Balancing Submarine Landslides and the Marine Economy for Sustainable Development: A Review and Future Prospects

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript gives a general review about marine geologic hazards, and its impacts on marine environment and economy. It might be valuable and intertesting for the marine resources planning and development community. The manuscript is well organized, and the writing is fine for me. I would like to recommend accepting the manuscript after the following minor revisions:

(1) The meaning and logic of Section 4 should be clarified, especially section 4.1. Since you are focusing on marine disaster at a large scale or policy level, and seldom talk about the technical study of submarine landslides;

(2) Section 6 should be section 5.

Comments on the Quality of English Language

The writing quality is fine for me. 

Author Response

Authors’ responses to the comments of Reviewer #1:

 

1, The meaning and logic of Section 4 should be clarified, especially section 4.1. Since you are focusing on marine disaster at a large scale or policy level, and seldom talk about the technical study of submarine landslides;

>Response: Thank you for your valuable advice. We have clarified the meaning and logic of Section 4, especially Section 4.1.

>Implemented: The meaning and logic of the clarified Section 4 are shown in Lines 428-448. Due to the significant impact of submarine landslides on the advancement of deep-sea energy security and the prevention and control of marine geological disasters, research in this field has experienced rapid promotion [151]. At present, the research is focused on three key areas: trigger formation mechanisms, motion evolution processes, as well as impacts on submarine infrastructure [120]. Herein the mechanisms of trigger formation and the processes of motion evolution have been introduced and analyzed in Sections 2 and 3. Accordingly, this section mainly discusses the influence of submarine landslide technology on submarine infrastructure. Traditional techniques such as marine geological investigations, numerical simulations, and laboratory simulation tests have become the foundation of research [132,152]. With advancements in research, the close integration of advanced techniques and conventional methods has become a necessary requirement for accurately investigating submarine landslides (Figure 8). In recent years, the research of domestic and foreign scholars has mainly focused on the impact of sub-marine landslides on submarine cable systems, including oil and natural gas pipelines, submarine optical cables, and other types of cables. Nevertheless, submarine pipelines, which serve as crucial "lifelines" for marine power transmission and oil and natural gas development, are prone to being severed by submarine landslides, thus impacting the smooth progress of subsea exploitation such as oil, natural gas, and metal ores [153-155]. Hence, subsequently, we will analyze the numerical simulation of the submarine pipeline, the physical experiment simulation, and the research progress of other deep-sea facilities. The meaning and logic of the clarified Section 4.1 are shown in Lines 451-483. Numerical simulation technology has the advantages of precision and controllability for predicting and calculating the degree of damage caused by submarine landslide disasters, and it can even provide technical means to prevent large-scale MGHs. In particular, the application of numerical computing technology to simulate the impact of submarine landslides on pipelines is not limited by space, and it can capture all the variable information within the calculation domain. Currently, the commonly employed numerical methods for simulating submarine landslide-induced pipeline impacts include the finite element method (FEM), particle finite element method (PFEM), computational fluid dynamics method (CFD), and material point method (MPM). In FEM simulations of pipeline impacts caused by landslides, the impact force on pipelines is typically considered as a uniform load. The safety of pipelines under landslide impact is evaluated by taking into account various factors such as different impact loads and widths, properties of sliding bodies, and pipeline materials [156,157]. PFEM method is a novel approach for simulating the impact of submarine landslides on pipelines, develop- ed as an extension of FEM to address the challenge of modeling large deformations in rock and soil masses. Zhang et al. employed the PFEM method to simulate the entire process of slope instability and its impact on pipelines, providing a comprehensive understanding of the phenomenon [158]. CFD method is a conventional approach for simulating the impact of submarine landslides on pipelines, with a primary focus on resolving the impact behavior of submarine landslides on pipelines during the flow-slippage stage (Figure 9). Numerous scholars have utilized the CFD method to simulate the effects of submarine landslides on pipelines, considering various complex factors such as initial velocity, slide thickness, and pipeline burial depth. As a result, they have enriched and advanced the prediction model for pipeline stress under landslide impact [159]. Based on this basis, Fan et al. and Guo et al. utilized the CFD method to optimize the design of submarine pipelines and proposed a pipeline optimization scheme that effectively reduces the impact of landslides, providing assistance for the safe transmission of deep-sea energy [154,160]. Unlike the aforementioned three methods, the MPM method is a meshless approach that offers significant advantages in simulating problems involving free surfaces. Dong et al. used this method to simulate the pipe-soil interaction during the initial stage of landslide movement and subsequently refined the formula for evaluating pipeline impact by integrating principles of soil mechanics and fluid dynamics [161].

 

2, Section 6 should be section 5.

>Response: Thank you for your valuable advice. We have changed Section 6 to Section 5.

>Implemented: As shown in Line 548. 5. Conclusions and prospects.

 

3, The writing quality is fine for me.

>Response: Thank you for your valuable advice. The writing quality in the manuscript has been slightly improved due to the need for minor polishing of English grammar and writing suggested by other reviewers.

>Implemented: As indicated by the red font in the text of the manuscript.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The article is a wide-ranging review of the origins of submarine landslides and the associated risks, particularly the economic risks. Given the broad scope of the work, the article appears sometimes very general and even a little superficial, which means that certain conclusions need to be moderated. For example, in point 2 of the conclusion, lines 563 to 568 seem to me to go too far and mention results that are not supported by the facts presented. I suggest removing these lines or revising these sentences.

