reliability of karst detection?
Minor comments:
Figure 1: try to compress the figure. Add the location mark of the Shenzen region in a broader context.
Figure 2: are the borehole section elevations cropped to the same level? Or the elevation is so ideally constant?
Try to limit the number of references in the introduction choosing the most relevant
Citation: https://doi.org/10.5194/egusphere-2024-4050-RC2 -
AC3: 'Reply on RC2', Zhihui Wang, 26 Mar 2025
Thanks for your comments and professional suggestions. We would like to give responses point by point as following.
Comments and questions:
Comment 1: In the introduction Authors claim: “The seismic reflection images provide new insight in understanding the formation mechanism and distribution of karst and karst caves”, however a discussion on the broader implications of the study that would enhance its scientific contribution is lacking.
Response 1: We will broaden the implications of our study in the Discussion. Our responses to your comments 2-5 form a basis for us to build on.
Comment 2: What specific new insights do you believe your study provides beyond previous research?
Response 2: Previous research focused on the location of karst caves. We found that faults contributed to the formation mechanism and distribution of the karst caves. Movement along faults and erosion generated fractures and fissures in the limestone that provide channels for rainwater and groundwater to circulate. These waters, rich in carbonic acid, dissolve minerals in the limestone, resulting in the formation of underground cavities.
Comment 3: Can your findings be generalized to other karst regions, or are they specific to the Shenzhen geological setting and this case? Especially that the covers only a single 417-meter profile, which may not fully capture regional variations in karst structures. Have you considered extending the survey to a larger area to validate the observed structures?
Response 3: At present, we do not think our findings can be generalized to other karst regions, just specific to our research area. We agree with you that a 417-meter profile can not fully capture regional variations in karst structures. So we are looking for new funding to support our research and to extend the survey to a larger area to validate the observed structures in Shenzhen.
Comment 4: Are you planning on analysing the horizontal components from measured data? What possible additional insights could that bring into your study? Consider including it in the study.
Response 4: Yes, we tried to process radial and transverse components data, however, we did not get reflection from the horizontal components. Active and passive surface wave and H/V spectral ratio were also carried out.
Comment 5: How do you plan to integrate other geophysical methods in future studies to enhance the reliability of karst detection?
Response 5: We will give a comparison and evaluate different seismic exploration methods on karst detection after processing surface wave data and using the H/V spectral ratio method. Integrated passive and active seismic data analysis may give more reliable results in our research area.
Minor comments:
Comment 6: Figure 1: try to compress the figure. Add the location mark of the Shenzhen region in a broader context.
Response 6: We will update Figure 1.
Comment 7: Figure 2: are the borehole section elevations cropped to the same level? Or the elevation is so ideally constant?
Response 7: All boreholes are on a plain. The largest elevation difference is about 0.5 m. So they are nearly at the same level.
Comment 8: Try to limit the number of references in the introduction choosing the most relevant
Response 8: We will check all references carefully.
Citation: https://doi.org/10.5194/egusphere-2024-4050-AC3
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AC3: 'Reply on RC2', Zhihui Wang, 26 Mar 2025
Interactive discussion
Status: closed
-
CC1: 'Comment on egusphere-2024-4050', Giacomo Medici, 29 Jan 2025
General comments
Good geophysical research on karst. See below specific comments to improve your manuscript.
Specific comments
Lines 28-29. “Karst hazards pose challenges for various industries, particularly those dependent on stable ground conditions, such as construction, agriculture, and infrastructure development”. Insert recent papers that face the relationship between industry and karst environments:
- Chen, N., Valdes, D., Marlin, C., Blanchoud, H., Guerin, R., Rouelle, M. and Ribstein, P., 2019. Water, nitrate and atrazine transfer through the unsaturated zone of the Chalk aquifer in northern France. Science of the Total Environment, 652, 927-938.
- Medici, G., Munn, J.D., Parker, B.L. 2024. Delineating aquitard characteristics within a Silurian dolostone aquifer using high-density hydraulic head and fracture datasets. Hydrogeology Journal, 32(6), 1663-1691.
Line 63. Please, clearly disclose the 3 to 4 specific objectives of your research by using numbers (e.g., i, ii, and iii).
Lines 65-70. “Zhenghe-Dapu fault zone”. Is it a normal fault? Please, specify.
Lines 65-75. Please, provide more detail on the carbonate stratigraphy.
Line 220. I can see in the interpretation of the seismic line thrusts and normal faults. You need to insert in the setting more information on either compressional or extensional tectonics to back-up the output of your seismic survey.
Lines 229-238. Please, provide more detail on the nature and the geometry of the karst landforms.
