【作者】 郭婷婷；

【导师】 徐锡伟；

【作者基本信息】 中国地震局地质研究所 ， 构造地质学， 2013， 博士

【摘要】 2008年5月12日中国汶川发生里氏8.0级特大地震，沿地表可见活动断层无坚不摧的地震地表破裂与强烈的地震动使得地表破裂带沿线及其两侧近断层的建筑物遭受了毁灭性的破坏，同时，地震引发的大量山体滑坡、岩石崩塌、泥石流等次生地质灾害，加重了建筑物破坏程度与人员伤亡。大量震害实例分析表明，活动断层的突发性错动是产生地震的主要根源，且活动断层沿线是建筑物破坏与人员伤亡最为严重的区域。究其原因，主要是活动断层同震地表破裂、错动、强地震动及其引发的次生地质灾害造成的建筑物倒塌、毁坏所导致。活动断层是产生地震的主要根源，但是目前我们的地震预报工作尚未能科学地解决，故我们需依据建筑物的抗震设防要求，分析汶川地震建筑物的破坏原因，以便提高建筑物的抗震设防能力。地震通常会在震中区形成强烈的地面振动使得其上建筑物遭受破坏，地表破裂型地震常常能够沿地表可见活动断层两盘岩体产生错动直接毁坏跨越断层的地面建构筑物，即地震的破坏可概括为强地震动效应和强震地面破裂效应两种类型。因此，一方面，从建筑物破坏分析中总结原因，提高与加强抗震措施，依据现行建筑抗震设计规范，确保建筑物的抗震性能，以备应对强地震动效应达到有效减轻地震灾害；另一方面，我们旨在全国活动断层探测准确位置的工作基础上，合理地确定避让宽度，主动避开“具有发震能力的活动断层”来减轻可能遭遇的地震灾害。本文将结合汶川地震震后大量建筑物震害特征，以及同震地表破裂带宽度与建筑物破坏程度之间的定量关系，通过汶川地震大量的实地地表破裂变形测量数据，以及收集到的逆断层型历史地震地表破裂带宽度资料，采用统计分析方法，初步确定活动逆断层“避让带”的宽度范围，为地面建筑物“避让”活动断层提供科学依据。本文采用野外震害实地测量和调查、室内资料统计与数据计算分析相结合的技术方法，讨论建筑物破坏情况与防震措施；分析同震地表破裂带宽度与建筑物破坏特征之间的定量关系；采用统计分析方法初步确定活动逆断层“避让带”的宽度范围。主要得到以下结论：1.通过震害实例分析表明，活动断层的突发性错动是产生地震的主要根源，且活动断层沿线是建筑物破坏与人员伤亡最为严重的区域。活动断层“避让”是必须的，也是可行的。只要避开活动断层一段距离，建筑物破坏程度就很大程度上减轻。从而可有效地减轻人员伤亡与经济损失。2.中强地震、大地震或特大地震等可在地表产生大量地震地表破裂，其表现形式是各种各样的，不管其结构复杂程度、破裂长短，其带来的强烈地震动与地表破裂、错动或变形，均会不同程度地影响地面及其地表建筑物，并引起地面建筑物的破损甚至倒塌。同时，强烈的地震动与地表破裂还可诱发山体滑坡、崩塌、泥石流等次生地质灾害，造成建筑物毁坏与人员的伤亡、掩埋。3.通过对川西地震灾区的几种主要结构类型建筑物的破坏特征进行调查，分析讨论了建筑物的震害情况，可得到所考察川西地区城镇不同结构类型建筑物的破坏程度由小到大依次为：钢筋混凝土框架结构、砖混结构、木结构、砖木结构。建议未来多采用框架结构与具有抗震措施的砖混结构。4.根据现行建筑物的抗震设防要求与建筑抗震设计规范，从建筑物选址、建筑抗震设计及建筑施工等各个环节，对汶川地震灾害中的典型建筑物破坏案例进行了破坏原因分析与讨论，得出：①建筑物的选址一定要避开活动断裂带，须根据当地实际地质情况，合理确定“避让带”宽度；同时，也要避开地质灾害危险地段。②抗震结构体系的选取应考虑：使结构体系具有多道抗震防线；尽量避免刚度不连续结构体系；确保各构件之间的连接等问题。③隔震和消能减震设计以及抗震新型建筑材料的广泛应用将从抗震各个环节共同提高建筑物的综合抗震能力。5.通过几处典型观测点同震地表变形量与建筑物破坏关系的定量分析，以及对前山断裂的汉旺-白鹿地表破裂带，中央断裂带的北川-映秀地表破裂带以及NW向小鱼洞地表破裂带多处测点的地表破裂带宽度进行统计的结果初步分析，可以得到：①发震断层的同震地表错动会造成上面建筑物的撕裂，这是任何抗震措施均无法抵挡的。发震断层的同震错动对地表变形与地面建筑物直接毁坏呈局部化特征，其影响宽度是有限的，一般都在30m范围内。距离断层越近，地表破裂越严重，地面建筑物破坏越严重，且断层上盘的地表破裂与建筑物破坏比下盘严重。②从汶川地震中3条地表破裂带上的52处测点的强地表破裂宽度统计结果，可以得到：汶川地震地表破裂带宽度大部分在15-35m之间，个别观测点变形带宽度大于40m，甚至大于100m，这与已有的统计研究结果基本一致。其结果为活动逆断层的“避让”宽度的确定提供了定量判别标准与科学依据。6.综合大量汶川地震地表破裂带宽度与其它逆断层型历史地震地表破裂带宽度数据，采用同震地表破裂带宽度统计法，计算得出活动逆断层“避让带”的有效宽度约为30m。并综合实测断层上、下盘变形带宽度的2:1比值关系以及相关文献数据，初步给出活动断层上盘的“避让”宽度取值约20-22.5m，下盘的“避让”宽度取值约为7.5-10m。其结果与徐锡伟等前人研究结果以及美国加州“地震断层划定法案”规定的活动断层两侧合计30m“避让带”宽度非常吻合，并获得跨断层地质探槽剖面分析法所验证，可为建筑工程避让活动逆断层提供定量分析与参考依据。7.建议相关部门继续加强活动断层“避让带”宽度研究，加强活动断层探测工作，并加强活动断层“避让带”立法与执法管理，以便更好地促进活动断层“避让”工作开展，切实提高我国震害预防的能力。更多还原

【Abstract】 On May12,2008, a great earthquake of Ms8.0occurred in Wenchuan County,Sichuan Province, which produced surface ruptures and buildings damage, and causedmany landslides, bedrock collapses, and other secondary geological disasters, adding tothe extent of earthquake disasters. As shown in the earthquake damage examples,sudden rupture of active faults is the main cause of the earthquake, and areas along theactive faults are the sites with most serious building damage and casualties. The mainreason is that coseismic surface ruptures, dislocation, strong ground motions and theirsecondary geological disasters can spawn building collapse and destruction.It is generally accepted that crustal earthquakes are caused by sudden displacementon active faults, and many quakes of M>6are accompanied by faulting at the earth’ssurface. However, current science and technology do not allow scientists to predictearthquakes accurately through monitoring active faults and/or seismic precursors. So