Correlations between structural damage and ground motion parameters during the Ms8.0 Wenchuan Earthquake

The Wenchuan Earthquake with a magnitude of Ms 8.0 struck the Sichuan province of China on May 12, 2008, where it mainly affected the area along the Longmenshan fault. In total, 420 three-component acceleration records were obtained by the China Strong Motion Networks Centre during this seismic event, among which over 50 records exceeded 100 gal. In the present study, we collected 48 near-fault acceleration records to derive strong ground motion parameters in terms of the peak ground acceleration, peak ground velocity, peak spectrum acceleration (5% of the damping ratio) and spectrum intensity (5% of damping ratio). We determined the building collapse ratios (CRs) for 20 targeted districts based on data acquired from both the China Earthquake Administration and the Chinese Academy of Sciences, where the CRs combined the data for all building types. Fragility curves were established between the CRs and the corresponding ground motion parameters, based on which the damage criteria were proposed. In particular, we derived the fragility curves for brick-concrete structures and frame-structures. These curves indicate how different structural types can determine the damage sustained. In addition, we developed a method for estimating building damage classifications. If we assume that buildings are built according to the improved Seismic Fortification Criterion in the revised “Code for Seismic Design of Buildings”, the predicted CRs for the 20 targeted districts would be significantly lower compared with the actual damage they sustained, which illustrates the validity of both the method and the revised code.     

四川青川县乔庄镇城区活动断裂探测与评价

青川县乔庄镇主城区坐落于乔庄河Ⅰ级河流阶地面上,平武-青川断裂分为3支呈隐伏状穿过主城区,地表未见明显的断裂新活动形迹。2008年5月12日发生的汶川MS8.0级地震,对青川县乔庄镇造成了比较严重的破坏,出现了沿平武-青川主干断裂通过位置震害显著加重的条带状异常现象,但未见明显的地表破裂。本文在地面地质调查、浅层地球物理勘探和探槽开挖验证结果的基础上,对平武-青川断裂在乔庄镇主城区的通过位置进行了重新定位,定位结果与前人研究结果存在一定的差异。结合地表调查发现的零星地表破裂和探槽下部砂砾石层出现的小尺度变形及位错现象分析,乔庄镇条带状震害加重异常现象应是平武-青川断裂在汶川地震时发生的近地表错动所致。由此联系到汶川地震的余震条带与平武-青川断裂乔庄以东段基本重合的事实,平武-青川断裂的活动性应是下一步研究工作的方向。     

Validation of the SCEC Broadband Platform simulations for tall building risk assessments considering spectral shape and duration of the ground motion

Earthquake simulation technologies are advancing to the stage of enabling realistic simulations of past earthquakes as well as characterizations of more extreme events, thus holding promise of yielding novel insights and data for earthquake engineering. With the goal of developing confidence in the engineering applications of simulated ground motions, this paper focuses on validation of simulations for response history analysis through comparative assessments of building performance obtained using sets of recorded and simulated motions. Simulated ground motions of past earthquakes, obtained through a larger validation study of the Southern California Earthquake Center Broadband Platform, are used for the case study. Two tall buildings, a 20‐story concrete frame and a 42‐story concrete core wall building, are analyzed under comparable sets of simulated and recorded motions at increasing levels of ground motion intensity, up to structural collapse, to check for statistically significant differences between the responses to simulated and recorded motions. Spectral shape and significant duration are explicitly considered when selecting ground motions. Considered demands include story drift ratios, floor accelerations, and collapse response. These comparisons not only yield similar results in most cases but also reveal instances where certain simulated ground motions can result in biased responses. The source of bias is traced to differences in correlations of spectral values in some of the stochastic ground motion simulations. When the differences in correlations are removed, simulated and recorded motions yield comparable results. This study highlights the utility of physics‐based simulations, and particularly the Southern California Earthquake Center Broadband Platform as a useful tool for engineering applications.     