Line 266. Consider inserting recent literature on karst environments that has been suggested.
Figures and tables
Figure 1. Insert symbols for the type of fault.
Figure 2a. All the tops of the wells have the same elevation. Possible? Please, check or specify that we are on a plain.
Figure 10. “Karst area”. Specify the types of karst landforms.
Figure 10. Specify the type of faults.
Citation: https://doi.org/10.5194/egusphere-2024-4050-CC1 -
AC1: 'Reply on CC1', Zhihui Wang, 26 Mar 2025
Thanks for your comments and professional suggestions. We would like to give responses point by point as following.
Specific comments and responses
Comment 1: Lines 28-29. “Karst hazards pose challenges for various industries, particularly those dependent on stable ground conditions, such as construction, agriculture, and infrastructure development”. Insert recent papers that face the relationship between industry and karst environments:
Response 1: We will add the two recent papers in the manuscript.
Comment 2: Line 63. Please, clearly disclose the 3 to 4 specific objectives of your research by using numbers (e.g., i, ii, and iii).
Response 2: The research specific objectives will be disclosed in the revised manuscript as following.
- Testing of the reflection seismic method over karst terrain.
- Comparison of reflection seismic results with geotechnical drilling.
- Integration of physical properties of samples with reflection seismic modeling.
4. Delineating shallow subsurface complex geological structures in a karst area and understanding limestone cave formation better.
Comment 3: “Zhenghe-Dapu fault zone”. Is it a normal fault? Please, specify.
Response 2: Multi-stage, complex formation of folds and faults and intensive metamorphism took place in the pre-Caledonian, Caledonian, and Hercynian to Indosinian orogenies in the southeast of China. The early activity of Zhenghe-Dapu fault zone is ductile shear, and the middle and late stages are thrust and mid-development detachment.
Comment 4: Lines 65-75. Please, provide more detail on the carbonate stratigraphy.
Response 4:
More detail on the carbonate stratigraphy including rock mass structure and lithology will be provided in the revised manuscript.
Comment 5: Line 220. I can see in the interpretation of the seismic line thrusts and normal faults. You need to insert in the setting more information on either compressional or extensional tectonics to back-up the output of your seismic survey.
Response 5: The thrusts and normal faults happened during compressional tectonics as far as we know. More information about tectonics in the region will be provided in the resubmission.
Comment 6: Lines 229-238. Please, provide more detail on the nature and the geometry of the karst landforms.
Response 6: Thanks for your suggestions. We will provide the area of the karst landform through looking for references and the geometry of karst caves from boreholes.
Comment 7: Line 266. Consider inserting recent literature on karst environments that has been suggested.
Response 7: Thanks again. We will add some recent literature on karst environments.
Figures and tables
Comment 8: Figure 1. Insert symbols for the type of fault.
Response 8: We will reproduce Figure 1 following your suggestion.
Comment 9: Figure 2a. All the tops of the wells have the same elevation. Possible? Please, check or specify that we are on a plain.
Response 9: Yes, there are on a plain. The largest elevation difference is about 0.5 m.
Comment 10: Figure 10. “Karst area”. Specify the types of karst landforms.
Response 10: Buried Karst is dominant in our research area.
Comment 11: Figure 10. Specify the type of faults.
Response 11: Good suggestion. We will specify them.
Citation: https://doi.org/10.5194/egusphere-2024-4050-AC1
-
AC1: 'Reply on CC1', Zhihui Wang, 26 Mar 2025
-
RC1: 'Comment on egusphere-2024-4050', Anonymous Referee #1, 17 Feb 2025
You can find a detailed overview of my reviewer comments in the attached PDF file.
-
AC2: 'Reply on RC1', Zhihui Wang, 26 Mar 2025
Thanks for your comments and professional suggestions. Your helpful tips will help us improve our manuscript. We would like to give responses point by point as following.
Specific comments and responses
Abstract
General comment: I suggest that the authors should write a little bit more about the actual seismic results.
Page 1, lines 15-16: “The stacked images detail subsurface structures down to depths of 80-90 m, including a concave shaped reflection …”→ What are these concave shaped
reflections? Give an interpretation.
Page 1, lines 17-18: “Our interpretations correlate well with borehole data and synthetic modeling.”→ What kind of synthetic modelling?
Responses: Thanks a lot. We will give more actual seismic results in the Abstract.
- Concave shaped reflections mean seismic reflection events curved inwards in Figure 8.
- We carried out synthetic reflection seismic modelling using the 2D elastic wave equation to simulate the seismic wavefield to help us give a comparison with the actual data and used the results to help interpret geology.
Introduction
General comment: A well-written introduction.
