震源参数对强地面震动模拟结果的影响

基于运动学震源模型,进行了不同震源参数情形下强地面震动数值模拟.结果表明,不同的破裂过程会产生差别甚大的强地面运动分布,一次确定性震源参数的模拟结果不能作为活动断层地震危害性评价的指标,只有通过大量三维地震动场模拟计算,给出地面震动评估的统计结果,才是比较合理的发展方向.由于一次三维地震动场计算耗时很大,因此解决问题的关键是如何考虑合理的震源参数.     

考虑区域特征的地震动模拟 ——以2020年伽师MS6.4地震为例

为研究伽师地区地震动的区域特征,提高地震动预测的可靠性,文中利用伽师地区近10a收集的强震动观测记录,采用非参数谱反演方法分离了地震动的震源、传播路径及场地影响,建立了反映伽师地区地震动区域特征的路径衰减、路径持时、场地线性反应等经验模型,并给出了伽师地区46次地震的震源参数(矩震级、拐角频率和应力降).文中确定的伽师...     

云南分区地震动衰减关系

受震源特性、传播路径等因素的影响,地震动特征具有很强的区域性。在近年来获取的强震动记录的基础上,根据地震地质特征和强震动记录的分布情况,将云南划分为3个区域．采用统计法和映射法,分别构建了这3个区域的地震动峰值衰减关系,并时其进行了分析和对比。     

新疆北天山地区宽频带地震动模拟关键技术研究

近年来,我国强震动观测记录数据库有了大幅扩充,一定程度上满足了重大工程抗震设防对宽频带地震动输入的迫切需求。然而,对于地震频发、强震动观测记录少的地区,宽频带地震动的数值模拟仍是确定合理地震动输入的重要途径。北天山地区是新疆经济社会发展的核心区域,现有强震动观测记录难以满足该区重大建设工程的抗震设防需求。研究构建考虑北天山地区震源机制、地质构造以及场地特征的宽频带地震动模拟方法对于高地震风险的北天山地区具有重要工程应用价值。宽频带地震动模拟方法由具有强区域特征的高频地震动随机模拟方法及基于求解无限域波动问题的低频地震动模拟方法组成。本文围绕北天山宽频带地震动模拟方法构建中的关键问题展开研究:针对高频地震动模拟,主要研究中小震震源模型的构建及非平稳地震动合成所需的群速度模型;针对低频地震动模拟,主要研究无限域波动数值模拟中高精度人工边界的构建,以尽可能缩小模拟工作区和提高计算效率。取得的研究成果如下:(1)北天山地区震源和路径传播模型构建。利用该地区2009—2015年843个M_L≥3.0地震记录,采用多台多地震联合反演方法建立了该地区的路径衰减、台站场地响应以及震源谱模型。结果表明,北天山地区中小震震源谱具有分段特性:4级以下地震的震源谱与引入震源谱高频衰减因子(κ=0.003)的Brune模型在统计意义上基本一致,4级以上地震的震源谱逐渐偏离Brune模型,呈现较为明显的双拐角频率特性;另外,震源谱存在分区差异,库拜盆地、塔里木盆地内地震的震源谱在高频段衰减更为显著。(2)北天山地区等效群速度模型构建。在已有基于等效群速度模型合成地震动的工作基础上,引入震相微分计算方法改进了等效群速度的计算方法;提出应用测震记录P波到时构建最快波群速度模型,分析了最快波群速度选取对等效群速度模型构建的影响;基于北天山地区的强震动观测记录,统计得到该地区的等效群速度模型。等效群速度模型引入到高频随机模拟方法的算例结果表明,基于等效群速度模型考虑地震动非平稳特征可给出更为合理的地震动模拟结果,对于面波发育的深厚覆盖层场地影响尤为突出。(3)高精度人工边界条件完美匹配层构建。完美匹配层内场方程和界面条件通常分别采用复坐标延伸技术变换强形式无限域内波动方程和界面条件得到,其构建过程相互独立,可能出现匹配不合理而引发的数值失稳、计算精度低下等问题。为此提出采用复坐标延伸技术变换弱形式无限域波动方程以构建完美匹配层的方法。弱形式波动方程耦合了波动方程及界面条件,规避了变换后所得场方程与界面条件的匹配不合理问题。新方法可直接给出弱形式匹配层,结合勒让德谱元建立了弹性介质近场波动谱元模拟方案。利用算例验证了新方案的精度及数值稳定性。(4)新源—和静6.6级地震地震动场的数值模拟。2012年6月30日新源—和静地震是北天山地区近50年来发生的最大地震,测震及强震动观测记录均较为丰富。本文应用反演所得滑动分布和随机滑动分布分别拟合了强震动台站的地震动时程,对比分析了拟合反应谱与观测记录反应谱的差异性;模拟了该地震的烈度分布图,分析其与实际调查烈度图和基于新疆常用地震烈度衰减关系计算的烈度图之间的差异,探讨了破坏性地震发生后应用高频随机有限断层方法生成地震烈度分布图的可行性。     