2013年7月22日甘肃岷县-漳县M_S6.6地震震源破裂过程

2013年7月22日,在甘肃岷县漳县交界处发生MS6.6地震,地震震中位置靠近临潭—宕昌断裂.本文通过构建有限断层模型,利用国家强震动台网中心提供的12条强地面运动三分量资料,通过波形反演方法来研究这次地震的震源破裂过程.结果显示这次地震是发生在甘东南地区岷县—宕昌断裂带东段附近的一次MW6.1级逆冲兼具左旋走滑破裂事件,最大滑动量约为80cm.发震断层走向及滑动性质与岷县—宕昌断裂吻合,推断本次地震与东昆仑断裂向北的扩展和推挤密切相关,是岷县—宕昌断裂进一步活动的结果.     

龙头山集镇局部场地地震动效应分析

依据龙头山集镇6个典型场地上的钻探资料及土体的动力非线性特性试验数据,分别建立了相应场地的地震反应分析模型。以幅值折半的龙头山镇强震动台站（053LLT）东西向主震加速度记录作为入射地震动,采用一维土层地震反应分析等效线性化方法计算了场地地震反应,讨论了近地表覆盖土层结构对地震动加速度峰值及反应谱的影响,并对场地效应与震害的关系进行了分析。      

渭河盆地带地貌结构与新构造运动

根据基岩断块山地、波状黄土源（洪积台地），平缓黄土塬（洪积扇裙），阶地等较多实际资料，研究渭河盆地带地貌结构与活动断裂及新构造运动间的关系。研究认为，层状地貌的发育与形成，主要受以盆地带南缘断裂带为主的相关阶状正断层正倾滑活动的控制，盆地带南缘断裂带除产生强烈的垂直差异运动外，还由盆边向盆内扩展，并导致盆地带另一侧向北扩张，此活动格局控制和影响了盆地带地貌的形成与演化，地貌类型及其分布格局可作为研究活动构造及评估地震危险性的标志。     

华山山前断裂中段晚第四纪活动的地貌表现及响应

调查了华山山前断裂中段（石堤峪-杜峪）晚更新世以来,尤其是全新世以来的断层构造地貌,讨论了它们的成因、特点及对断裂活动的响应关系。断层构造地貌主要包括：断层三角面、断层陡坎、洪积阶地、埋藏型洪积扇以及冲沟裂点。对各大沟峪峪口的洪积阶地进行了大比例尺微地貌测量,并在部分沟峪两侧沿断层崖陡坎及冲沟沟床布置了测线。结合T1、T2级洪积阶地位错测量结果及其14C年龄计算得到,华山山前断裂中段6000a-2000aB.P.的垂直滑动速率为1.485mm/a;2000aB.P.以来的垂直滑动速率为3.73mm/a。最后结合野外调查与理论认识,建立了正断层作用下洪积阶地与埋藏型洪积扇的演化模式。本研究结果支持华山山前断裂是1556年华县814级地震发震构造的观点。     

永胜6.0级地震的地质构造背景及发震构造

阐述了永胜Ms6．0级地震震区的地震地质构造背景与构造应力场，结合本次地震的裂度分布几何形态、震源机制解、主余震震中分布和地表破坏等资料，讨论了地震的发震构造，认为程海断裂宾川－金沙江段是该地震的发震断理解。程海断裂宾川－金沙江段以左旋走滑活动为主，兼具正断层性质。     

汶川Ms 8.0地震发震断裂大地震原地重复现象初析

在历史记录中,成都和龙门山地区没有发生过类似汶川MS8.0地震强度的地震。那么,在地质记录中是否会存在类似震级的古地震遗迹?作者分别在中央和前山断裂中段的地表破裂带上4个地点开挖了探槽4个和剖面1个,并进行了断错地貌面的实测。文中从几个地点新老地貌面累计变形量、探槽揭露的古地震遗迹等方面讨论汶川地震发震断裂大地震原地重复现象存在的基本事实。结果表明:无论在中央断裂的小鱼洞、擂鼓镇还是前山断裂的白鹿镇、汉旺等地,汶川5.12地震之后Ⅱ级阶地断层陡坎与Ⅰ级阶地陡坎高度基本呈倍数关系,探槽揭露Ⅱ级阶地标志地层(黄砂土层)在断裂两盘的位差也是5.12地震的约2倍,显示在龙门山地区区域Ⅱ级阶地形成之后,汶川5.12地震发生之前,存在一次与汶川MS8.0地震地表变形规模相当的地震事件     

