首都圈跨断层流动形变观测资料映震能力及场地监测能力分析

首都圈最早建立跨断层流动形变监测网始于20世纪60年代末,主要布设在北京周围广大地区,覆盖了主要活动断裂带.在过去的40多年里,首都圈地区及附近发生了多次强震,如1976年唐山7.8级、1989年大同6.1级和1998年张北6.2级地震等.本文首先对首都圈地区的跨断层流动形变观测资料进行了映震能力分析,然后探讨了监测场...     

张北6.2级地震前的地壳形变特征

介绍了１９９８年１月１０日张北６．２级地震前华北地区,主要是首都圈地区的地壳形变特征。分析了ＧＰＳ结果、跨断层形变观测以及定点台站观测的异常信息。认为张北地震前的地壳形变异常大部分是“场兆”异常;张北震中区在震前至少半年是处于形变闭锁阶段;地壳形变的前兆发展在总体上存在由东南向西北迁移特征。     

华北地区震前断层异常活动方式

分析了华北地区跨断层形变资料, 研究了唐山、 大同及张北地震前断层异常活动方式。 结果表明, 震前存在显著的断层异常活动; 断层异常活动方式具有构造控制特征,并与孕震机理有关; 地震孕育过程中有可能出现多次应力集中; 从断层不可逆异常活动地区的分布推测, 唐山地震缓解了延怀地区的地震危险性, 大同地震缓解了紫荆关-狼山断层一线的地震危险性; 张北地震断层异常活动呈松弛变化, 首都圈及邻近地区地震活动将趋于缓解。     

首都圈断层网络形变前兆与大同6.1级地震关系的研究

本文用蕴震系统信息合成方法(ISSS,Information Synthesis of Seismogenic System)来描述和评估首都圈蕴震系统的自组织演化过程。通过前兆信息合成寻求系统由稳态—非稳态—奔向吸引子新稳态的判据与可能的指标。结果表明:无论是对蕴震大系统(首都圈断层网络)综合形变前兆异常的信息合成,还是对子系统(首都圈几条主要断裂带)前兆异常的信息合成、或是动态灰箱识别异常频次的等权和加权合成,都显著地提高了大同6.1级地震前兆信息的可靠性和清晰度,为首都圈今后地震趋势的评估与预测提供了可信的判据和指标。     

山西带断层形变特征研究

本文基于山西带跨断层形变测量的全部历史资料, 通过对1989年大同—阳高6.1级和1998年张北6.2级二次地震前断层形变群体性异常变化的分析, 对山西带断层形变特征及与强震孕育发生之间可能存在的关系进行了系统研究, 指出了断层形变在空间上和时间上存在的相对性特征, 可供用震例中总结出的断层形变规律跟踪预测和研究未来震情的趋势时参考, 同时对当前华北震情, 特别是山西带震情的跟踪研究工作提出了建议和看法。     

用主成分分析方法综合分析鲜水河断裂带跨断层形变资料

本研究以鲜水河断裂带为例,通过断层三维活动参数、断层活动信息合成和主成分分析等方法,对汶川8.0、芦山7.0和康定6.3级地震前后鲜水河断裂带地区的跨断层形变资料进行了综合分析;计算断层水平扭错速率、水平张压活动速率的各个主成分和能够反映断层总体活动水平的综合指标W.结果表明:主成分分析方法能够最大限度地保留原始信息,...     

