Marine Geo-Hazards in China

By Yin-can YE

Marine Geo-Hazards in China, the first book to focus specifically on potential marine geological hazards in China, includes 19 chapters with varying focus on key issues surrounding the topic.Early chapters discuss the historical background, research progress, and geological environments in China's sea area. Next, multiple chapters present special topics on geological hazards in China's sea area, including its disaster pregnant environment, mechanisms of disaster change, the development regularity and disaster formation process, and existing or potential dangers and countermeasures. Final chapters present the latest information on the distribution, development, assessment, and risk analysis of marine geological hazards.This book is an important source of information for government and local policymakers, environmental and marine scientists, and engineers.

• Discusses the background, current research, and systematically reviews the history, major advances in the studies in the field, and demonstrates the development prospect of this subject
• Contains and summarizes the author’s longstanding achievements in the field, as well as includes a wide range of researches conducted both locally and overseas
• Systematically summarizes the basic characteristics of the distribution and development of the main types of geological hazards in China seas
• Puts forward the scheme of marine geological disaster regionalization of China, and is significant for researches in other countries or regions

• Language: English
• Publisher: Elsevier Science
• Release date: Jun 22, 2017
• ISBN: 9780128128121

Yin-can YE

Professor Ye graduated from the Department of Geology, Nanjing University in 1966. He works as the General Engineer of Second Institute of Oceanography, State Oceanic Administration, China, with more than 40-years’ experience on marine engineering geology, engineering geophysics, oceanography, and application research in key technology of ocean engineering construction. He led many researches on marine geo-hazards, marine environment and safety engineering, seafloor detection, and in-situ test techniques. Until now, Prof. Ye published more than 90 papers and 3 books, edited 2 national technical standards.

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Marine Geo-Hazards in China

Ye Yincan et al.

Table of Contents

Cover image

Title page

Copyright

List of Contributors

Foreword

Preface

Acknowledgments

A Brief Introduction

Chapter 1. Introduction

1. Concept and Connotation of Geological Hazards

2. Background of Emergence and Development of Marine Hazard Geology

3. Object and Content of Study of Marine Hazard Geology

4. History Review and Main Progress of Study on Marine Geological Hazards

5. Development Prospects of Marine Hazard Geology

Chapter 2. Marine Geographic and Geological Environment of China

1. General Geography Situation of the China Seas

2. Marine Meteorology and Hydrology

3. Submarine Topography and Landforms

4. Submarine Sediment Types and Distribution Characteristics

5. Seabed Geological Tectonic Environment

Chapter 3. Classification of Marine Hazard Geology Factors and Marine Geological hazards

1. Classification Principles and Scheme of Marine Hazard Geology Factors

2. Classification and Gradation Principle and Scheme of Marine Geohazards

Chapter 4. Active Faults of Sea Area

1. Types and Identification Marks of Active Faults

2. Active Faults of China Seas

3. Sea Active Fault Hazards and Their Engineering Evaluation

Chapter 5. Sea Earthquake and Earthquake Tsunami

1. Sea Earthquake Hazards

2. Earthquake Intensity and Acceleration

3. Earthquakes of China Seas

4. Seismic Safety Evaluation for Marine Engineering Sites

5. Earthquake Tsunami and Its Forecast

Chapter 6. Submarine Landslides

1. Research Progress of Submarine Slope Stability

2. Classification and Characteristics of Submarine Landslides

3. Origin and Dynamic Mechanism of Submarine Landslides

4. Methods for Subsea Slope Stability Analysis

5. Submarine Landslides and Their Distribution Characteristics of China Seas

Chapter 7. Coastal Erosion

1. Coastal Environment and Classification

2. Coastal Erosion and Its Causes

3. Prevention and Treatment of Coastal Erosion

Chapter 8. Local Scour and Protection of Marine Structures

1. Local Scour Phenomenon and Its Engineering Hazard

2. Mechanism of Local Scour

3. Basic Methods of Study on Foundation Scour of Offshore Structures

4. Analysis of Foundation Scour Stability and Its Engineering Protection of Offshore Structures

Chapter 9. Seabed Sand Liquefaction and Evaluation

1. Concept and Formation Mechanism of Sand Liquefaction

2. Influence Factors of Sand Liquefaction

3. Analysis and Evaluation of Sand Liquefaction

4. Analysis of Potential Liquefaction Areas in China Offshore

5. Engineering Evaluation and Prevention of Liquefaction

Chapter 10. Submarine Turbidity Current

1. Establishment and Development of Turbidity Current Theory

2. Formation Mechanism of Submarine Turbidity Current

3. Dynamic Process of Submarine Turbidity Current

4. Distribution Characteristics of Turbidity Current of China Seas

5. Influence Factors of Submarine Turbidity Current Formation

6. Engineering Harmfulness and Preventive Measures of Submarine Turbidity Current

Chapter 11. Submarine Shallow Natural Gas

1. Type and Basic Characteristics of Shallow Natural Gas

2. Storage Form and Identification Marks of Shallow Natural Gas

3. Distribution Characteristics of Shallow Natural Gas of China Offshore

4. Hazard Mechanism and Preventive Measures of Shallow Natural Gas

Chapter 12. Submarine Sand Waves and Sand Ridges

1. Dynamic Environment of Continental Shelf and Bedform Types

2. Submarine Sand Waves

3. Submarine Sand Ridges

4. Activity and Engineering Harmfulness of Sandy Bedform of Continental Shelf

Chapter 13. Special Geological Bodies

1. Submarine Mud Diapir and Mud Volcanoes

2. Coral Reef

3. Submarine Ancient River Channel

Chapter 14. Sea Level Change, Sea Water Intrusion, and Coastal Land Subsidence

1. Sea Level Change

2. Seawater Intrusion

3. Land Subsidence in Coastal Areas

4. Current Situation and Development Trend of Hazards in China River Delta Areas

Chapter 15. Development Laws of Geological Hazards and Hazard Geology Regionalization of China Seas

1. Type and Regional Distribution Characteristics of Main Hazard Geology Factors of China Seas

2. Basic Characteristics of Geological Hazards of China Seas

3. Regionalization of Hazard Geology of China Seas

Chapter 16. Marine Geological Hazard Prevention and Social Economic Sustainable Development