History of Modern Earthquake Hazard Mapping and Assessment in California Using a Deterministic or Scenario Approach

Modern earthquake ground motion hazard mapping in California began following the 1971 San Fernando earthquake in the Los Angeles metropolitan area of southern California. Earthquake hazard assessment followed a traditional approach, later called Deterministic Seismic Hazard Analysis (DSHA) in order to distinguish it from the newer Probabilistic Seismic Hazard Analysis (PSHA). In DSHA, seismic hazard in the event of the Maximum Credible Earthquake (MCE) magnitude from each of the known seismogenic faults within and near the state are assessed. The likely occurrence of the MCE has been assumed qualitatively by using late Quaternary and younger faults that are presumed to be seismogenic, but not when or within what time intervals MCE may occur. MCE is the largest or upper-bound potential earthquake in moment magnitude, and it supersedes and automatically considers all other possible earthquakes on that fault. That moment magnitude is used for estimating ground motions by applying it to empirical attenuation relationships, and for calculating ground motions as in neo-DSHA (Zuccolo et al., 2008). The first deterministic California earthquake hazard map was published in 1974 by the California Division of Mines and Geology (CDMG) which has been called the California Geological Survey (CGS) since 2002, using the best available fault information and ground motion attenuation relationships at that time. The California Department of Transportation (Caltrans) later assumed responsibility for printing the refined and updated peak acceleration contour maps which were heavily utilized by geologists, seismologists, and engineers for many years. Some engineers involved in the siting process of large important projects, for example, dams and nuclear power plants, continued to challenge the map(s). The second edition map was completed in 1985 incorporating more faults, improving MCE??s estimation method, and using new ground motion attenuation relationships from the latest published results at that time. CDMG eventually published the second edition map in 1992 following the Governor??s Board of Inquiry on the 1989 Loma Prieta earthquake and at the demand of Caltrans. The third edition map was published by Caltrans in 1996 utilizing GIS technology to manage data that includes a simplified three-dimension geometry of faults and to facilitate efficient corrections and revisions of data and the map. The spatial relationship of fault hazards with highways, bridges or any other attribute can be efficiently managed and analyzed now in GIS at Caltrans. There has been great confidence in using DSHA in bridge engineering and other applications in California, and it can be confidently applied in any other earthquake-prone region. Earthquake hazards defined by DSHA are: (1) transparent and stable with robust MCE moment magnitudes; (2) flexible in their application to design considerations; (3) can easily incorporate advances in ground motion simulations; and (4) economical. DSHA and neo-DSHA have the same approach and applicability. The accuracy of DSHA has proven to be quite reasonable for practical applications within engineering design and always done with professional judgment. In the final analysis, DSHA is a reality-check for public safety and PSHA results. Although PSHA has been acclaimed as a better approach for seismic hazard assessment, it is DSHA, not PSHA, that has actually been used in seismic hazard assessment for building and bridge engineering, particularly in California.     

Istanbul Earthquake Rapid Response System: Methods and practices

Potential impact of large earthquakes on urban societies can be reduced by timely and correct action after a disastrous earthquake. Modern technology permits measurements of strong ground shaking in near real-time for urban areas exposed to earthquake risk. The Istanbul Earthquake Rapid Response System equipped with 100 instruments and two data processing centers aims at the near real time estimation of earthquake damages using most recently developed methodologies and up-to-date structural and demographic inventories of Istanbul city. The methodology developed for near real time estimation of losses after a major earthquake consists of the following general steps: (1) rapid estimation of the ground motion distribution using the strong ground motion data gathered from the instruments; (2) improvement of the ground motion estimations as earthquake parameters become available and (3) estimation of building damage and casualties based on estimated ground motions and intensities. The present paper elaborates on the ground motion and damage estimation methodologies used by the Istanbul Earthquake Rapid Response System with a special emphasis on validation and verification of the different methods.     