itis necessary to analyze causes of building damage in the Wenchuan earthquake toimprove capacity of seismic protection of buildings. Tectonic earthquakes usuallyproduce strong ground vibration which makes buildings destroyed in the epicenter area,and rock mass movement on either side of the causative fault can make buildings toreand broken Therefore, on the one hand, people should summarize the reasons frombuildings destruction to improve and strengthen anti-seismic measures, and ensureseismic performance of buildings to meet earthquake-proof requirements according toexisting code for seismic design of buildings. On the other hand, people shoulddetermine a reasonable width of avoidance to seismogenic active faults to mitigatepotential earthquake hazards based on the accurate positions of the active fault. Theobjective of this thesis is to study safety distance range of active thrust faults which areexposed to major earthquakes. The work of this thesis includes analysis of buildingdamage in the2008Wenchuan earthquake by using the method of statistical analysis,and the quantitative relation between co-seismic surface rupture width and buildingdamage characteristics, and based on measurement data of surface rupture deformationin the Wenchuan earthquake and the rupture zone width data of historical earthquakes.The results of this work would provide a scientific basis for buildings avoidance fromactive faults.In this theses, through field measurements and investigations of earthquake disasters, statistics of indoor data and calculation and analysis of data，building damage and itsprevention measures are analyzed, the quantitative relationship between the co-seismicsurface rupture zone width and building damage characteristics is discussed，and safetydistance range of thrust faults is primarily determined by using the method of statisticalanalysis. The the main conclusions are as follows:1. Case analysis of earthquake damage shows that sudden rupture of active faults isthe main cause of the earthquake, and areas along the active faults is the place sufferingfrom most serious building damage and casualties. Avoidance of active faults isnecessary and feasible. If buildings can avoid faults for a distance, the extent of damageof buildings will be largely reduced, as to reduce casualties and economic losses.2. Major or great earthquakes can generate a lot of surface ruptures, which havevarious expressions, regardless of theirs structural complexity and fracture length, andbring strong ground motions and surface deformation which will affect the surface andbuildings to different extents, and cause surface buildings damaged and even collapse.At the same time, secondary geological disasters will also cause building devastationand personnel casualties.3. Through investigations to the damage characteristics of main structure types ofbuildings in earthquake-stricken areas of western Sichuan, earthquake damage ofbuildings is discussed, and damage extents of different types of building can bearranged in an ascending order: reinforced concrete frame structure, masonry structure,wooden structure, brick-wood structure. Therefore, it is recommended to adopt framestructure and masonry structure with anti-seismic measures.4. According to the existing seismic protection requirements of building and codes forseismic design of buildings, typical building damage in the Wenchuan earthquakedisaster and its reasons are analyzed and discussed from buildings location, seismicdesign, building construction and other aspects, and corresponding measures aresuggested, which are stated below.