1. Marine Geological Hazards Situation Evaluation

2. Marine Geological Hazards Alleviation and Prevention

3. Hazards Alleviation and Prevention and Sustainable Development of Society and Economy

References

Index

Copyright

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List of Contributors

Ye Yincan

Second Institute of Oceanography, State Oceanic Administration, Hangzhou, China

Zhejiang University, Hangzhou, China

Lai Xianghua

Second Institute of Oceanography, State Oceanic Administration, Hangzhou, China

Zhejiang University, Hangzhou, China

Pan Guofu

Second Institute of Oceanography, State Oceanic Administration, Hangzhou, China

Zhejiang University, Hangzhou, China

Li Qitong,     Jiangsu Institute of Earthquack Engineering, Nanjing, China

Zhuang Zhenye,     Ocean University of China, Qingdao, China

Liu Dujuan,     Second Institute of Oceanography, State Oceanic Administration, Hangzhou, China

Chen Xiaoling,     Second Institute of Oceanography, State Oceanic Administration, Hangzhou, China

Wei Yanji,     University of Groningen, Groningen, Netherlands

Chen Junren,     Guangzhou Marine Geological Survey, Ministry of Land and Resources, Guangzhou, China

Hu Taojun,     Second Institute of Oceanography, State Oceanic Administration, Hangzhou, China

Chen Xitu,     Second Institute of Oceanography, State Oceanic Administration, Hangzhou, China

Zhan Wenhuan,     South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China

Li Quanxing,     Second Institute of Oceanography, State Oceanic Administration, Hangzhou, China

Tian Shuangfeng,     Second Institute of Oceanography, State Oceanic Administration, Hangzhou, China

Li Dong,     Second Institute of Oceanography, State Oceanic Administration, Hangzhou, China

He Xin,     Second Institute of Oceanography, State Oceanic Administration, Hangzhou, China

Foreword

For more than a century, because of the global population explosion, excessive consumption of natural resources, a large number of emissions of waste, the climate has been warming, sea level rising, and the ecological balance destroyed. Human society is faced with major issues of environmental deterioration. One of the important signs of the deterioration of environment is that the natural hazards are becoming more and more frequent, which poses a serious threat to the survival and development of humankind. Geological hazards as one of the main types of natural hazards has become the important factor influencing and restricting the social and economic development that can't be ignored; it has earned a great deal of attention from the governments and the scientific community's workers.

China is not only one of the countries with the most severe geological hazards but also one of the few countries that have very serious marine geological hazards of many types, high frequency, wide distribution area, and big hazard losses. With the rapid development of China's marine economy, harmfulness of marine geological hazards is rapidly increasing, and the necessity and urgency of preventing and reducing the marine geological hazards is becoming more and more obvious.

The authors of Marine Geo-Hazards in China, profoundly discuss the historical background of this subject, and systematically summarize the survey and research results and progress in recent decades in the field of marine geological hazards. They especially discuss the hazard-prone environment, catastrophe mechanisms, development regularity and hazard process, engineering hazards and prevention, and control of the main types of geological hazard in China seas. The book briefly summarizes the basic characteristics of distribution and development law of marine geological hazards, and introduces marine hazard geology regionalization for China seas.

The book is rich in content, and brings together the representative of the latest research results. It can be as a useful reference for the professionals of all countries engaged in marine geology, environmental geology, ocean engineering and disaster prevention engineering. Publication of this English version of the book will provide an opportunity for mutual communication, sharing in knowledge and experience.

Chen Jiyu,     Academician of Chinese Academy of Engineering

September 2016

Preface

Human society is facing a severe challenge of the sharp expansion of population, the shortage of resources and with the ever-worsening environment. One of the important signs of the deterioration of the environment is that natural hazards are becoming more and more frequent, and they pose a serious threat to the survival and development of humankind. Geo-hazard refers to the natural, artificial, or synthetic geological processes that cause geological environment deterioration, and lead to human life and property damage; these events seriously damage the resources and environment on which human survival depends. Geological hazards, as one of the main types of natural hazards, have become an important factor influencing and restricting the social and economic development and cannot be ignored; they have already gained a great deal of attention from the governments of all countries and the international scientific community throughout the world.

The earth is the common home of humankind, and the sea is the basic condition that makes this home maintain its vigor; it provides precious wealth and vast space for the sustainable development of human society and it is the strategic resource base of the energy, minerals, food, and fresh water. In the long history of human development, the ocean had close relationship with economy and social development. The rapid development of modern marine science and technology will raise our understanding for the ocean and ability to develop the ocean to an unprecedented level. Since the 1970s, the total output value of the world's marine industry has increased by a speed of two times in about every 10  years. It can be asserted that the world's maritime economy in the future will continue to develop rapidly. China is a large maritime country with a long coastline and a vast sea land. After the founding of new China, especially since China's opening to the outside world in the 1980s, China has made considerable progress in the development and utilization of marine resources and development of marine economy. The national output value of the marine economy has grown from 8  billion RMB in 1980, to 413.3  billion RMB in 2000, to 3843.9  billion RMB in 2010, and to 5993.6  billion RMB in 2014. The national marine economic output ratio in the GDP has increased from 2.6% in 2000 to 9.4% in 2014; thus, the marine economy has become the new growth point of the national economy.

China is one of the countries that has the most serious geological hazards in the world. Every year earthquakes, collapses, landslides, debris flow, land subsidence, land desertification, and other hazards cause huge economic losses. China's marine geological hazards have caught the attention of the world. Frequent or bursts of all kinds of marine geological hazards, especially the coastal geological hazards, bring heavy losses to the densely populated and economically developed coastal areas, and they inhibit these regions' economic and social sustainable development. According to the marine hazard statistical bulletin released by the State Oceanic Administration of China, from 1989 to 2014, storm surges, red tides, sea waves, sea ice, and other marine hazards have caused economic losses amounting to 326.9  billion RMB, and the number of deaths and missing was 6905 people.

The 42nd United Nations General Assembly defined the last 10  years in the 20th century as the International Mitigate Natural Hazards for 10 Years. The Chinese government has set up the National Commission for Natural Hazard Mitigation, and has strengthened the investment, coordination, and leadership in disaster reduction. Compared with land geological hazards, marine geological hazard investigation and research work had a late start, but with the rapid expansion of exploration and development of offshore oil and gas and other mineral resources since the 1980s, marine engineering facilities are fast increasing, and marine geological hazard investigation and research has become one of the most important issues for the marine engineering construction preparatory work. Strengthening China's marine geological hazard investigation and research work, establishing and making perfect the marine geological hazard prediction, early warning, and forecasting system is a long-term and arduous task with very important strategic significance.