Author Response

Authors’ responses to the comments of Reviewer #2:

 

1, The article is a wide-ranging review of the origins of submarine landslides and the associated risks, particularly the economic risks. Given the broad scope of the work, the article appears sometimes very general and even a little superficial, which means that certain conclusions need to be moderated. For example, in point 2 of the conclusion, lines 563 to 568 seem to me to go too far and mention results that are not supported by the facts presented. I suggest removing these lines or revising these sentences.

>Response: Thank you for your valuable advice. Firstly, we have conducted a comprehensive review of the manuscript's text and enhanced certain general terms. Additionally, we have removed lines 563 to 568 for point 2 in the conclusion.

>Implemented: Revise the more general discourse from Lines 116-118, “Thus, it is imperative to conduct a comprehensive review and forward-looking analysis of the causes, effects, and remedies for submarine landslide disasters in order to achieve sustainable development of marine environment and economy.” to Lines 114-116, "Therefore, it is imperative to conduct a comprehensive review and forward-looking analysis of the causes, effects, and remedies for submarine landslide disasters.". Delete the sentence "Therefore, research in this area will continue to deepen." in Line 514. Delete the sentences in Lines 563-568 as shown in Section 5.

5. Conclusions and prospects

MGH, particularly submarine landslides, have the potential to trigger tsunamis and cause coastal erosion, posing hidden threats to the sustainable development of marine ecosystems and economies. Herein a comprehensive review of the temporal and spatial distribution, classification, character- istics, as well as inductions of submarine landslides. Moreover, it analyzes the safety hazards, environmental pollution, and economic losses that submarine landslides pose to the deep-sea mining industry. Finally, this research summarizes the technical applications and future development directions of submarine landslides. The main conclusions and prospects are as follows:

(1) Submarine landslide hotspots are predominantly concentrated in the Pacific, Atlantic, and Indian Oceans, with notable occurrences in northern Brazil and eastern Venezuela as well as the eastern, western, and southern regions of the United States. The classification criteria for submarine landslides vary. The narrow definition refers to the process of weakly structured rock sliding rapidly along a slope under the influence of gravity, including translational and rotational landslides. Moreover, the broader concept encompasses various sediment transport processes, such as creep, collapse, and gravity flow.

(2) The primary triggering factors of submarine landslides are earthquake and active fault activity (26.82%), rapid deposition (15.61%), and gas hydrate decomposition (7.39%). In deep-sea environ- ments below 1000 m, seismic and active fault activity as well as natural gas hydrate decomposition are considered the two main causes. Moreover, the typical characteristics of submarine landslides typically comprise the head stretch region, body slip region and toe extrusion region.

(3) Based on investigations and predictions of the C-C area of the international seabed, it is believed that China and Mexico are currently the only production bases in the world capable of carrying out large-scale smelting and processing of deep-sea mineral resources, with promising prospects for development. Additionally, we contend that deep-sea mining offers superior economic and environ- mental advantages compared to land-based mining.

(4) The investigation of submarine geological hazards is of great significance to the formulation and implementation of China's marine strategy. Currently, numerical simulation and physical model testing are the primary research methods for submarine landslides. In general, the workflow of ocean engineering necessitates the investigation and assessment of geological hazards, as well as the establishment of risk plans prior to implementation. With the rapid development of China's ocean industry, it is crucial to enhance techniques for identifying and analyzing deep-water landslide disasters, conducting in-situ monitoring, and performing numerical simulations, particularly with regard to deep-sea seabed in-situ monitoring. In the future, we aim to achieve sustainable develop- ment of the marine environment and economy by establishing a multi-level and multi-dimensional monitoring chain that takes into account ecological, environmental and economic factors.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Many thanks for giving me the opportunity to review the manuscript of Zuer Li and Qihang Li. titled “Balancing Submarine Landslide and Marine Economy for Sus-2 tainable Development: A Review and Prospects”. The research topic is suitable for the journal, and it appears that the research place is very interesting. However, the manuscript needs major revisions before it can be considered for publication in the journal. The main reasons for this decision are as follows.

 

1. The abstract gives a sound overview of the research objectives, methodology, and results. Nonetheless, it could be improved with a more succinct presentation of the core findings. It is advisable to refine the abstract to emphasize the research's novel contributions and its broader implications.

 

2. The introduction appropriately sets the stage for the research, but it could be improved with a succinct summary of the current state of research to better articulate the significance of the paper. Additionally, the introduction fails to identify the valuable and significant questions that remain unresolved or controversial in prior research. It also does not outline the methods that will be used to address these scientifically meaningful issues. A critical aspect that needs to be addressed is whether the research duplicates existing work or offers new discoveries, innovative solutions, and some practical or theoretical value.

 

3. In the theoretical introduction section, emphasize the most recent and pertinent research to reinforce the foundation of the paper. Ensure that the literature review is exhaustive, covering pivotal studies and theories to prevent misleading interpretations due to bias. Simultaneously, highlight significant gaps in prior research that are crucial and carry substantial significance.