Page 2, lines 61-62: “Our seismic results are correlated with borehole data, synthetic modeling and ground-penetrating radar data.” → What type of synthetic modelling?
Responses: We carried out reflection seismic modeling using the 2D elastic wave equation to simulate the seismic wavefield to help us give comparison to actual data and geological interpretation.
Geological setting and physical properties
Comments:
Page 3, line 65: “Shezhen” → Shenzhen
Page 3 line 72: “…and the development deep faults…”→ development of deep faults
Page 3 line 75: “gristone”→ gritstone
Page 6 line 100: “Compressional and shear velocity and density data collected in the neighborhood of study area…”→ How was the data acquired? With which method? It is only
mentioned in the table caption. Please also mention it in the text.
Page 6 line 102: “2.65 g/cm3” → Use same units in text and table. In the table you use kg/m3
Figure 1:
The colours in the small overview map in the upper left corner seem to represent other geological units than in the large figure, although the colours are similar. Please change the colours in order to prevent confusion and add the explanation to the legend.
The abbrevations Dsh, DDh, Qhal, Qhfp, C1C1 and γK1 are not explained.
In the legend, the blank spaces between words are varying in width even in the same row.
Table 1: Maybe you can also add a column with the VP/VS ratio and discuss it later. This is also an interesting geotechnical parameter.
Responses: Thanks for pointing out the spelling mistakes. We will correct them. Compressional and shear velocity were acquired by velocity logging and the density was measured by volumetric cylinder method in the lab. VP/VS ratio is an important geotechnical parameter. We will update Figure 1 and Table 1. We missed the abbreviations of Dsh, DDh, Qhal, Qhfp, C1C1 and γK1, and only presented different colours in the legend, for example, DDh with gray colour represent that medium Silurian, comprised with Feldspathic sandstone,quartz sandstone, slate, carbonaceous shale and Calcareous Sandstone.
Data acquisition and geometry
Comments:
Figure 3: In figure 3a, the names of the boreholes are barely visible. Please adjust it by
maybe changing the colour of the font.
Figure 4: The labelling of the different wave types (F, S, R, A) is poorly visible in the figure.
Maybe use a different font colour like red.
Responses: Figures 3 and 4 will be updated according to your suggestions. We will check all figures in the manuscript and make the text clear and visible.
Data processing
Comments:
Page 9, line 141: “…to remove different types of noise.” à Specify that a little bit more.
Page 9, line 144: “Post-migration were applied…” à What type of post-migration?
Responses: We applied band-pass filtering, spectral equalization and linear noise suppression were applied to remove different types of noise, including air waves, surface waves and coherence noises with low frequence. A finite difference time migration routine was used to move dipping reflectors to their true subsurface positions and collapse diffractions after stacking.
Noise attenuation
Comments:
Page 10, line 153:“…a band-pass filter with corner frequencies of 50-80-180-220 Hz was
applied…”→ Why did you choose this specific frequency range? Describe it.
Page 10, line 157:“…two sets of reflections are notable in Fig. 5c and marked with arrows.”
à The arrows are in figure 5d!
Figure 5:
In figure 5c, show also a power spectrum after spectral equalization.
In figure 5d, I can still see some remnants of the surface waves. This might impair the
quality of the stacked section.
Responses: We carried out different frequency range tests and then determined the best frequency range to be 50-80-180-220 Hz.
Arrows and a power spectrum will be added in Figure 5c.
Yes, there are still some remnants of the surface waves. Because it is difficult to eliminate surface wave completely. Stacking further filters out surface waves.
Synthetic modelling
Comments:
Figure 7: The information about VP, VS, and density for the fourth unit in figure 7a is barely
visible. Change the colour of the font.
Responses: We will change the font colour.
Results and discussion
Comments:
Page 14, line 205: “migrateed”→migrated
General comment: The description of the result is okay, but a proper discussion is missing!
You have to discuss your paper in the context of the field of research. You have to describe the meaning and relevance of your results. Furthermore, you have to compare your results with other regional studies, but, in the best case, also other studies carried out across the world. There are many other papers dealing with reflection seismic in the context of karst and also karst related to faults. Right now, you only cite and compare your results to only one paper. Besides that you should also discuss possible shortcomings of your research design, like the acquisition parameters and the processing scheme→critical analysis of the used methods.
I to separate the results and discussion chapter and to write an extra chapter only dealing the proper discussion of the results and the methods.
Responses: Thanks again. All of your professional comments and suggestions will help us improve the manuscript. We will correct the spelling mistake and improve results and discussion.