This book discusses the historical background of the emergence of marine hazard geology, and the main research progress that has been made, puts forward the classification scheme of marine hazard geology factors and marine geological hazards, focusing on the representative marine geological hazards in China Seas as the special topic. The content of the special topics mainly includes all kinds of hazard pregnant environment, hazard mechanisms, regularity of development and hazard formation process of marine geological hazards, existing or potential risks, and countermeasures against them. For every special topic presented, there is a summary of the basic characteristics of distribution law and development of the main geological hazard types, putting forward the hazard geological regionalization scheme of China Seas, and marine geological hazards assessment and risk analysis method, and provides the scientific basis for marine geological hazard mitigation and prevention.

This book at the time of writing extensively refers to the investigation and research results of China Geological Survey Bureau, State Oceanic Administration, departments of Chinese Academy of Sciences and other relevant departments, and fully adopts the valuable information obtained from a number of major oil and gas engineering and subsea communication engineering surveys in the China Seas, striving to fully reflect the latest progress of China in the field of marine geological hazards, and expecting to play a positive role in promoting long-term development and progress of this field.

Ye Yincan

September 2016

Acknowledgments

Professor Chen Jiyu, China's famous scientist in the field of coast and estuary science, academician of the Chinese Academy of Engineering, in spite of being very busy wrote the foreword for this book. In the process of writing the book, we have the enthusiastic support and help from Professor Jin Qinghuan, academician of the Chinese Academy of Engineering; Professor Yang Zuo-sheng, of Ocean University of China; and Professor Liu Cang-zi, of East China Normal University; and others. To all of them, we together express our gratitude!

This book extensively refers to the investigation and research results of the Chinese Geological Survey Bureau, State Oceanic Administration, Chinese Academy of Sciences and other relevant departments, fully adopts the valuable information obtained in a number of major oil and gas engineering and submarine communication engineering surveys in China seas, refers to a large number of scientific and technological papers, books, current technical standards, and other information. Hereby we sincerely thank the authors whose literature is cited!

The book consists of 16 chapters, of which Chapter 1 is written by Ye Yincan; Chapter 2 is written by Li Quanxing, Chen Xitu, Chen Xiaoling, and Li Dong; Chapter 3 is written by Ye Yincan; Chapter 4 is written by Li Qitong and Hu Taojun; Chapter 5 is written by Li Qitong, Hu Taojun, and Ye Yincan; Chapter 6 is written by Lai Xianghua; Chapter 7 is written by Zhuang Zhenye; Chapter 8 is written by Wei Yanji and Ye Yincan; Chapter 9 is written by Chen Xiaoling; Chapter 10 is written by Chen Junren; Chapter 11 is written by Pan Guofu; Chapter 12 is written by Zhuang Zhenye and Ye Yincan; Chapter 13 is written by Chen Xitu, Zhan Wenhuan, and Ye Yincan; Chapter 14 is written by Liu Dujuan; Chapter 15 is written by Ye Yincan, Chen Junren, Liu Dujuan, and Tian Shuangfeng; Chapter 16 is written by Liu Dujuan. Maps and drawings computer processing is done by Tian Shuangfeng and He Xin. Ye Yincan is responsible for the planning, unified draft, validation of the whole book.

Ye Yincan

September 2016

A Brief Introduction

This book is the first monograph of marine hazard geology in China. The book is divided into 16 chapters. Chapters 1–3 discuss the historical background of the marine hazard geology, research progress, and hazard geology environments in China waters, puts forward the classification scheme of marine hazard geology factors and marine geological hazards. Chapters 4–14 provide detailed discussion on the main marine hazard geology factors in China waters; the topics of these special discussions mainly include all kinds of hazard prone environments, mechanisms, development laws and processes of marine geological hazards, and existing or potential dangers and countermeasures.Chapter 15 briefly introduces the distribution law and basic characteristics of development of marine geological hazards in China waters, and puts forward the regionalization of marine hazard geology. Finally, Chapter 16 discusses the hazard assessment and risk analysis method of marine geological hazards, which provides a scientific basis for hazard reduction and prevention of marine geological hazards.

This book is of great benefit to the professional scientific and technical personnel specializing in marine geology, environmental geology, marine engineering, and hazard prevention engineering, and also for the teachers and students in relevant colleges and universities.

Chapter 1

Introduction

Abstract

This chapter introduces the basic concept and connotation of geological hazard, expounds on the historical background of emergence and development of marine hazard geology and its study subject and content, reviews the main progress of research in the field of marine geological hazards in detail, and forecasts the future development prospects of the subject.

Keywords

Geological hazards; Global change science; Hazard assessment; Hazard prevention and reduction; Marine geological hazards; Marine hazard geology

Chapter Outline

1. Concept and Connotation of Geological Hazards

1.1 The Basic Meaning of Hazards

1.2 Geological Hazard and Its Connotation

1.3 Geological Hazard and Hazard Geology Factor

2. Background of Emergence and Development of Marine Hazard Geology

2.1 The World Is Facing the Serious Challenges of Environmental Problems

2.2 The Great Concern of the International Community and the Governments of the World to the Global Environmental Problems

2.3 Scientific Background of Marine Hazard Geology Development

3. Object and Content of Study of Marine Hazard Geology

3.1 Types of Marine Geological Hazards

3.2 Formation Conditions and Genetic Mechanism of Marine Geological Hazards

3.3 Developmental Laws and Hazard Developing Process of Marine Geological Hazards

3.4 Zoning of Marine Hazard Geology and Risk Evaluation of Marine Geological Hazards

3.5 Hazard Assessment of Marine Geological Hazard

3.6 Monitoring, Prediction, and Prevention of Marine Geological Hazard

4. History Review and Main Progress of Study on Marine Geological Hazards

4.1 Historical Review

4.2 Main Research Progress

4.2.1 Classification of Marine Hazard Geology Factors and Marine Geological Hazards

4.2.2 Studies of Gradually Varied Marine Geological Hazards

4.2.3 Studies of Major Burst Marine Geological Hazards

4.2.4 Marine Geological Hazard Assessment and Hazard Prevention and Mitigation Study

5. Development Prospects of Marine Hazard Geology

5.1 Integrate into the Global Change and Global Change Science Concept

5.2 Strengthen Basic Theory Research of Marine Hazard Geology

5.3 Emphasize Coastal Geology Hazard Research

5.4 Promote the Scientific Problems and Key Technology Research for Marine Geological Hazard Prevention

5.5 The Extensive Application of High Technology

5.5.1 Application of Information Technology

5.5.2 Application of Sea Bottom Cable Observation Network

1. Concept and Connotation of Geological Hazards

1.1. The Basic Meaning of Hazards

The definition given to hazards by the United Nations Disaster Relief Organizations is: a concentrated accident in time and space, and during the accident the local human population and their property face serious threat and make enormous losses, and the family structure and social structure have also been enormously influenced. United Nations disaster management training materials clearly define hazard as serious damage to human life and property and activities and other social functions in natural or man-made environments, which bring widespread life, material, or environmental losses, and these losses are beyond the capability of the influenced society to resist by depending on its own resources.

