| 活断层的定义与分类——历史、现状和进展 |
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| 引用本文：吴中海.2019.活断层的定义与分类——历史、现状和进展[J].地球学报,40(5):661-697. |
| DOI：10.3975/cagsb.2019.051001 |
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| 基金项目:国家自然科学基金项目(编号: 41571013);中国地质调查局地质调查项目(编号: DD20160268; DD20190396) |
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| 中文摘要:活断层是在最近地质时期持续活动, 并且未来仍将活动的断裂。活断层作为破坏性地震的主要危险源及其可能衍生的多种潜在灾害作用, 意味着它的存在对所在区域的城镇发展和重要基础设施建设都存在难以回避的灾害风险问题。而中国是世界上活断层数量多且遭受相关灾害影响特别严重的国家之一, 如何科学评价活断层危险性且有效减轻相关的灾害风险必然是我国经济社会发展中长期面临的重大课题。而活断层定义和分类是评价活断层灾害风险的重要依据。在全面系统地梳理分析国内外在这一领域的历史与现状基础上, 介绍并总结了代表性国家和地区、相关的规范标准以及活断层编图与空间数据库建设工程等所采用的活断层定义和分类方案。综合分析与对比结果表明, 在制定科学合理的活断层定义及分类方案时,必须综合考虑区域的现今构造动力学背景、现有技术手段及地质上的可操作性、应用目的和社会对活断层风险的可接受程度等因素。活断层定义的关键是过去活动时限及潜在发震能力的选择或确定, 前者涉及“新构造、第四纪、晚第四纪、全新世和历史上”共5个不同时间尺度, 后者包括“M≥5.0的破坏性地震、M≥6.0的强震和M≥6.5的可能产生地表位移或变形的地震”共3类。晚第四纪和全新世等短时间尺度的活断层定义适合应用于构造活动强烈的板块边界带, 但第四纪和新构造等长时间尺度的活断层定义在板内变形区和稳定大陆区, 或包含了多种不同活动构造域的区域更为可取。而M≥5.0地震适用于作为区域性防震减灾的震级标准, M≥6.5地震一般可作为活断层避让规范或法规中的标准。国内外最常见的活断层分类方案是基于断裂活动强度与频度(主要通过断层滑动速率与地震复发间隔两个定量参数来体现)和活动时代的分类。但在确定不同级别断层的具体定量参数时, 需要综合考虑区域内主要活断层活动强度和活动时代的差异性与现有数据的多寡及有效性, 从而达到分类方案可有效区分不同级别活动断裂的目的。另外, 活断层评价中还经常涉及活断层的活动性与危险性问题, 前者反映的是断裂过去的活动状态, 主要通过断层的最新活动时间、平均滑动速率和大地震平均复发间隔等定量参数体现, 而断层的危险性主要针对的是活断层在人类社会所关心时段内或工程寿命期内, 断裂活动可能造成的灾害及其风险程度, 需要在判定断裂活动性基础上, 进一步明确未来强震可能出现的位置、震级的大小、地表断层的分布以及一旦发生强震可能造成的地质灾害类型及分布等, 通过合理区分出断层的危险性为政府管理部门和工程规划建设部门有效减轻、防控或管理活断层灾害风险提供更具实用性的依据。目前, 世界上活断层比较发育且灾害影响显著的典型国家和地区都十分重视全国范围内的活断层普查工作, 并把综合编制可更新的且公开共享的全国性活断层图及空间数据库作为长期且重要的基础地质工作, 以及有效应对活断层灾害风险和服务社会的重要方式。其中美国西部地州和新西兰等制定的活断层避让法规或规范, 非常值得活断层数量多且相关灾害问题突出的中国或类似的国家和地区借鉴。 |
| 中文关键词:活断层 新构造 能动构造源 地震复发间隔 地震危险性评价 |
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| The Definition and Classification of Active Faults:History, Current Status and Progress |
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| Abstract:Active fault is generally defined as a fault that is expected to cause sub-surface deformation or destructive earthquakes (M≥5.0 shallow earthquakes) in the future, and is treated as the main hazard source of destructive earthquakes and related potential hazard effects. The presence of active faults means unavoidable disaster risk for urban development and important infrastructure construction along the fault zones. China is one of the countries with a large number of active faults and is particularly affected by related disasters in the world. How to scientifically evaluate the risk of active faults and effectively mitigate the related disaster risks is bound to be a major issue in China's long-term economic and social development. The definition and classification of active faults is an important basis for evaluating the hazard risk of active faults. Based on a comprehensive analysis of the history, status and progress of the definition and classification of active faults, this paper summarizes the definition and classification schemes of active faults used in representative countries and regions as well as in some relevant standards, active fault mapping, construction of spatial database and some other fields. The comprehensive comparison results show that the reasonable adopting of definition and classification of active faults must take into account the current tectonic dynamic background, existing technical means and geological operability, application purpose and social acceptability of active faults risk in a specific area. The key parameters are the past activity time limit and the potential seismogenic ability in definition of active faults. The former usually involves five different time scales, i.e., Neotectonic, Quaternary, Late Q0uaternary, Holocene and historical process, whereas the latter generally includes three classes, namely, M≥5.0 