 

4. In the discussion section, the research findings are meticulously connected to the broader implications for ocean policy and sustainable development. This section should delve deeply into the significance of the results, comparing them with prior research and discourse. It should also consider the potential ramifications for practical applications and policy-making. Furthermore, the discussion should address any inherent limitations of the study and examine how these constraints might influence the validity and interpretation of the conclusions。

 

5. The conclusion should succinctly summarize the study's key findings and suggest potential directions for future research. In this section, the conclusion summarizes the core aspects and significance of the research findings in concise terms, and, based on the results, offers recommendations for future research directions or policy adjustments. The content of the response should be precise and moderate in length, avoiding being too brief to omitted important information and not too long to be redundant.

 

6. To enhance the professionalism and readability of the article, professional language editing is essential. Engaging native English speakers or professional editors can ensure a comprehensive text review.

 

7. Ensure that all technical information and data presented in the text are precise and accurate, steering clear of any potential to mislead the reader. It is crucial to clearly articulate the original contributions of the article and to explain how these contributions advance the field by building on or expanding existing research.

Comments on the Quality of English Language

Minor editing of English language required

Author Response

Authors’ responses to the comments of Reviewer #3:

 

1, The abstract gives a sound overview of the research objectives, methodology, and results. Nonetheless, it could be improved with a more succinct presentation of the core findings. It is advisable to refine the abstract to emphasize the research's novel contributions and its broader implications.

>Response: Thank you for your valuable advice. We have refined the abstract to emphasize novel contributions and their broader implications.

>Implemented: As shown in Lines 9-29. To proactively respond to the national 14th Five-Year Plan policy, we will adhere to a comprehensive land and sea planning approach, working together to promote marine ecological protection, optimize geological space, and integrate the marine economy. This paper provides a comprehensive review of sustainable development in marine geological hazards (MGHs), with a particular focus on submarine landslides, the marine environment, as well as the marine economy. Firstly, the novelty of this study lies in reviewing and summarizing the temporal and spatial distribution, systematic classification, inducible factors, and realistic characteristics of submarine landslides to enrich the theoretical concept. Moreover, the costs, risks, and impacts on the marine environment and economy of submarine engineering activities such as oil and gas fields as well as metal ores were systematically discussed. Combined with the current marine policy, an analysis was conducted on the environmental pollution and economic losses caused by submarine landslides. Herein the key finding is that China and Mexico are viable candidates for future large-scale offshore exploitation of oil, gas, nickel, cobalt, cuprum, manganese, and other mineral resources. Compared to land-based mining, deep-sea mining offers superior economic and environmental advantages. Finally, it is suggested that physical model tests and numerical simulation techniques are effective means for investigating the triggering mechanism of submarine landslides, their evolutionary movement process, and the impact on submarine infrastructure. In the future, the establishment of a multi-level and multi-dimensional monitoring chain for submarine landslide disasters, as well as joint risk assessment, prediction, and early warning systems, can effectively mitigate the occurrence of submarine landslide disasters and promote sustainable development of marine environment and economy.

 

2, The introduction appropriately sets the stage for the research, but it could be improved with a succinct summary of the current state of research to better articulate the significance of the paper. Additionally, the introduction fails to identify the valuable and significant questions that remain unresolved or controversial in prior research. It also does not outline the methods that will be used to address these scientifically meaningful issues. A critical aspect that needs to be addressed is whether the research duplicates existing work or offers new discoveries, innovative solutions, and some practical or theoretical value.

>Response: Thank you for your valuable advice. We have improved the introduction according to the reviewer's comments. Firstly, we have made a succinct summary of the current state of research to better articulate the significance of the paper. Secondly, we have shed light on valuable questions from previous research that remain unresolved or controversial. Moreover, We have outlined the methods that will be used to solve these scientifically relevant problems. Finally, we have presented the new findings of this research, as well as some practical and theoretical value.

>Implemented: 

Firstly, we present the comprehensive structural framework of the abstract section.

The first paragraph introduces the general background of the study on marine geological hazards, including the detrimental effects of these disasters and China's planning for and implementation of marine strategic policies.

The second paragraph further analyzes the casualties and property losses caused by marine geological hazards in China, introduces the types, formation characteristics, and degree of harm associated with these hazards while emphasizing the importance of investigating them.

The third paragraph emphasizes that submarine landslides are an important form of marine geological hazards and highlights the harm they cause to the marine environment and economy through practical cases, stressing the necessity of conducting comprehensive reviews and prospective analyses on the causes, effects, and prevention measures of submarine landslide hazards.

The fourth paragraph introduces the current research status, research methods, research findings, and limitations.

The fifth paragraph highlights how this study distinguishes itself from previous studies, emphasizes its innovation, and addresses the problems it solves.

Based on the reviewer's comments, the revised content in the manuscript is as follows:

A concise summary of the current research status can be found in Lines 130-142. At present, the primary research methods for deep-sea landslides are focused on geological surveys, physical exploration, laboratory testing, numerical simulations, in-situ long-term observations and monitor- ing, as well as early warning technologies [53,54]. In China, the study of geological hazards caused by deep-sea landslides began in the 1980s [55]. Since then, significant breakthroughs has been achieved in identifying, classifying, determining influencing factors, as well as monitoring-warning submarine landslide elements (Table 1). Nevertheless, these studies in Table 1 still have some short- comings, as well as no systematic analysis has been conducted on the formation mechanism, type, distribution characteristics, scale, and scope of submarine landslides. Moreover, over the past decade, research on submarine landslides in China has primarily focused on laboratory tests and numerical simulations, with few studies conducted on the environmental degradation and economic evaluation resulting from submarine landslides.