Visual hazards are the catastrophic events led by natural factors or human factors; they bring harm and destruction to human life and property and resources and environment on which humans rely to survive.

According to the conditions present, hazard can be divided into two categories: natural and man-made. The kinds of natural hazard are very various, they have spatial distribution and different forms, and their formation conditions include two aspects: the first is the natural dynamic process or abnormal change of natural environment; the second is the affected objects by the hazard, that is human life and property as well as the resources and environment on which humans rely to survive and for development. During a hazard event, the former can be called the hazard-caused body, and the latter can be called the hazard-bearing body, or the victim body.

The influence of hazards to humans doesn't happen only at the moment that disastrous geological events occur; some hazards may have long-term negative effects on human beings. Therefore, the effects of hazard can be divided into the original effects, the secondary effects, and the subsequent effects. The original effects are caused by the hazard events themselves, such as during an earthquake buildings collapse, landslides bury houses, and there are mine gas explosion casualties and others caused by the ground motion. The secondary effects are caused by the hazard process that is induced by the major hazard events; they have no direct relation with the major hazard event itself, such as fire due to gas pipeline rupture during an earthquake, water scarcity caused by water supply system interruption due to floods, building collapse caused by the earthquake, which is induced by large karst collapse. The subsequent effects tend to be long term or even permanent, and these effects include the extinction of wildlife, channel changes caused by floods, regional or global climate change, agricultural production losses after a volcanic eruption, and terrain changes due to earthquakes, etc.

The effects of hazards to humans can be divided into direct loss and indirect loss. Direct loss (or directly influence) refers to the immediate consequences after an event, such as casualties and property losses due to building collapse in the earthquake. It is caused by the direct destruction by hazards to human beings and their property and the environment, and in most cases it can be measured by accurate and reliable monetary value. Indirect loss (or indirect influence) refers to the secondary consequences in a hazard, such as famine and disease spread brought by a hazard, a reduction in consumer purchases, output reduction from factory falling production, increased unemployment, and others. In addition, the spiritual trauma of the affected population due to scare and loss of loved ones also belongs to indirect loss of hazard. The influence of indirect loss lasts much longer than the influence of direct loss, and this effect is intangible and not easy to calculate using monetary value.

1.2. Geological Hazard and Its Connotation

The Ministry of Land and Resources of the People's Republic of China's industry standard Geological Hazard Classification defines geological hazard as: the unfortunate geological event in which earth brings harm to human life and property, the destruction of production or damage to the resources and environment on which humans rely to survive and develop under internal and external power or human engineering activities. Therefore, geological hazard refers to the disastrous geological events under various natural geological processes or human activities during the evolution of the earth's development process. The distribution and variation of geological hazard in space and time is not only subject to the natural environment but also related to human activities, and the latter is often the interaction consequence of human and the geological environment. Generally, geological hazards are the phenomena or events in which geological changes (natural, man-made, or synthetic) make the geological environment produce sudden or gradual destruction, and cause loss of human life and property. Geological hazard, meteorological hazard, and biological hazard are some of the main types of natural hazard, and they have the characteristics of sudden, multiple, mass, and gradient effect. Because geological hazard often causes serious casualties and huge economic losses, it occupies a prominent position in the category of natural hazard.

By definition of the connotation of geological hazard, geological hazard includes two aspects, dynamic conditions of hazard and hazard event consequences.

Geological hazard is caused by geological processes, including internal dynamic geological processes and external dynamic geological processes. As the scale of human activities unceasingly expands, the influence of human activities on the form the earth's surface and substance composition increases, so in the processes of the geological hazards, human activities on the earth's surface system are also included, which are artificial geological processes.

Only the geological events causing influence or damage to human life and property and the living environment are called geological hazards. If a certain geological process simply deteriorates the geological environment and there is no damage to human life and property or it does not affect the production, living environment, then it can only be described as a catastrophe. For example, collapse, landslide, and debris flow occurring in the deserted area will not cause human life and property damage, so this kind of geological event belongs to catastrophic geological events; if these collapses, landslides, and debris flows occur in the social economy developed area, it brings different degrees of casualties (or) property losses, which are called hazards.

Geological hazard is a natural phenomenon, and it also has serious impact on the production of human society and life. So it not only has natural but also social attributes. Natural attributes refers to various kinds of natural characteristics related to dynamic processes of geological hazard, such as scale, intensity, frequency, incubation conditions, and the change law of the hazard activity. Social attributes mainly refers to the human society characteristics that are closely related to the hazard activities, such as distribution of population and property, construction activities, resources development, economic development level and the ability apply hazard prevention, etc. Since the geological hazard is the result of the interaction between natural processes and social and economic activities of humans, they are unified.

Marine geological hazards are the disastrous events caused by a variety of natural geological processes and human activities in the evolution process of the earth's development; the different types of marine geologic hazards have their own laws, and are not only restricted by the earth and ocean environments, but also closely related to the human activities that develop and use the oceans. Marine geological hazard is one kind of natural disaster. It is the biggest hazard on the development of marine economy, and all countries are very concerned about it and are putting a lot of manpower, material resources, and funds into multiple aspects of research.

1.3. Geological Hazard and Hazard Geology Factor

What is hazard geology factor? What is geological hazard? There is still confusion in current academic circles, and no uniform understanding of these terms. Hazard geology factor and geological hazard are two special terms, and there are relations and differences between them, with different properties and tasks (Liu et al., 2000a).

Geological hazard for the affected object may be accidental and random. However, as a kind of geological process, most of it is normal and inevitable. The activity law of geological process as geological hazard factor is controlled by geology, natural geography, and the environment. Because human activities are involved in the geological effects, humans have obvious influence on geological hazard, but it also will play a role through the geological law. When we study the development law of geological hazard factor, we can ignore the social attributes of it, and collectively refer to the similar geological factors as hazard geology factor. Hazard geology factor not only includes the hazards that have occurred but also the hazards that never happen and potentially dangerous factors. In fact, geological hazard investigation and study cannot be limited to the geological hazard that has already formed; more important are those hazards that have not yet happened or potentially dangerous geological hazard factors. The study of the formation and development of geological hazards has very important meaning for forecasting, prevention, and control of geological hazards. Hazard geology factors have diverse forms, including some geological bodies (such as liquefied sand soil, diapir, fault, ancient river channel), geological processes (such as coastal erosion, turbidity, earthquake, sea level rise), and geological conditions (such as vulnerable lowlands).