Citation: https://doi.org/10.5194/egusphere-2024-4050-AC2
-
AC2: 'Reply on RC1', Zhihui Wang, 26 Mar 2025
-
RC2: 'Comment on egusphere-2024-4050', Anonymous Referee #2, 20 Feb 2025
Review of "High-resolution seismic reflection surveying to delineate shallow subsurface geological structures in the karst area of Shenzhen, China"
The paper presents a high-resolution seismic reflection study conducted in Shenzhen, China, aimed at delineating shallow subsurface geological structures in a karst area. The Authors present methodologically correct, however fairly simple case study. The research is significant due to the challenges posed by karst formations to engineering and construction projects, particularly in densely populated urban areas. However, the broader significance of the findings and/or methodology beyond this specific case study remains unclear.
Comments and questions:
In the introduction Authors claim: “The seismic reflection images provide new insight in understanding the formation mechanism and distribution of karst and karst caves”, however a discussion on the broader implications of the study that would enhance its scientific contribution is lacking.
What specific new insights do you believe your study provides beyond previous research?
Can your findings be generalized to other karst regions, or are they specific to the Shenzhen geological setting and this case? Especially that the covers only a single 417-meter profile, which may not fully capture regional variations in karst structures. Have you considered extending the survey to a larger area to validate the observed structures?
Are you planning on analysing the horizontal components from measured data? What possible additional insights could that bring into your study? Consider including it in the study.
How do you plan to integrate other geophysical methods in future studies to enhance the reliability of karst detection?
Minor comments:
Figure 1: try to compress the figure. Add the location mark of the Shenzen region in a broader context.
Figure 2: are the borehole section elevations cropped to the same level? Or the elevation is so ideally constant?
Try to limit the number of references in the introduction choosing the most relevant
Citation: https://doi.org/10.5194/egusphere-2024-4050-RC2 -
AC3: 'Reply on RC2', Zhihui Wang, 26 Mar 2025
Thanks for your comments and professional suggestions. We would like to give responses point by point as following.
Comments and questions:
Comment 1: In the introduction Authors claim: “The seismic reflection images provide new insight in understanding the formation mechanism and distribution of karst and karst caves”, however a discussion on the broader implications of the study that would enhance its scientific contribution is lacking.
Response 1: We will broaden the implications of our study in the Discussion. Our responses to your comments 2-5 form a basis for us to build on.
Comment 2: What specific new insights do you believe your study provides beyond previous research?
Response 2: Previous research focused on the location of karst caves. We found that faults contributed to the formation mechanism and distribution of the karst caves. Movement along faults and erosion generated fractures and fissures in the limestone that provide channels for rainwater and groundwater to circulate. These waters, rich in carbonic acid, dissolve minerals in the limestone, resulting in the formation of underground cavities.
Comment 3: Can your findings be generalized to other karst regions, or are they specific to the Shenzhen geological setting and this case? Especially that the covers only a single 417-meter profile, which may not fully capture regional variations in karst structures. Have you considered extending the survey to a larger area to validate the observed structures?
Response 3: At present, we do not think our findings can be generalized to other karst regions, just specific to our research area. We agree with you that a 417-meter profile can not fully capture regional variations in karst structures. So we are looking for new funding to support our research and to extend the survey to a larger area to validate the observed structures in Shenzhen.
Comment 4: Are you planning on analysing the horizontal components from measured data? What possible additional insights could that bring into your study? Consider including it in the study.
Response 4: Yes, we tried to process radial and transverse components data, however, we did not get reflection from the horizontal components. Active and passive surface wave and H/V spectral ratio were also carried out.
Comment 5: How do you plan to integrate other geophysical methods in future studies to enhance the reliability of karst detection?
Response 5: We will give a comparison and evaluate different seismic exploration methods on karst detection after processing surface wave data and using the H/V spectral ratio method. Integrated passive and active seismic data analysis may give more reliable results in our research area.
Minor comments:
Comment 6: Figure 1: try to compress the figure. Add the location mark of the Shenzhen region in a broader context.
Response 6: We will update Figure 1.
Comment 7: Figure 2: are the borehole section elevations cropped to the same level? Or the elevation is so ideally constant?
Response 7: All boreholes are on a plain. The largest elevation difference is about 0.5 m. So they are nearly at the same level.
Comment 8: Try to limit the number of references in the introduction choosing the most relevant
Response 8: We will check all references carefully.
Citation: https://doi.org/10.5194/egusphere-2024-4050-AC3
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AC3: 'Reply on RC2', Zhihui Wang, 26 Mar 2025
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Zhihui Wang
Christopher Juhlin
Qingtian Lü
Xiaoming Ruan
Zhendong Liu
Chenghua Yu
Mingchun Chen
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