Unsolved or controversial problems in previous studies such as Lines 137-142. Nevertheless, these studies in Table 1 still have some shortcomings, as well as no systematic analysis has been conducted on the formation mechanism, type, distribution characteristics, scale, and scope of submarine land- slides. Moreover, over the past decade, research on submarine landslides in China has primarily focused on laboratory tests and numerical simulations, with few studies conducted on the environ- mental degradation and economic evaluation resulting from submarine landslides.

The measures and methods used to address these scientific problems are outlined in Lines 143-149. Accordingly, to prevent submarine landslide disasters and achieve sustainable development of the marine environment and economy, it is necessary to take appropriate measures. Herein, 1) the distribution, classification, triggering mechanisms and characteristics of submarine landslides are thoroughly discussed; 2) the environmental pollution and economic losses caused by submarine landslides are systematically analyzed; and 3) the current theories and technologies applied to submarine landslides are comprehensively introduced.

The new findings of this research are presented, along with some practical theoretical values such as Lines 149-155. In this study, the key finding is that China and Mexico are viable candidates for future large-scale offshore exploitation of oil, gas, nickel, cobalt, cuprum, manganese, and other mineral resources. Compared to land-based mining, deep-sea mining offers superior economic and environ- mental advantages. In addition, it provides a comprehensive answer on how to achieve sustainable development among submarine landslide disasters, marine environments and economies while also prospecting for the future based on current trends.

 

3, In the theoretical introduction section, emphasize the most recent and pertinent research to reinforce the foundation of the paper. Ensure that the literature review is exhaustive, covering pivotal studies and theories to prevent misleading interpretations due to bias. Simultaneously, highlight significant gaps in prior research that are crucial and carry substantial significance.

>Response: Thank you for your valuable advice. In the theoretical introduction section, firstly, we have emphasized the most recent and pertinent research to reinforce the foundation of the paper. Moreover, we have conducted a thorough examination of the manuscripts to ensure that the literature review is exhaustive and covers pivotal studies and theories. Finally, we have highlighted significant gaps in prior research that are crucial and carry substantial significance.

>Implemented: In the theoretical introduction section, emphasis is placed on the most recent and pertinent research such as Lines 201-213. Since 2013, although some scholars still maintain that submarine landslides and sediment gravity flows are distinct phenomena [93], the prevailing view has shifted towards a more generalized concept of submarine landslides [70,94,95]. On the contrary, with regards to the classification of submarine landslide calculation, Feng et al. categorized submarine landslide types based on factors such as the volume and thickness of the landslide, as well as the relationship between strata and sliding surface [96]. This classification is presented in Table 2. Overall, the narrow definition of submarine landslides refers to the rapid sliding process of unconsolidated soft sediment or rock with weak structural planes along a slope under the influence of gravity. This includes both translational and rotational landslides. The broad concept of submarine landslides encompasses various sediment transport processes, including creep, collapse, and gravity flow (such as clastic flow, particle flow, liquefaction flow, and turbidity currents). For example, the most recent and pertinent references as shown in Lines 780-785. Sassa, S.; Takagawa, T. Liquefied gravity flow-induced tsunami: first evidence and comparison from the 2018 Indonesia Sulawesi earthquake and tsunami disasters. Landslides 2019, 16, 195-200; Wang, W. W.; Wang, D. W.; Wu, S. G.; Volker, D.; Zeng, H. L.; Cai, G. Q.; Li, Q. P. Submarine landslides on the north continental slope of the South China Sea. J. Ocean U. China 2018, 17, 83-100; Wang, F. T.; Zhao, B.; Li, G. Prevention of Potential Hazards Associated with Marine Gas Hydrate Exploitation: A Review. Energies 2018, 11, 2384.

Moreover, in the theoretical introduction section, emphasis is placed on the most recent and pertinent research such as Lines 256-269. This can lead to volumetric expansion of the low-permeability layer, resulting in inadequate discharge of excess water and natural gas, thereby promoting the formation of overpressured fluid. However, the reduction of effective stress in marine sediments caused by overpressure can trigger submarine landslides. Previous studies have suggested that the decomposition of gas hydrates may be linked to other triggers. For instance, global warming or alterations in ocean current patterns can result in an increase in temperatures on the seabed, which subsequently triggers gas hydrate decomposition. Furthermore, the methane generated from decomposition exacerbates the phenomenon of global warming, triggering a chain reaction that leads to more frequent undersea landslides [107]. A significant number of submarine landslides have been identified in the Pearl River Estuary Basin of the South China Sea since the 1990s [108,109]. Despite the remarkable progress made in investigating seabed surface stability within the hydrate test area of the South China Sea, further research is needed to fully understand the mechanism behind seabed instability [110-112]. For example, the most recent and pertinent references as shown in Lines 812-817. Ren, Z. Y.; Zhao, X.; Liu, H. Numerical study of the landslide tsunami in the South China Sea using Herschel-Bulkley rheological theory. Phys. Fluids 2019, 31, 056601; Chen, D. X.; Zhang, G. X.; Dong, D. D.; Zhao, M. X.; Wang, X. J. Widespread Fluid Seepage Related to Buried Submarine Landslide Deposits in the Northwestern South China Sea. Geophys. Res. Lett. 2022, 49, 1-10; Zhu, Y. H.; Wang, P. K.; Pang, S. J.; Zhang, S.; Xiao, R. A Review of the Resource and Test Production of Natural Gas Hydrates in China. Energy Fuels 2021, 35, 9137-9150.