2. Background of Emergence and Development of Marine Hazard Geology

Hazard geology is an important branch of geology. It is a new interdisciplinary science between disaster science and geology, and as a science, its specialized research has just started. The emergence and development of hazard geology is inseparable from the need to solve the problem of environmental hazard, and it has serious social and scientific background.

2.1. The World Is Facing the Serious Challenges of Environmental Problems

The formation of the earth has been billions of years; every hour and moment it changes by its natural development law. Human survival depends on the earth resources and environment, and in the history of human development, the influence of humans on the earth's resources and environment in general is very small. The improvement of productivity pushed forward the development of human society but also increased human interference on nature. Especially since the industrial revolution in the 19th century, social economies have rapidly developed, population rapidly expanded, and production and urbanization scales increasingly expanded. Forests have been cut down in large numbers, grasslands have been excessively grazed, desertification has been increasingly expanded, resources have been excessively consumed, wastes have been increasingly emitted, species extinction is thousands of times the natural rate, and the earth's landscape and environment have suffered big changes by humans with unprecedented speed and scale. The greenhouse effect made global warming, causing sea levels to rise, El Nino to happen frequently, and geological hazards such as land subsidence, seawater intrusion, groundwater pollution, flood and debris flow to be rampant. The ecological environment is under destruction. The earth's environment is deteriorating rapidly, which is a serious threat to human survival and the development of social economies—the world is facing serious challenges from environmental problems.

Geological hazard is one of the main types of natural disasters, and historically it has brought endless pain to humans, leaving many painful memories, so it is the environmental issues that are of the most concern to people. Most of the environmental problems described previously are geological environment problems or geological hazard problems, which gives geology new tasks, and also provides conditions for the development of hazard geology.

2.2. The Great Concern of the International Community and the Governments of the World to the Global Environmental Problems

On June 5, 1972, the United Nations Conference on the Human Environment was held in Stockholm, Sweden; more than 1300 delegates from 113 countries gathered together for the first time to discuss the global environmental problems. This conference passed the epoch-making document Declaration of the United Nations Conference on the Human Environment, and it was a sign of the mutual human concern on environmental problems. In 1987, the World Commission on Environment and Development led by the prime minister of Norway, Gro Harlem Brundtland, first expounded on the concept of sustainable development in the Our Future report. In 1992, the United Nations Conference on Environment and Development passed Rio Declaration, which made an epoch-making action plan, Agenda 21. The year 2002 was the 10th anniversary of Rio de Janeiro Earth Summit, and the United Nations held the memorial meeting in Johannesburg, South Africa, with more than 100 heads of state or government attending; it proposed the Implementation of the Plan of the World Summit on Sustainable Development. The world summit in 2005 signed the United Nations Millennium Declaration, reaffirming the principle of sustainable development agreed on at the environment and development conference.

Agenda 21 takes ocean as an important part, of which the 17th chapter puts forward the following: the marine environment—including ocean and marine and coastal areas adjacent is as a whole, and it is a basic component of the global life support system, it is also a kind of precious wealth to contribute to the realization of sustainable development. The fourth part of Implementation of the Plan of the World Summit on Sustainable Development: protect and manage basic natural resources required for economic and social development, and it proposed an action plan in the field of ocean; this plan also identified targets with a time limit for the marine ecosystems, marine fishery, marine protected areas, and marine environment.

Development is the theme of the progress of human society, and the idea of sustainable development has gradually formed in the human cognition process for the increasingly serious ecological environment problems. Economic development, social progress, and environmental protection are related and promoted mutually, and together constitute the three pillars of sustainable development. Agenda 21 and Implementation of the Plan of the World Summit on Sustainable Development as a milepost-type international document present the status and role of the ocean in global sustainable development. Since 1997, the Secretary General of the United Nations every year has submitted an Oceans and the Law of the Sea report to the UN General Assembly, giving a more comprehensive summary of the marine environment, marine resources, and sustainable development actions and progress for the year.

The United Nations and other international organizations and governments around the world, great public concern for environmental issues, and an effective global action plan provide good development conditions for the environmental discipline, including marine hazard geology.

2.3. Scientific Background of Marine Hazard Geology Development

Since the 26th session of the International Geological Congress put forth a statement of geological environment problem in 1980, more and more scientists in the field of earth science are deeply aware that one direction of the geological science development is mainly the participation in the solution of environmental problems and hazards of the earth. How to prevent and control the environmental deterioration of the geological hazards and human factors existing in nature, and how to take measures to protect the existing living environmental problems are key problems in the field of environmental geology study.

Environmental geology is almost synchronous with the development of environmental science. Environmental science is the science that explores environmental evolution law in the global scope, reveals the relationship between human activities and natural ecology, and explores the effects of environmental changes on human survival, and researches the technical measures and management measures for the comprehensive prevention and control of regional environmental pollution; it is spread across the natural sciences and social sciences, and is a comprehensive scientific cluster. Because the current environmental change is global, the mechanism of this change is very complex, and not a single science can solve the issues. Based on this fact, in 1983 the World Science Association Conference proposed a global change concept. Very soon the global change science research became the mainstream of international environmental science, and a new discipline was formed, called global change science. It takes the complex nonlinear multicoupled earth system as the research object, treats the atmosphere circle, hydrosphere circle, lithosphere circle, and biosphere circle (including human beings) as a whole, and investigates the physical, chemical, and biological processes between the various components of the system, with particular attention to human impact on the earth's environment. Since the 1980s, global change research has formed four major interdisciplinary comprehensive research plans, namely the international geosphere circle/biosphere circle program (IGBP), the world climate research program (WCRP), plan for the human factor in the global change (HDP), and biological diversification program (DIVERSITAS).

Global environmental change involves many aspects, but the present hot spot is still climate change and sea level rise. The ocean is the main body of the hydrosphere, and it interacts with other earth spheres. The ocean is a treasure house of resources, and it is the main object of human development and utilization now and in the future. The coastal zone is the most active and frequent area with developed social and economic activity and human activity of coastal nations; it is the zone with mutual infiltration and influence between the atmosphere circle, hydrosphere circle, lithosphere circle, and biosphere circle; the interaction process of sea and land is complex, and it has characteristics that are sensitive to the change of the environment and fragile to hazard. Obviously, because of the importance of the ocean to humans and its sensitivity to global changes, marine environmental science plays an irreplaceable role in global change science. Global change research leads the overall thinking of environmental science, and it has a very significant role to promote the further development of marine environmental geology including marine hazard geology—and marine hazard geology will gradually establish its rightful place in global change science.