汶川地震强地面运动模拟

基于确定性震源模型的方法主要用于计算低频(11 Hz)地震动常用经验格林函数法或随机方法,对低频地震动模拟不够准确．本文在确定性震源模型方法基础上,尝试采用分解给定的震源模型的方法来模拟宽频带(0.1——10 Hz)强地面运动,即采用分级离散断层面和分解断层面破裂单元上升时间的方法,增加震源时间函数中的高频信号,从而避免了对地震记录丰富程度和准确性的依赖．文中模拟计算了汶川MS8.0地震在8个地震观测台的地震动,将模拟结果和观测记录进行了加速度时程曲线和傅里叶振幅谱的对比分析．对比结果显示,模拟估计的地震动峰值加速度和持续时间与观测记录的数据基本在plusmn;50%的精度范围内相同,傅里叶振幅谱显示模拟结果有得到10 Hz左右的高频成分. 四川盆地中的台站模拟结果高频衰减比观测记录要快,原因是模拟过程没有考虑场地效应.对强地震动模拟还是要综合考虑震源、传播路径和场地的影响．研究结果表明,此改变震源输入的确定性方法可应用于模拟近断层宽频强地面运动．      

强震动记录Flatfile的研究进展

为了合理、方便地使用日益增长的强震动记录,一些国家和地区开始编制强震动记录的直接文件(Flatfile)。本文在分析第16届世界地震工程会议中与强震动记录相关论文的基础上,依据强震动数据来源的区域范围和编制目的,对强震动记录的Flatfile进行了分类;通过结合对典型的Flatfile文件分析,阐述了强震动记录Flatfile应具备震源、路径和场地等重要信息;在简述Flatfile建设发展趋势基础上,结合我国强震动记录数据的管理现状,对我国强震动记录Flatfile的编制提出了建议。     

基于经验格林函数法的2021年MS6.4漾濞地震近场强震动模拟

由于震中附近强震台分布不均,文中联合使用近场2个国家强震动观测台网的强震台和7个云南地震预警台网烈度台的强震记录,采用经验格林函数法构建了特性化震源模型,并利用此模型对近场强震动进行了模拟。结果表明：烈度台的记录可与强震台的记录联合,共同作为强震动模拟的对象,但应注意区分二者的有效频带;在0.20～30.0Hz频带,在53YBX台处的NS分量上,模拟结果的伪加速度反应谱较好地再现了0.1s处的峰值,在EW分量上,合成的速度波形虽然幅值较低,但较好地再现了速度脉冲波段;在53DLY台处的合成波形较好地再现了约2s的长周期地震动;在0.50～30.0Hz频带,合成波形和反应谱与信噪比较高的烈度台的记录较为一致。文中确定的用于模拟强震动的特性化震源模型由一个强震动生成域构成,其面积和相应的短周期范围内加速度震源谱的水平段幅值与地震矩的关系均遵循经验标度律。     

区域介质品质因子对地震动参数衰减的影响

本文考虑介质环境表观品质因子,根据美国西部强地震动记录确定了地震动衰减模型中的参数,在不考虑震源机制细节差异的条件下,分析比较了八个地区由于表观品质因子Ｑ值不同导致的地震动加速度傅里叶幅值谱和均方根强度衰减关系的差异。     

相对局部区域震源参数随机不确定性经验关系研究

在进行未来破坏性地震的强地面运动数值模拟时,震源参数选取的准确性对地震动预测的结果影响很大。震源参数的确定存在很多不确定性因素,既包含随机的不确定性因素,又包含认知的不确定性因素。本文在大量地震事件及文献调研的基础上,运用统计学方法对具备随机不确定性特征的震源参数进行统计研究,以震源参数经验公式的形态建立解释其随机性和不确定性的数学模型。为了研究局部地区震源参数的定标关系特征,获得更加适用于局部地震密集区域,尤其是包含中国大陆地区在内的局部区域的震源参数的经验关系,本文从GCMT地震目录中选取了1 700多个M_W≥5.5的地震事件,运用统计学方法研究地震密集地区的震源参数经验关系,包括震级、地震矩、破裂面积等,增加了相对较大的局部范围内凹凸体的地震样本数量,从统计学角度计算更加适合局部区域的震源参数的经验关系。统计结果表明:局部区域震例获得的震源参数的经验关系与不限区域震例获得的经验关系存在差异,尤其是涉及到断层破裂面积、凹凸体相关参数时差异较大,局部区域内震例获得的震源参数的经验关系将更具有代表性。应用本文获得的相对局部区域的经验公式计算未来破坏性地震的强地面运动所需的震源参数时,获得的地震动预测结果将更能体现目标区域真实的地震动特征,进而提高地震动预测结果的可靠性。      