Check and make sure the literature review is exhaustive and covers the key research and theory as shown in the “References” section. For example, in terms of the theoretical introduction to typical characteristics of submarine landslides, White and Mckenzie conducted studies in [113], Abu et al. in [114], and Fu et al. in [115] respectively. As shown in Lines 822-828. White, N.; Mckenzie, D. Formation of the "steer's head" geometry of sedimentary basins by differential stretching of the crust and mantle. Geology 1988, 16, 250-253; Abu, C.; Jackson, C. A. L.; Francis, M. Strike-slip overprinting of initial co-axial shortening within the toe region of a submarine landslide and a model for basal shear surface growth: a case study from the Angoche Basin, offshore Mozambique. J. Geol. Soc. London 2022, 179, jgs2021-032; Fu, C.; Yu, X. H.; Fan, X.; He, Y. L.; Liang, J. Q.; Li, S. L. Classification of mass-transport complexes and distribution of gashydrate-bearing sediments in the northeastern continental slope of the South China Sea. Front. Earth Sci-Prc. 2020, 14, 25-36.

Significant gaps in previous studies are highlighted such as Lines 184-201. Figure 3 represents the classification of submarine landslides in different periods. In the classification shown in Figure 3(a), submarine landslides are categorized into various types of submarine sediment flows [88]. Nevertheless, due to the continuous movement and gradual disintegration of debris, most submarine landslides ultimately transform into sedimentary flows. As depicted in Figure 3(b), this model categorizes submarine landslides into five fundamental types: sliding, tipping, spreading, falling, and flowing [89]. While it essentially encompasses the observed submarine landslide classifications, it does not fully capture the interplay between these types. Masson et al. posit that sliding, debris caving, debris flow, and turbidity currents are the primary modes of failure [90]. Among these, sliding, debris flow, and turbidity currents serve as the principal gravitational driving forces for sediment migration down the slope (Figure 3(c)). Moscardelli and Wood classified Mass Transport Complexes (MTCs) as MTC and turbidity currents. They further divided MTC into sliding, slumping, and clastic flows, as illustrated in Figure 3(d). The authors also described the main features and seismic identification markers of these complexes [91]. Shanmugam et al. highlighted that landslides encompass all forms of mass-transport deposits (MTDs), including sliding, collapse, debris flow, tipping, creep and debris avalanche [92].

 

4, In the discussion section, the research findings are meticulously connected to the broader implications for ocean policy and sustainable development. This section should delve deeply into the significance of the results, comparing them with prior research and discourse. It should also consider the potential ramifications for practical applications and policy-making. Furthermore, the discussion should address any inherent limitations of the study and examine how these constraints might influence the validity and interpretation of the conclusions.

>Response: Thank you for your valuable advice. Firstly, we have explored the significance of the findings and compared them with previous studies and dissertations. Furthermore, we have taken into account the potential impact on practical applications and decision-making. Finally, we have checked the inherent limitations of the study and discussed how they affected the validity of the conclusions.

>Implemented: As shown in Lines 409-419. Additionally, in China, for example, the operating cost of submarine mining in the collection, transportation and smelting process are $40/ton, $60/ton, and $200/ton, respectively. The findings of this study have significant reference value for China in further formulating deep-sea mining policies and can serve as strong theoretical support for Chinese policymakers to enhance the policy of maritime power. Meanwhile, compared with the operating costs of submarine mining in developed countries such as Japan, China's deep-sea mining has more cost advantages, which may play a certain role in promoting future deep-sea mining projects [145]. However, this study is based on the calculation of operational costs in a specific sea area of China, which has certain limitations. Hence, it is necessary to conduct a study on the operational costs of submarine mining in all sea areas of China in the future. As shown in Lines 893-894. Teague, J.; Allen, M. J.; Scott, T. B. The potential of low-cost ROV for use in deep-sea mineral, ore prospecting and monitoring. Ocean Eng. 2018, 147, 333-339.

 

5, The conclusion should succinctly summarize the study's key findings and suggest potential directions for future research. In this section, the conclusion summarizes the core aspects and significance of the research findings in concise terms, and, based on the results, offers recommendations for future research directions or policy adjustments. The content of the response should be precise and moderate in length, avoiding being too brief to omitted important information and not too long to be redundant.

>Response: Thank you for your valuable advice. We have improved the “Conclusions and prospects” section.

>Implemented: As shown in Lines 549-588.