3. Object and Content of Study of Marine Hazard Geology

The research objective of marine hazard geology is the correlation between marine geological hazard and human society and its living environment. On the one hand, it is the influence of nature and change of marine geological hazard on human society; on the other hand, it is the impact of human activities on the marine geological hazard. Marine hazard geology mainly researches the formation conditions and genetic mechanism of marine geologic hazards, and researches laws of development and hazard processes of all kinds of marine geology hazards, and provides a scientific basis for hazard assessment, monitoring, forecast and prevention, and control of marine geological hazards. The main research areas are described in the next subsections.

3.1. Types of Marine Geological Hazards

Classification of marine geological hazard is one important basic theoretical problem of marine hazard geology, and it is also an important research area. According to different classification principles, it has different classification schemes; a scientific geological hazard classification system with practicability, hierarchy, and correlation must be established for the in-depth investigation and study of marine geological hazard; and it can deeply reflect the differences and or internal connections between all kinds of geological hazards. Different regions have different combination types of geological hazards. On the contrary, the combination of different types of geological hazards tends to reflect the development characteristics of geological hazards in different regions.

3.2. Formation Conditions and Genetic Mechanism of Marine Geological Hazards

Marine geological hazard has its certain geography, topography, and geological background, and it usually only occurs under particular inducing factors. The formation mechanisms of all kinds of marine geological hazards are complex and varied, and the hazard factors can be different natural factors, human factors, and can also be the integrated effects of natural and human factors. The formation conditions and genetic mechanism of marine geological hazards is the primary research content of marine hazard geology.

3.3. Developmental Laws and Hazard Developing Process of Marine Geological Hazards

There are dozens of types of marine geological hazard. The formation of geological hazards must have the hazard-caused body and the hazard-bearing body, and the combination of the two determines the hazard degree. The distribution, occurrence, development, and the developing process of all kinds of marine geological hazard are very different, so the investigation and master of the development law and developing process of marine geological hazard are crucial for the prediction and prevention of hazard; this is an important research area of marine hazard geology.

3.4. Zoning of Marine Hazard Geology and Risk Evaluation of Marine Geological Hazards

Study on the zoning of marine hazard geology is the basis for regional marine geological hazard evaluation, and it is also the important scientific basis for marine geological hazard prediction and prevention; it is one of the main research areas of marine hazard geology. Study on zoning and risk assessment should include the zoning basis, risk evaluation principles, evaluation index, evaluation method, and regionalization scheme.

3.5. Hazard Assessment of Marine Geological Hazard

Hazard evaluation is an important part of marine geological hazard prevention and reduction. Hazard assessment is to assess the risk of geological hazard and the caused damage, the ability to resist hazards of human society in the existing economic and technical conditions, and evaluate the economic input for the hazard prevention and reduction and the possibility to obtain economic benefit and social benefit. Its content includes risk assessment, vulnerability assessment, destruction loss assessment, and prevention and reduction engineering as four aspects, of which the hazard evaluation and vulnerability assessment are the basis of hazard assessment, destruction loss evaluation is the core of hazard evaluation, and prevention and control engineering evaluation is the practical application of hazard evaluation.

3.6. Monitoring, Prediction, and Prevention of Marine Geological Hazard

Marine geological hazard monitoring aims to understand and grasp the occurrence and evolution regularities of hazards, timely predict the occurrence and the development trend of hazards in order to avoid or reduce the loss of hazards. Monitoring includes hazard condition monitoring, hazard process monitoring, and feedback monitoring of hazard prevention benefit; marine geological hazard forecast is the basis of hazard prevention decision-making, the establishment of a prediction model also takes account of the geological factors, human activities and social and economic factors; the fundamental goal of marine geological hazard prevention and reduction is to achieve the best effect. The basic way to control is to first control hazard resources, eliminate or weaken the activity energy of hazard-caused body, and reduce hazard threat; secondly, take preventive or avoidance measures for the hazard-bearing body to protect against the hazard, or increase resistance of the affected to the hazard.

The objective of the marine hazard geology study is the scientific evaluation, reliable prediction, effective prevention measures on the marine geological hazard; and hazard assessment and monitoring, prediction, and prevention of hazard is the key link of hazard prevention and reduction, and is an important research area of marine hazard geology.

Marine hazard geology is an important branch of marine geology, and also it is an important part of environmental geology, so it is the cross-science of geological science, marine science, environmental science; and hazard science; this scientific development will continue to promote the development of this subject. Marine hazard geology in China mainly researches the hazard geology of estuary, coastal, and offshore areas in China, and it has the dual nature of marine hazard geology and specialized hazard geology.

4. History Review and Main Progress of Study on Marine Geological Hazards

4.1. Historical Review

China is a country with an ancient civilization with a history greater than 5000  years, and it is also a natural disaster–prone country. There are numerous historical documents from the very early beginnings of the country that have observed and recorded disaster phenomena. In the ancient records, most reports of disaster are related to earthquake disaster, drought and flood disaster, collapse, landslide, debris flow, ground cracks, and other geological hazards. As early as 2000  years ago, volume nine of the Han recorded that in the second year of Chuyuan of Emperor Yuan of Han (47  BC) in June…In this year the earth moves again, and Beihai water overflow killing people; this is our country's earliest known records about the marine seismic, and it can be used for speculation of the occurred offshore earthquake and earthquake tsunami hazard. The rich ancient calamity phenomenon observation records provide us with valuable basic data for the study on hazard space-time distribution rule, hazard assessment, and hazard history.

The study of marine geological hazard is closely related to the development and construction of coastal countries for the coastal areas, especially the exploration and exploitation of offshore oil and gas resources (so far for more than half a century).

The study of inshore shelf geological hazard of countries all over the world began with marine oil and gas resources exploration, mining, and construction activities. Offshore oil and gas development has experienced a development process that is from coastal, shallow sea to deep sea. From 1897 to the beginning of the 1940s was the initial stage of marine petroleum development, and the main engineering facilities were wood structure platforms and the artificial island, and they could only explore oil in the offshore with depth of less than 10  m; there was not enough attention paid to the marine geological hazard.