DISCUSSION ON ISSUES ASSOCIATED WITH SETBACK DISTANCE FROM ACTIVE FAULT

Living with disaster is an objective reality that human must face especially in China. A large number of earthquake case studies, such as the 2008 Wenchuan earthquake, 2010 Yushu earthquake, 2014 Ludian earthquake, have demonstrated that earthquake heavy damage and casualties stem from ground-faulting or rupturing along seismogenic active fault, near-fault high ground accelerations and building catastrophic structural failure. Accordingly, avoidance of active faults may be an important measure to effectively reduce earthquake hazard, which may encounter in the future, but how to avoid an active fault and how much a setback distance from the active fault is required to ensure that the ground faulting and rupturing has no any direct impact on buildings. This has been the focus of debate both for domestic and foreign scholars. This paper, first of all, introduces the definition of active fault. Then, quantitative analyses are done of the high localization of earthquake surface ruptures and relationship between the localized feature of the coseismic surface ruptures and building damages associated with the measured widths of the historical earthquake surface rupture zones, and an average sstatistic width is obtained to be 30m both for the earthquake surface rupture zones and heavy damage zones along the seismogenic fault. Besides, the widths of the surface rupture zones and spatial distribution of the building damages of the 1999 Chi-Chi earthquake and 2008 Wenchuan earthquake have also been analyzed to reveal a hanging-wall effect:Width of surface rupture zone or building damage zone on the hanging-wall is 2 or 3 times wider than that on its foot-wall for a dip-slip fault. Based on these latest knowledge learnt above, issues on avoidance object, minimum setback distance, location requirement of active fault for avoidance, and anti-faulting design for buildings in the surface rupture zone are further discussed. Finally, we call for national and local legislatures to accelerate the legislation for active fault survey and avoidance to normalize fault hazard zoning for general land-use planning and building construction. This preventive measure is significantly important to improve our capability of earthquake disaster reduction.     

熊坡背斜构造变形与蒲江-新津断裂活动特征

熊坡背斜位于龙门山构造带东南端的成都盆地内,是龙门山逆冲推覆构造向前推挤进入盆地内部的一个主要变形区域,与其配套发育的断裂为蒲江-新津断裂,断裂与背斜褶皱之间在构造变形模式上表现出明显的一致性。在褶皱和断裂的构造变形和活动特征上,熊坡背斜南段表现为一种不对称的褶皱,向NE方向发展表现为较为宽缓的对称褶皱形态,卷入的地层主要是中生代及其以前的地层,对蒲江-新津断裂的地貌调查结果表明,断裂没有对该区域内广泛发育的冲沟Ⅰ级阶地产生影响,而对山前发育的相当于南河(岷江Ⅰ级支流)Ⅳ级阶地的洪积台地有明显的控制作用,说明断裂活动时间应该为第四纪早期,到第四纪晚期活动减弱或是趋于静止     

基于DEM的阶地分析方法——以安宁河断裂紫马跨地区为例

河流阶地是一种最普遍的包含构造信息的地貌现象。阶地的确定与划分对于构造运动的定量研究有重要意义。文中利用数字摄影测量软件virtuoNT提取DEM,结合地貌原理,利用DEM在ARCGIS平台上建立阶地分析的处理流程,并以四川省紫马跨地区为试验区进行了阶地划分与变形分析,得到了断裂次级冲沟阶地同步位错平均约(85·4±2)m的结果,与野外检验和变形实测的结果有较好的一致性。表明利用DEM的变形阶地面提取方法具有精度高和效率高、可视化效果全面直观等特点     

青海德令哈巴音郭勒河断裂带的新活动特征

在青海德令哈巴音郭勒河北侧山前冲洪积扇上新发现了一条长约60km的逆断裂带,属于本区NNW-NWW向的柴达木盆地北缘活动断裂系内的一条次级挤压构造。断裂在地貌上表现为明显的挤压逆冲断层陡坎,晚更新世晚期以来的平均垂直滑动速率为0.41±0.27mm/a。探槽剖面确定了三次古地震事件,其年代分别为距今约32.7±1.45ka、15.54±1.32ka和3.2±0.33ka。     