芦山7.0级地震强震动记录及其震害相关性

2013年4月20日芦山地震中的强震动记录是我国自2008年汶川地震后再一次比较全面地获得的高质量的数字强震动记录。国家数字强震动台网共获得3分量自由场记录114组,成都地震烈度速报台网获得63组。文章对强震动记录进行了常规处理,统计了强震动记录随断层距的数量分布情况,绘制了空间地震动加速度等值线图。结合芦山地震震源机制解和破裂过程研究成果,选取典型记录,分析加速度、速度时程的波形、振幅等特征,识别了此次地震滑冲现象,估算了竖向最大永久位移。通过利用观测数据与国外的地震动预测公式对比,分析了不同周期反应谱地震动幅值及加速度反应谱衰减规律,阐明了此次地震的地震动在近场高频成分较卓越的特点。震后现场考察了3个典型强震动台站附近建筑物震害,分析了地震动与工程震害的相关性,地震烈度的评定反映了地震破坏的程度。     

An explanation of the large PGA value of 2013 Ms7.0 Lushan earthquake at 51BXD station through topographic analysis

In Ms7.0 Lushan earthquake, a large amount of strong ground motion recordings were collected. In this paper, we analyze the recordings carefully. The abnor- mality of ground motion recordings is identified through a log linear regression. In the station of 51BXD, the PGA value has exceeded 1 g, which is the biggest peak ground acceleration （PGA） value obtained from all recordings in this earthquake. The log linear relation shows the PGA value in this station is abnormally large. As this station is located on the footage of a hill, the topographic amplifi- cation factor is explored in order to explain this abnor- mality. Through 3D numerical modeling using spectral element method with transmitting boundary conditions, the amplification factor is quantized. In this station, the topo- graphic amplification is highly polarized in the direction of East-West which agrees with the empirical recordings. This research result suggests us in future directionality of topographic amplification should be considered in the aseismic design.     

A note on the useable dynamic range of accelerographs recording translation

Since the late 1970s, the dynamic range and resolution of strong motion digital recorders have leaped from 65 to 135 dB, opening new possibilities for advanced data processing and interpretation. One of these new possibilities is the calculation of permanent displacement of the ground or of structures, associated with faulting or with non-linear response. Proposals on how permanent displacements could be recovered from recorded strong motion have been published since 1976. The analysis in this paper concludes that permanent displacements of the ground and of structures in the near-field can be calculated provided all six components of strong motion (three translations and three rotations) have been recorded, and the records are corrected for transducer rotation, misalignment and cross-axis sensitivity.     

中国大陆的强震动观测

简要综述了强震动观测的目的和意义及我国大陆强震动观测的发展过程,讨论并展望了我国强震动观测的发展策略和前景。     

In-plane response of two-story structures to near-fault ground motion

Linear and non-linear responses of a two-story structural model excited by near-source fault-normal pulse and fault-parallel displacement are investigated. For the considered linear system, the multi-component differential-motion effects amplify the first-story drifts 3.0–4.0 times relative to the excitation by synchronous horizontal ground motion only. The contribution of horizontal differential ground motion to the total drift is about two thirds, and the contribution of vertical and rocking differential ground motions is about one third. For the considered nonlinear system, the effects of vertical and rocking differential ground motions become more significant for the second-story drifts. The horizontal differential ground motion amplifies the first-story drifts, but the simultaneous action of horizontal, vertical, and rocking differential ground motions can amplify the first- and second-story drifts by more than 2.0 times relative to the drifts computed for uniform horizontal ground motion only.     

芦山地震地震动上下盘效应研究

2013年4月20日的芦山7.0级地震是继2008年5月12日汶川8.0级特大地震之后,发生在龙门山断裂带上的又一次大震级逆冲型地震.与汶川地震相比,芦山地震的发震断层没有地表出露,断层的滑动角更大,其逆冲性质更强烈.本文挑选了芦山地震中断层距小于200km的45条强震动记录,基于地震动衰减关系进行统计分析,对比了上盘和下盘台站地震动参数相对于衰减关系的对数残差.结果表明：芦山地震的上下盘效应明显,近断层上盘地震动的高频成分要高于同断层距的下盘;上盘地震动衰减要明显快于下盘.地震动衰减关系用简单的一个距离参数很难描述近场断层尺寸效应的影响,也很难模拟地震动上下盘效应.因此,在近场强地面运动模拟中,应多考虑有限断层模型,以模拟断层的尺寸效应.     