MGH, particularly submarine landslides, have the potential to trigger tsunamis and cause coastal erosion, posing hidden threats to the sustainable development of marine ecosystems and economies. Herein a comprehensive review of the temporal and spatial distribution, classification, character- istics, as well as inductions of submarine landslides. Moreover, it analyzes the safety hazards, environmental pollution, and economic losses that submarine landslides pose to the deep-sea mining industry. Finally, this research summarizes the technical applications and future development directions of submarine landslides. The main conclusions and prospects are as follows:

(1) Submarine landslide hotspots are predominantly concentrated in the Pacific, Atlantic, and Indian Oceans, with notable occurrences in northern Brazil and eastern Venezuela as well as the eastern, western, and southern regions of the United States. The classification criteria for submarine landslides vary. The narrow definition refers to the process of weakly structured rock sliding rapidly along a slope under the influence of gravity, including translational and rotational landslides. Moreover, the broader concept encompasses various sediment transport processes, such as creep, collapse, and gravity flow.

(2) The primary triggering factors of submarine landslides are earthquake and active fault activity (26.82%), rapid deposition (15.61%), and gas hydrate decomposition (7.39%). In deep-sea environ- ments below 1000 m, seismic and active fault activity as well as natural gas hydrate decomposition are considered the two main causes. Moreover, the typical characteristics of submarine landslides typically comprise the head stretch region, body slip region and toe extrusion region.

(3) Based on investigations and predictions of the C-C area of the international seabed, it is believed that China and Mexico are currently the only production bases in the world capable of carrying out large-scale smelting and processing of deep-sea mineral resources, with promising prospects for development. Additionally, we contend that deep-sea mining offers superior economic and environ- mental advantages compared to land-based mining.

(4) The investigation of submarine geological hazards is of great significance to the formulation and implementation of China's marine strategy. Currently, numerical simulation and physical model testing are the primary research methods for submarine landslides. In general, the workflow of ocean engineering necessitates the investigation and assessment of geological hazards, as well as the establishment of risk plans prior to implementation. With the rapid development of China's ocean industry, it is crucial to enhance techniques for identifying and analyzing deep-water landslide disasters, conducting in-situ monitoring, and performing numerical simulations, particularly with regard to deep-sea seabed in-situ monitoring. In the future, we aim to achieve sustainable develop- ment of the marine environment and economy by establishing a multi-level and multi-dimensional monitoring chain that takes into account ecological, environmental and economic factors.

 

6, To enhance the professionalism and readability of the article, professional language editing is essential. Engaging native English speakers or professional editors can ensure a comprehensive text review.

>Response: Thank you for your valuable advice. We have made some language improvements in the manuscript.

>Implemented: As indicated by the red font in the text of the manuscript.

 

7, Ensure that all technical information and data presented in the text are precise and accurate, steering clear of any potential to mislead the reader. It is crucial to clearly articulate the original contributions of the article and to explain how these contributions advance the field by building on or expanding existing research.

>Response: Thank you for your valuable advice. The technical information and data provided in the text have been ensured to be accurate. These can be verified from a large number of references and data materials. In addition, we have clearly articulated the original contributions of the article and explained how these contributions can advance the field by building on or extending existing research.

>Implemented: As shown in Lines 11-29. This paper provides a comprehensive review of sustainable development in marine geological hazards (MGHs), with a particular focus on submarine landslides, the marine environment, as well as the marine economy. Firstly, the novelty of this study lies in reviewing and summarizing the temporal and spatial distribution, systematic classification, inducible factors, and realistic characteristics of submarine landslides to enrich the theoretical concept. Moreover, the costs, risks, and impacts on the marine environment and economy of submarine engineering activities such as oil and gas fields as well as metal ores were systematically discussed. Combined with the current marine policy, an analysis was conducted on the environmental pollution and economic losses caused by submarine landslides. Herein the key finding is that China and Mexico are viable candidates for future large-scale offshore exploitation of oil, gas, nickel, cobalt, cuprum, manganese, and other mineral resources. Compared to land-based mining, deep-sea mining offers superior economic and environmental advantages. Finally, it is suggested that physical model tests and numerical simulation techniques are effective means for investigating the triggering mechanism of submarine landslides, their evolutionary movement process, and the impact on submarine infrastructure. In the future, the establishment of a multi-level and multi-dimensional monitoring chain for submarine landslide disasters, as well as joint risk assessment, prediction, and early warning systems, can effectively mitigate the occurrence of submarine landslide disasters and promote sustainable development of marine environment and economy.

 

8, Minor editing of English language required

>Response: Thank you for your valuable advice. We have made some language improvements in the manuscript.

>Implemented: As indicated by the red font in the text of the manuscript.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

Comments for author File: Comments.pdf

Author Response

Authors’ responses to the comments of Reviewer #4:

 

1, The principal comment is summarized in the following point. The authors write that one in four submarine landslides on the globe occurs as a result of an earthquake impact on a submarine slope. Table 1 of the article under review lists the papers that investigate submarine landslides caused by earthquakes, the articles in Table 1 summarize the methods and results of these papers:

Chen [57] 1988 (soil behavior in submarine landslides: liquefaction, collapse, and slide-sheet).

Kou [59] 1990 (Application of high resolution seismic, 3.5 kHz shallow profile and side sonar seabed scanning, i.e. study of bottom soils in the landslide area).

Jiang and Leblond [60] 1992 (Study of landslide material, the density of the landslide material and the water depth at the site are two crucial parameters).