In 1947 America built a steel structure fixed platform in the Gulf of Mexico, and the research of geological hazard at that time was mainly carried out for the drilling platform hazard and was performed around the drilling platform within a small range. Within more than 20  years from the end of World War II to the end of the 1960s, the rapid development of mobile offshore drilling units promoted offshore oil exploration to the continental shelf; the operating water depth was more than 200  m. At the end of the 1970s and 1980s, with the development of platforms and drilling technology, marine oil and gas exploration and development water range was further expanded to water depth more than 500  m, and the North Sea and the Gulf of Mexico continental shelf deep-water oil and gas resources were successfully developed. In this period, marine geological hazard study was extended to the continental shelf area, and combined with the regional engineering geological investigation; significant progress was made on the analysis of seabed soil slip and sand liquefaction evaluation.

In the 1990s, technical problems of drilling, oil production, gathering and transportation, and storage for temperate offshore oil and gas mining were successfully resolved, and offshore platform and the pipeline technical problems in the high latitude regions also made a major breakthrough; marine oil and gas exploration and development has made great progress, operation depth has been constantly refreshed, achieving 3000  m in 2002. Globally nearly 100 deep-water oil and gas fields have been discovered, and the scope of operations has been expanded from the North Sea, the Gulf of Mexico and other traditional areas to West African, South American, and Australian continental shelf waters. In this period, the investigation and study of marine geological hazard also extended to the continental slope waters with depths greater than 500  m; slope soil instability and gas hydrate and other geological hazard factors have become the focus of research.

Offshore oil and gas development in China has experienced two stages of development. The first stage was 1965–1981, when China started the continental shelf oil and gas exploration, finding six oil fields in the Bohai Sea, South Yellow Sea, East China Sea, North Gulf of the South China Sea, Yingge Sea, and Pearl River Estuary (testing was in the Bohai Sea). The second phase, which started in 1982, is the cooperative development stage. From 1982, Chinese CNOOC invited bids for South China Sea, Bohai Sea, South Yellow Sea, and East China Sea oil and gas blocks. From 1983, we began the continental shelf oil and gas exploration and development of Sino foreign cooperation or self-operation, and the marine oil and gas field construction, and put into operation one after another. At present, China has the independent ability of oil and gas exploration and development in shallow waters with a depth of 500  m.

The domestic investigation and research of marine geological hazard was developed in the early 1980s along with large-scale exploration and exploitation of offshore oil and gas. At that time, every major oil company carried out the regional engineering geology survey of oil and gas areas, and platform and pipeline engineering site investigation. In 1983, South China Sea West Oil Company and the Institute of Oceanography, Chinese Academy of Sciences, and other units took the lead in the engineering geological survey of 11-1 sea area platform site of Beibu Gulf. Then, South China Sea West Oil Company and the Institute of Oceanography, Chinese Academy of Sciences, and other units performed regional geological hazard survey of 20  ×  40  km network in Beibu Gulf and the northwestern area of South China Sea shelf, and the hazard geological survey of platform and pipeline area for 11-4 sea area and 10-3 sea area. In 1985, Shanghai Marine Geological Survey Bureau performed regional engineering geological survey of 1:200,000 in the continental shelf of the East China Sea oil and gas exploration area. Between 1986 and 1987, the Institute of Oceanography, Chinese Academy of Sciences, and the Mechanical Research Institute of Chinese Academy of Sciences, according to the requirements of Yellow Sea Oil Company, conducted a regional survey project on the shallow water west of South Yellow Sea 123°E and outer edge of the shallow water of North of Jiangsu. From 1986 to 1990, the Second Marine Geological Survey Brigade of Ministry of Geology and Mineral with the United Nations Development Program Funding conducted 1:200,000 marine geological surveys in the Pearl River Mouth Basin of South China Sea, and completed a total of nine international standard maps (Feng et al., 1996). The aforementioned surveys all focus on geological hazards.

China's attention to the coastal geological hazard started with coastal city construction, coastal development, and coastal engineering activities. Since the end of 1950s, studies have been conducted for coastal erosion, ground subsidence, sea surface subsidence, seawater intrusion, and degradation of coastal wetlands, harbor siltation, and other geological hazards, and significant progress has been made. Especially from 1985 to 1990, the Institute of Estuarine and Coastal Zone of Qingdao Ocean University has carried out Sediment Dynamics Research in Central and Southern Bohai Sea and Yellow River Estuary cooperating with the United States and Canada; and a large project of National Natural Science Foundation: China Main Estuaries Sedimentary Dynamic Processes and Its Application thoroughly researched the subaqueous slope instability of the Yellow River estuary, analyzing and discussing the subaqueous collapse, landslide, and sediment gravity flow block movement of the Yellow River Delta, revealing a detailed picture of Yellow River estuary sediment dynamic processes and the hazard geology factors of the estuary area (Yang and Shen, 1991).

Since the 1990s, the international community and governments have paid great attention to the global environmental problems. China's government's positive responses to the international community, under the promotion of the United Nations International Disaster Reduction in Ten Years, put disaster reduction into the national economic and social development planning. From then on, the investigation and study of marine geological hazard and hazard prevention and reduction work has entered a new stage, and in the past 20  years, we have made a series of important progressive steps.

In July 1991, the first China marine geological hazard prevention symposium was held in Qingdao, and a China marine geological hazard professional committee was established; this is a mark showing that China has paid more attention to marine hazard geology.

In 1992, the Chinese Disaster Defense Association held the Hazard Prevention and Reduction and Development of Coastal Regions of the Country Seminar in Yantai; this meeting played an important role for further research work to promote the coastal zone hazard geology.

In 1996, based on present national geologic hazard investigation, the Atlas of Provincial Geological Hazards of China edited by Duan Yonghou was published (Chinese Hydrogeological Engineering Geological Prospecting Institute, 1996). The Atlas proposed the classification, regional distribution, damage degree, and development trends of the main types of geological hazards in China. It put sea level rise, seawater intrusion, coastal erosion, harbor siltation, storm surge into the ocean (coastal) dynamic hazard, into the mapping range (Duan, 1997).

In 1996, Li Shaoquan first proposed the phrase coastal zone geological hazard, and discussed five basic attributes of coastal zone geological hazard and classification principle of coastal zone geological hazard (Li, 1996a,b). Ye Yincan first discussed the formation mechanism and morphology characteristics of submarine landslides in island sea areas, and conducted quantitative analysis of the slope stability by the joint action of wave and gravity and the sand liquefaction caused by wave bottom pressure (Ye et al., 1996). Geological Hazards of Southern China Coast explains the geological hazard type and development regularity of the coastal areas of Southern China, and puts forward the fuzzy comprehensive evaluation method of geological hazard and system analysis method of geological hazard prevention (Zhan et al., 1996). China Offshore Geology has a chapter China Offshore Environmental Geology and Hazard Geology to discuss the basic characteristics of various geological hazards and the stability of offshore environmental geology in China, and puts forward the zoning of geological hazard and geological hazard prevention countermeasures (Xu et al., 1997).