①The building site should be away from active faults which are capable ofgenerating major earthquakes. Reasonable width of avoidance of seismogenic activefaults can be determined according to actual geological situation. Meanwhile, the siteswith potential geological hazards should also be avoided.②The anti-seismic structure system should be correctly selected: to make structuresystem several seismic fortification lines; to avoid the structural system ofdiscontinuous stiffness; to ensure connection between the various components of structure.③New technology about seismic isolation and energy dissipation and new buildingmaterials should be vigorously developed and applied to improve comprehensiveaseismic capability of buildings.5. Quantitative relationship between co-seismic surface rupture zone width andbuilding damage characteristics is analyzed， and surface rupture width data ofmeasuring points in the Hanwang-bailu, Beichuan-Yingxiu and Xiaoyudong surfacerupture zones are statistically analyzed, yielding the following conclusions:①Coseismic rupture of seismogenic faults will cause buildings tore and broken,which is overwhelming with any anti-seismic measures. And coseismic rupture ofseismogenic faults can directly destroy the ground and buildings, which are of localizeddeformation characteristics. Its width effect is limited, generally in the range of30m.The closer to faults, more serious surface rupture is, more serious buildings destructionis. Surface rupture and building destruction on the hanging wall of the seismogenicthrust fault is more severe than that on the footwall of the fault.②From the statistical results about surface rupture width at52measuring points in3Wenchuan earthquake rupture zones, some conclusions can be obtained: the width ofthe Wenchuan earthquake surface rupture is mostly between15-35m, deformation bandwidth of individual observation points is greater than40m, even more than100m, whichis basically consistent with existing statistical results. The results provide a quantitativestandard and scientific basis for determining avoidance width to the thrust fault.6. A lot of data of surface rupture zone width of the Wenchuan earthquake and otherwidth data of surface rupture zones of historical earthquakes of thrust faults arecomprehensively analyzed. As effective width of thrust faults,"avoiding belt" iscalculated to be about30m with statistical analysis methods. Avoiding width of thehanging wall of active fault is about20-22.5m, and avoiding width of the foot wall isabout7.5-10m. These results can provide construction’s with avoiding distance fromthrusting faults and others types of faults as references and quantitative standard.7. It is suggested that further attention should be paid to the research on fault’s"avoiding belt" width and the probing of active faults, and “safety distance” from activefaults should be taken as a legal regulation for constructions. So that earthquake hazardscan be positively and effectively reduced.更多还原