Zhu [62] 2006 (Three seismic units of submarine landslide in Qiongdong-Yinggehai basin area of South China Sea were studied. Soil Study).

Zhou et al. [69] 2017 (Detailed laboratory experimental study of a soft sensitive marine clay, bottom soil study).

Cheng et al. [70] 2018 (The submarine slope may fail due to the disturbance of the BSR caused by the thrust fault, destruction of sediments containing gas hydrates).

Jiang et al. [71] 2018 (The presence of methane hydrate can increase the strength and decrease the damping of the sediment).

Li et al. [76] 2022 (Slope stability under earthquake impact).

It can be seen that almost all these works are devoted to the research of bottom soil in submarine landslides after the impact of earthquake waves. In the paper under review, nothing is said about the parameters of initial seismic impacts possible in the seas surrounding the coast of China and there are no references to such works. The authors should give the parameters of maximum seismic impacts for the seas of China, as it was done in the work for Northern Eurasia (Ulomov V.I., Shumilina L.S.,

Trifonov V.G. et al. Seismic hazard of orthern Eurasia // Annali di geofisica. 1999. V. 42, N 6. P. 1023-1038) or a separate oil and gas object in the Caspian Sea (Krylov A.A., Ivashchenko A.I, Kovachev S.A. Seismic hazard assessment for oil-and-gasbearing shelf zones: a case study of the North Caspian region // Oceanology. 2015. V. 55. No. 6. P. 910-915). Or the authors should provide references to publications on seismic impacts in the water areas of the East China Sea and the South China Sea. Then the phrase in the abstract of the reviewed article "This review paper provides a comprehensive review of sustainable development in marine geological hazards (MGHs)..." will be reasonable. If such work has not been done in China, it should be stated that such a problem exists and it should be solved.

>Response: Thank you for your valuable advice. We have added Table 1 and relevant references on seismic impacts in the water areas of the East China Sea and the South China Sea.

>Implemented: As shown in the Table 1.

Table 1. Additional references.

Authors	Year	Inducements	Research types	Research contents	Research results
Ruan et al. [65]	2012	Seismic impacts	Numerical simulations	The seismic experiment of 3D array of OBS in the southwestern sub-basin of the South China Sea (SCS).	The results indicate that the spreading ridge in the SCS is experiencing compressive stress caused by seismic shear waves.
Wang et al. [76]	2021	Seismic impacts	Geographic information system	The influence of the initial seismic on the stability of the submarine slope in the South China Sea was studied.	The results indicate that the initial seismic has a significantly uneven impact on the stability of the submarine slopes.
Xie et al. [77]	2021	Seismic impacts	Data analysis	The seismic data of magnitude 4.5 and above in the waters of China and the surrounding areas were fitted.	The results provided empirical formulas to unify magnitude scales for the earthquakes in China's seas and neighboring regions.

Additional relevant references such as Lines 728-729. Ruan, A. G.; Li, J. B.; Lee, C. S.; Qiu, X. L.; Pan, S. J. Passive seismic experiment and ScS wave splitting in the southwestern subbasin of South China Sea. Chinese Sci. Bull. 2012, 57, 3381-3390. Additional relevant references such as Lines 750-753. Wang, Y. X.; Wang, R.; Zhang, J. M. Large-scale seismic seafloor stability analysis in the South China Sea. Ocean Eng. 2021, 235, 109334; Xie, Z. J.; Li, S. Y.; Lyu, Y. J.; Xu, W. J.; Zhang, Y. L. Empirical relations for conversion of surface- and body-wave magnitudes to moment magnitudes in China's seas and adjacent areas. J. Seismol. 2021, 25, 213-233.

 

2, The authors write: "Besides, by establishing a multi-level and multi-dimensional monitoring chain for submarine landslide disasters, as well as joint risk assessment, prediction, and early warning systems, aiming to achieve sustainable management of submarine landslide disasters while taking into account environmental, ecological and economic factors" (lines 27-30).

In my opinion, it is impossible to manage natural disasters like submarine landslides. The authors themselves write that they are inevitable (line 16). Formally, they can be predicted, but not managed. Therefore, this phrase in the abstract should be corrected.

>Response: Thank you for your valuable advice. We have corrected this sentence in the abstract.

>Implemented: As shown in Lines 25-29. In the future, the establishment of a multi-level and multi- dimensional monitoring chain for submarine landslide disasters, as well as joint risk assessment, prediction, and early warning systems, can effectively mitigate the occurrence of submarine landslide disasters and promote sustainable development of marine environment and economy.

 

3, Why is there no tsunami icon in Figure 1c, "The submarine topography and typical MGHs?" Tsunamis are a major category of geologic hazards and the tsunami icon should be placed on the diagram.

>Response: Thank you for your valuable advice. In Figure 1(c) earlier, we used "Seaquake" to indicate a "Tsunami". However, we have now updated the tsunami icon in Figure 1(c).

>Implemented: As shown in the Figure 1(c).

 

Figure 1(c) The submarine topography and typical MGHs.

 

4, The authors write "Oil spill problems: the presence of oil and gas reserves beneath the seabed is not typically impacted by submarine landslides, however, research indicates that such events can have detrimental effects on these resources (Figure 6(a)" (lines 286-288). It does not appear from Figure 6a that the presence and/or production of oil and gas at sea affects or is affected by submarine landslides. The authors should provide explanations for this text and Figure 6(a).