水利水电工程强震监测和强震监测仪器

阐述了强震监测在实际工程中的作用,国内外强震监测的基本情况以及我国水利水电工程领域的强震安全监测的进展与现状,介绍了强震监测仪器的基本原理、特性及目前国内强震仪研制生产的技术水平和成果.介绍了水电工程领域强震监测工作中存在的实际问题.最后展望了强震监测工作在我国水电工程领域的发展趋势.     

长期极移的成因

依据宋贯一等(2006)发表的"极移的成因及其移动特征"一文中的研究成果,对其中极移反向(由东向西)运动的时问分布进一步研究得知:在地球公转所处的四季位置中,自转极(北极)反向运动时间仅发生在当年的11月1日(立冬日为11月7、8日)到第二年的2月15日(立春日为2月4、5日)这一段时间之内;其它时间(季节)均为自转极正向(由西向东)运动时段.对比冬至日前后和夏至目前后极移的运动方向可知,它们相对太阳的运动方向虽然相反,由于它们分别处在轨道的东、西方向的两侧,从空间上看来,它们的运动方向却是一致的(即都是向自转极以西运动).基于上述原因,经过一个回归年的太阳光压激发之后,极移运动轨迹的年平均位置向CIO(国际极点)的西侧移动了.在下一个周年期激发时段,上述现象将在上一回归年极移年平均位置的基础上继续进行,逐年累积即形成长期极移.这就是周年期激发机制引起的长期极移及观测的极移运动轨迹均落在CIO西侧的原因.     

Advanced sensitivity calibration of the Los Angeles strong motion array

Results are presented of recent sensitivity calibration of 76 accelerographs (SMA-1) of the Los Angeles Strong Motion Array. These have pendulum-like transducers and optical recording system. One characteristic of their design is off-axis sensitivity, which is magnified by transducer misalignment. A new calibration procedure was applied, which considers off-axis sensitivity and measures the angles of misalignment (φ and ψ), as well as the incident angle of the light beam onto the film (θ₀). These are required (1) for accurate estimation of sensitivity, and (2) for proper instrument correction of recorded accelerograms which considers also cross-axis sensitivity and misalignment. These effects are important near large acceleration peaks (approaching and exceeding 1g), e.g. like the ones recorded near the source of the 1994 Northridge earthquake (M_L=6·4). This earthquake was recorded by 65 stations of the Los Angeles Strong Motion Array, at epicentral distances from 2 to 85 km. Histograms showing distribution of the misalignment angles, light beam incidence angle θ₀ (for unloaded position) and the transducer sensitivities are presented. These indicate that the misalignment angles are typically 1–1·5°, but may also be 3–4°. Angle θ₀ (usually neglected), is mostly between ±8°, but may reach ±12°. Assuming θ₀=0 leads to systematically smaller values of the measured sensitivity (e.g. by ∼3% for θ₀=8° and ∼4% for θ₀=12°). Comparison of the newly measured sensitivities with those measured prior to installation (in 1979/1980), s^old, shows that, in general, the new values are systematically smaller. The difference is typically within 5 per cent, but in some cases is as large as 10 per cent. Other principal sources of the observed differences and their mechanisms are discussed. Those include long-term changes in the transducers (e.g. change of stiffness, reflected in changes of the natural frequency) and differences in the calibration procedure (e.g. errors associated with manual reading film records with tilt test data, and with transducer and instrument housing misalignment). The presented results may be considered typical of similar strong motion arrays worldwide. © 1998 John Wiley & Sons, Ltd.     

Seismic control of rocking structures via external resonators

Tall rigid blocks are prevalent in ancient historical constructions. Such structures are prone to rocking behaviour under strong ground motion, which is recognizably challenging to predict and mitigate. Our study is motivated by the need to provide innovative nonintrusive solutions to attenuate the rocking response of historical buildings and monuments. In this paper, we examine a novel scheme that employs external resonators buried next to the rocking structure as a means to control its seismic response. The strategy capitalizes on the vibration absorbing potential of the structure-soil-resonator interaction. Furthermore, the benefits of combining the resonators with inerters in order to reduce their gravitational mass without hampering their motion-control capabilities are also explored. Advanced numerical analyses of discrete models under coherent acceleration pulses with rocking bodies of different slenderness ratios under various ground motion intensities highlight the significant vibration absorbing qualities of the external resonating system. The influence of key system parameters such as the mass, stiffness, and damping of the resonator and those of the soil-structure-resonator arrangement are studied. Finally, a case study on the evaluation of the response of rocking structures with external resonators under real pulse-like ground-motion records confirms the important reductions in peak seismic rotational demands obtained with the proposed arrangement.     

地震动强度与地震烈度速报研究

本在总结了美、日等国家和我国大陆与台湾地区基于实时或近实时强震台网的地震动强度（烈度）速报方法的基础上，对我国地震动强度（烈度）速报及计算机软件编制中的关键技术问题进行了讨论。