汶川地震震中映秀地区地表破裂特征

汶川8级大震的震中位于映秀镇,地震在映秀地区造成了多处地表破裂,如公路拱曲、地震陡坎,坡中槽新变形等,长度达300余米.经实地全站仪和GPS测量,定量分析了地表破裂的垂直分量与水平分量以及两者之间的比值,以此揭示了映秀-北川断裂的运动性质为逆冲兼右行走滑,在映秀地区逆冲分量大于走滑分量.将本次地震造成的位错数据与震前资料对比,发现汶川地震产生的地表破裂位置与地质历史上映秀-北川断裂造成的断层位错位置是相当吻合的,说明映秀地区Ⅳ级阶地上40余米的的断层陡坎可能是地质历史时期若干次大地震的结果.     

2010年墨西哥Baja Mw7.2地震与中国玉树Mw6.9地震强地震动特征的对比研究

2010年4月4日墨西哥Baja地区发生Mw7.2地震,2人遇难;同年4月14日中国青海省南部玉树地区发生Mw6.9地震,截至2010年4月25日,已造成2220人遇难.有报道指出,玉树地震矩震级小于Baja地震,人员伤亡却远大于后者,主要原因在于玉树地区抗震设防标准低、建筑物抗震性能差.地震造成破坏程度的大小并非仅仅...     

A ground motion selection and modification method capturing response spectrum characteristics and variability of scenario earthquakes

Earthquake ground motion variability is one of the primary sources of uncertainty in the assessment of the seismic performance of civil systems. The paper presents a novel method to select and modify ground motions to achieve specified response spectrum variability. The resulted ground motions capture the median, standard deviation and correlations of response spectra of an earthquake scenario conditioned on a specified earthquake magnitude, source-to-site distance, fault mechanism, site condition, etc.     

Strong ground motion simulation during the November 1759 Earthquake along Serghaya Fault in the metropolitan of Damascus, Syria

The seismic hazard potential for metropolitan of Damascus, Syria is mainly controlled by earthquakes along Serghaya Fault which is a branch of Dead Sea Fault System. In this study, strong ground motion due to the November 1759 Earthquake along the fault of Serghaya was estimated with a numerical simulation technique. In the simulation, the Kostrov-like slip-velocity function was used as an input to the discrete wave number method to simulate the strong ground motions in a broadband frequency range. In order to model the incoherent rupture propagation which can excite large high-frequency waves, random numbers are added to arrival time of circular rupture front. MMI intensities calculated from the synthetic ground motions are compared with the observed values by Ambraseys and Barazangi (J Geophys Res 94:4007-4013, 1989). The calculated intensities are in good agreement with the observed ones at the most sites that validate appropriateness of the proposed source model. The PGA and PGV in the eastern region of Damascus city are higher than those in the western region due to the effects of local site amplification. The simulated high-frequency (1.0–6.0 Hz) ground motions for the sites in the Damascus city are higher than the design requirements defined by the Syrian building code. Furthermore, the simulated high-frequency ground motions for sites in the focal region are bigger than the design requirements in the case of the near-fault factors and are not considered. That demonstrates the appropriateness of considering the near-fault factors for a site near the focal region as introduced by the new building code.     

What Do Data Used to Develop Ground-Motion Prediction Equations Tell Us About Motions Near Faults?

A large database of ground motions from shallow earthquakes occurring in active tectonic regions around the world, recently developed in the Pacific Earthquake Engineering Center’s NGA-West2 project, has been used to investigate what such a database can say about the properties and processes of crustal fault zones. There are a relatively small number of near-rupture records, implying that few recordings in the database are within crustal fault zones, but the records that do exist emphasize the complexity of ground-motion amplitudes and polarization close to individual faults. On average over the whole data set, however, the scaling of ground motions with magnitude at a fixed distance, and the distance dependence of the ground motions, seem to be largely consistent with simple seismological models of source scaling, path propagation effects, and local site amplification. The data show that ground motions close to large faults, as measured by elastic response spectra, tend to saturate and become essentially constant for short periods. This saturation seems to be primarily a geometrical effect, due to the increasing size of the rupture surface with magnitude, and not due to a breakdown in self similarity.