destructive earthquakes, M≥6.0 strong earthquake and M≥6.5 which may produce the surface displacement or deformation. The definition of active faults using short time scale, such as late Quaternary and Holocene, is usually suitable for the plate boundary zone where tectonic activity is strong, but it is preferable that active faults are defined as long time scale of Quaternary and neotectonics in the intraplate deformation region and stable continental region, or a large region that contains many different active tectonic domains. The magnitude standard of M≥5.0 earthquakes is generally applicable to regional earthquake prevention and disaster reduction in many countries or regions, but the M≥6.5 earthquakes generally is used as the standard in the rules or regulations of active fault avoidance.The most common active fault classification schemes in many countries or regions are based on the degree or frequency of activities of fault, which mainly are reflected by the two quantitative parameters of fault slip rate and earthquake recurrence interval as well as by activity epochs. However, when determining the specific quantitative parameters of different active levels of faults, it is necessary to comprehensively consider the differences of activity degrees and epochs of faults in the study region as well as the amount and validity of existing data so as to achieve the purpose of classifying different active levels of faults effectively. In addition, the degree of activity and hazard of active faults are often involved in the risk assessment of the active fault. The former reflects the fault activity state in the past, and involves some quantitative parameters including the latest activity time, the average slip rate and the earthquake recurrence interval of active faults. The potential risk of active fault is aimed at the disaster that the active faulting may cause and its degree of risk in the coming period that the human society is concerned with or in the project life period. The risk needs to be evaluated on the basis of determining the degree of activity of faults; the position, size of the magnitude, the distribution of the surface rupture or deformation zone of the future strong earthquake, and the types and distribution of geological hazards that may be caused by the strong earthquake should be further clarified. Therefore, the reasonable distinguishing of the risk degree of active faults is a more practical basis for effective reduction, control or management of active fault disaster risk by government management and construction departments of the infrastructure construction project. At present, many typical countries and regions affected by the active faulting and related hazards have attached great importance to the planned and nationwide active fault surveying, and the comprehensive compilation of updated and publicly shared national active fault maps and spatial databases have been generally considered as important basic geological work and effective measures to cope with the long-term active fault disaster risk as well as the most important way to serve the social security. The authors hold that the active fault avoidance regulations made by the western continental states of the United States and New Zealand are worthy of reference by China or similar countries or regions which have a large number of active faults and prominent related disaster problems with the purpose of effective mitigation of the risk of active faulting in urban planning and important infrastructure construction. |
| keywords:active fault neotectonics capable tectonic source earthquake recurrence interval seismic hazard assessment |
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