>Response: Thank you for your valuable advice. We have provided an explanation of the text and Figure 6(a).

>Implemented: As shown in Lines 292-295. (1) Oil spill problems: the presence of oil and gas reserves beneath the seabed is not typically impacted by submarine landslides (Figure 6(a)). Nevertheless, studies have shown that submarine landslides can cause significant damage to the transportation of oil and gas in the ocean [117].

 

5, The authors write: "The primary triggering factors of landslides are earthquake and fault activity (26.82%), rapid deposition (15.61%), and gas hydrate decomposition (7.39%)" (lines 552-553).

How can faults cause landslides? Landslides can be caused by earthquakes that are confined to faults. But there are inactive faults along which earthquakes do not occur. Therefore, it is incorrect to write that faults are the cause of landslides. Perhaps the authors meant slow displacements of fault wings, which can lead to landslides. Therefore, the text of the article in this place should be corrected.

>Response: Thank you for your valuable advice. We have explained how a fault can lead to a seabed landslide. In detail, we have revised the text to include the term 'active fault' instead of 'fault', in order to enhance accuracy.

>Implemented: As shown in Lines 231-244. (1) Earthquake and active fault activity: Active fault activity can increase the dip angle of the submarine slope body and transfer energy from the underlying bedrock to the seabed surface sediments, which not only amplifies the shear force of the slope body, but also diminishes the strength of the soil mass due to vibration liquefaction. Mean- while, the active fault serves as a crucial conduit for natural gas migration, enabling deep-seated gases to ascend along the active fault plane and facilitate the development of potential slip surfaces [102]. On the other hand, while submarine earthquakes can directly induce slope instability, they also have the potential to trigger tsunamis that exacerbate such instability. In the northern part of the South China Sea, a multitude of large active faults have developed at the base of the Baiyun seabed landslide, extending vertically for thousands of meters. The seismic reflection characteristics of the strata exhibit polarity reversal and high amplitude anomalies, which are distributed on both sides of or at the top of the active fault plane, potentially serving as a primary trigger for landslide disasters [103].

As shown in the Figure 5.

Figure 5. Triggering factors of submarine landslides [101].

As shown in Lines 565-570. (2) The primary triggering factors of submarine landslides are earth- quake and active fault activity (26.82%), rapid deposition (15.61%), and gas hydrate decomposition (7.39%). In deep-sea environments below 1000 m, seismic and active fault activity as well as natural gas hydrate decomposition are considered the two main causes. Moreover, the typical characteristics of submarine landslides typically comprise the head stretch region, body slip region and toe extrusion region.

 

6, What does this phrase mean "In the future, we aim to achieve sustainable development of marine landslide disasters...". (line 577-578). It can be understood that the authors are going to develop marine landslide disasters. This phrase should be rewritten in more understandable language.

>Response: Thank you for your valuable advice. We have improved this sentence.

>Implemented: As shown in Lines 585-588. In the future, we aim to achieve sustainable development of the marine environment and economy by establishing a multi-level and multi-dimensional monitoring chain that takes into account ecological, environmental and economic factors.

 

7, The authors write: "The sea is a harsh environment: the once-in-a-century wind waves induced by marine earthquakes are as high as 12.9 m, which is comparable to the Gulf of Mexico and three times the size of the waters off West Africa" (lines 299-301).

The authors need to ask the question: in which paper are wind waves induced by 12.9 m high marine earthquakes described? They cannot be the subject of study in the paper on corrosion behavior of a new-type weathering steel used in harsh marine environment to which the authors refer in the reference list (Jia, J.H.; Cheng, X.Q.; Yang, X.J.; Li, X.G.; Li, W. A study for corrosion behavior of a new-type weathering steel used in harsh marine environment. Constr. Build. Mater. 2020, 259, 119760). The authors need to cite the primary source where such waves were studied. Then perhaps the nature of wind waves induced by marine earthquakes would be understood. I have heard nothing about such waves. They're physically impossible. Maybe they mean seaquakes (stationary waves on the water), but what does wind have to do with it? The text needs to be revised.

>Response: Thank you for your valuable advice. We have removed this section.

>Implemented: As shown in Lines 293-304. (1) Oil spill problems: the presence of oil and gas reserves beneath the seabed is not typically impacted by submarine landslides (Figure 6(a)). Nevertheless, studies have shown that submarine landslides can cause significant damage to the transportation of oil and gas in the ocean [117]. The deep-water horizon explosion in the Gulf of Mexico in 2010, which resulted in the loss of 11 lives and the release of millions of barrels of oil into the ocean, is considered one of the worst marine disasters in American history [118,119]. The South China Sea boasts abundant oil and gas reserves in its deep waters. In the deep water area at a depth of 300 m, there are proven geological reserves of approximately 8.304 × 10⁹ t of oil and geological resources of about 7.493 × 10⁹ m³ of natural gas [120]. The exploration and exploitation of deep-water oil and gas resources in the South China Sea holds significant importance for alleviating China's reliance on imported oil and enhancing its economic security coefficient.

Author Response File: Author Response.pdf

Round 2

Reviewer 4 Report

Comments and Suggestions for Authors

Comments for author File: Comments.pdf