Guangdong Coastal Geological Environment and Geological Hazard published in 2003 specialized in the regional hazard geology. This book has rich data and diagrams and explains Guangdong coastal geological hazard type and space-time distribution, comprehensive assessment of geological environmental quality and zoning, development trend of coastal geological hazards and forecasting index system, and also introduces the geological hazard database and geographic information system, with the management of geological environment and geological hazard prevention measures (Xie et al., 2003).

From 1997 to 2001, the State Oceanic Administration organized the implementation of the China's exclusive economic zone and continental shelf survey as major national project, including hazard geological environment survey and evaluation. The measured area includes the oil and gas resources (development) district outside of the Pearl River mouth basin continental shelf of the northern South China Sea, such as South Yellow Sea oil and gas resources prospective area and the oil and gas resources (development) district in the basin of the East China Sea, Beibu Gulf, Yingge Sea, and southeastern Hainan. At the same time, geological hazard investigation and comprehensive evaluation were conducted for the Yellow Sea, East China Sea, and South China Sea and their coastal zones and surrounding waters; developed the 1:200,000 scale Yellow and East China Seas and South China Sea hazard geology map, and 1:100,000 scale oil and gas resources development zone's seabed hazard geology map (Li et al., 2003; Du et al., 2004), and classification of coast zone hazard geology factors and zoning of China coastal zone hazard geology. On this basis, the report China Offshore Waters and Adjacent Sea Marine Environment was compiled, with a chapter Hazard Geology Environment, which describes the type and distribution characteristics of geological hazards and puts forward the hazard geology zoning and comprehensive evaluation method of seafloor stability (Guo et al., 2004).

With the support of the National Natural Science Foundation, Ye Yincan, Zhuang Zhenye, and others, based on the related research results, conducted in-depth research on the Yangtze banks sand wave bedform characteristic parameters, distribution and direction of motion, using the hydraulic calculation method to obtain the migration rate and motion magnitude of sand wave. According to the stability sign, they divided the continental shelf sand wave into four grades, namely moving sand dune, weak moving sand dune, stable residual sand dune, and demising dune; this division still is the primary one in academic circles (Ye et al., 2004b; Long et al., 2007; Zhuang et al., 2008).

China Coastal Zone Hazard Geology Characteristics and Evaluation published in 2007 (Li et al., 2007b) systematically summarizes the past research achievements of geological hazards of coastal zone in China, and puts forward the classification scheme of hazard geology factors and geological hazards, details the coastal zone hazard geology mapping, risk assessment, and the division method, and lists the typical cases of the coastal zone hazard geology research in China.

China's deep-water oil and gas resources are mainly in the 300- to 3000-m-deep waters of the South China Sea. China National Offshore Oil Corporation in cooperation with the Haski Energy Company, in June 2006 discovered Liwan 3-1 gas field in the Pearl River Mouth Basin deep-water block 29/26, and in February 2009 completed the first evaluation well Liwan 3-1-2 drilling of this block, thus becoming China's first deep-water gas field by drilling so far; this marked the start of China's deep-water oil gas exploration and development. In the investigation of the site selection and management of routing and platform, China's engineering investigation unit cooperated with FUGRO N.V. to conduct investigation and research on the stability of soil slope at the depth of about 600–1500  m, which opened a prelude to the deep-water hazard geology research in China.

Comprehensive investigation and evaluation of China offshore sea (908 special plan) approved to be established by the State Council in September 2003 was a new milestone in marine investigation in China. This special plan was conducted from 2004 to 2012. The scope of the investigation was the internal waters, territorial sea, and part of the sea area outside of territorial sea; the survey area was about 676,000  square kilometers, of which the internal water area is 297,000  square kilometers, territorial sea is about 84,000  square kilometers, and part sea area outside of territorial sea is about 295,000  square kilometers. The main investigation area was selected for large deltas, bays, sea areas adjacent to intensive city, and important coastal ecological region. Marine hazard survey was the important content of this special project, including typhoon, storm surge, billow, tsunamis, sea ice hazard and other marine environment hazard investigation, coastal erosion, seawater intrusion, soil stalinization, wetland degradation and submarine landslide, active fault, earthquake, ancient river channel sand body, shallow gas, liquefaction of sand soil and soft formation and other marine geology hazard survey, red tide disaster, species invasion, propagation of marine aquaculture pathogen biology, and other marine biology hazard investigation. Results of this project will greatly enrich the practice and theory of the marine hazard geology survey in China, and make an important contribution to the development of marine hazard geology.

4.2. Main Research Progress

4.2.1. Classification of Marine Hazard Geology Factors and Marine Geological Hazards

Study of marine hazard geology factor is a basic theoretical problem of marine hazard geology, and it has 40  years of history. As early as 1980, G. B. Carpenter, according to the risk on the engineering, divided all kinds of hazard geology factors of continental shelf into hazardous geology factor and constraint geology factor as two categories. Since the 1980s, a variety of classification schemes have been proposed by scholars. The representative schemes in China are: the earth sphere classification according to geological hazard power (Liu et al., 1992), classification of dynamic generation causing geological hazards (Chen and Li, 1993), and classification according to the genesis in combination with the engineering risk (Li and Yu, 1994).

Classification of marine geological hazards to the most common scheme is the genetic classification. In addition, there are other classification methods that are based on the marine geographic unit, spatial distribution, hazard chronology, and so forth.

China Coastal Zone Hazard Geological Characteristics and Evaluation combines the characteristics of China's coastal zone hazard geology factors to propose a coastal zone hazard geology factor classification system, and at the same time puts forward the classification and grading scheme of coastal zone geological hazards (Li et al., 2007b).

At present, the comprehensive classification method based on genesis has been accepted by most researchers, and has been widely cited. In addition, the long-term existing confusion of hazard geology factor classification and geological hazard classification has more and more consistent understanding in recent years; researchers think the difference between the two is that the geological hazard classification is the attribute to divide the properties of hazard and the measure of hazard degree, and hazard geology factor classification is the properties of geological factors that might bring hazards and the features that induce hazards.

4.2.2. Studies of Gradually Varied Marine Geological Hazards

Gradually varied marine geological hazard has features of slow occurrence and gradual development, such as coastal erosion, sea level rise, land subsidence, seawater intrusion, degradation of coastal wetlands, and harbor siltation. These kinds of marine geological hazards occur mainly in the coastal areas, and generally speaking the harm scope is broad, the harm degree aggravates gradually, and the consequences and