华北北部三次地震前的应变释放加速特征

强地震发生前,区域地震活动往往出现应变释放加速(AMR)现象。本文以华北地区的1976年唐山7.8级地震、1998年张北6.2级地震、2006年文安5.1级地震作为目标地震,分别分析三次主震前4~8年期间、40~120 km半径范围内的AMR现象及其特征。结果显示,唐山7.8级地震与张北6.2级地震之前均不同程度出现AMR异常,但文安5.1级地震之前并未出现。另外,本研究发现80 km半径可能是研究区寻找AMR异常有效、合理的空间扫描尺度。基于这三个震例研究的认识,本文进一步针对晋冀蒙交界地区和首都圈地区进行分析计算,结果识别出首都圈地区至目前存在AMR异常地区,这可作为判定华北北部未来强震危险性的参考。     

降水与地震关系的讨论

引用地下流体异常的判定方法,即月均值滑动平均法和从属函数法,处理了北京丰台、山西定襄、河北昌黎3个地震台的降水资料。结果表明,在降水的原始曲线上,降水量异常显示比较模糊;而经过定量处理后,降水存在着明显的中期和中短期异常变化。降水异常与1976年唐山7.8级、1981年丰镇5.6级、1989年大同5.9级、1998年张北6.2级及2006年文安5.1级等多次地震的对应关系良好;与水位、水氡、地形变异常之间有着十分密切的呼应关系。降水异常与地震的关系可用"水诱发机理"来解释;降水异常属于外因性前兆,为非必震信号。降水异常与发震时间的关系密切,可用于地震的中短期预测,其预测期为4～14个月。     

华北地区震前断层水平异常活动特征

分析了首都圈及邻近地区跨断层基线测量资料, 研究了唐山、大同及张北地震前后断层水平异常活动特征。结果表明, 震前在震中外围存在显著的断层水平异常活动, 监测断层水平活动是地震预测的有效手段; 同一测点震前断层水平异常活动具有相似性特征; 唐山地震前在震中附近一定范围内出现的断层水平异常活动, 具有断层预位移性质。     

印尼8.7级地震在河北省的震后效应初探

2004年12月26日印尼苏门答腊发生M8.7级地震时,我国大量的形变、地下水位等台站记录到了丰富的同震效应,河北省的前兆观测资料多数也出现明显的同震变化.本文通过分析河北省境内前兆资料的同震变化特征,认为印尼M8.7级地震可能使河北省中东部地区产生了断层的错动,促使一年半后发生文安M5.1级地震.     

小波分析在GPS位移时间序列特征中的应用

使用福建GPS台网2004年3月—2008年10月的连续观测资料,对各基准地震站原始数据进行处理,得到位移时间序列,进行初步分析。在此基础上,采用小波分析方法提取时间序列的时频特征,从而得到非线性变化信息,为GPS在大地震前获取前兆资料提供探索方向,进而通过对位移时间序列异常变化与区域地壳运动关系的研究,探讨两者间的内在联系。     

Non-linear canonical correlation analysis in regional frequency analysis

Hydrological processes are complex non-linear phenomena. Canonical correlation analysis (CCA) is frequently used in regional frequency analysis (RFA) to delineate hydrological neighborhoods. Although non-linear CCA (NL-CCA) is widely used in several fields, it has not been used in hydrology, particularly in RFA. This paper presents an overview of techniques used to reproduce non-linear relationships between two sets of variables. The approaches considered in this work are based on NL-CCA using neural networks (CCA-NN), coupled to a log-linear regression model for flood quantile estimation. In order to demonstrate the usefulness of these approaches in RFA, a comparative study between the latter and linear CCA is performed using three different databases from North America. Results show that CCA-NN is more robust and can better reproduce the non-linear relationship structures between physiographical and hydrological variables. This reflects the high flexibility of this approach. Results indicate that for all three databases, it is more advantageous to proceed with the non-linear CCA approach.     

Approximate incremental dynamic analysis using the modal pushover analysis procedure

Incremental dynamic analysis (IDA)—a procedure developed for accurate estimation of seismic demand and capacity of structures—requires non‐linear response history analysis of the structure for an ensemble of ground motions, each scaled to many intensity levels, selected to cover the entire range of structural response—all the way from elastic behaviour to global dynamic instability. Recognizing that IDA of practical structures is computationally extremely demanding, an approximate procedure based on the modal pushover analysis procedure is developed. Presented are the IDA curves and limit state capacities for the SAC‐Los Angeles 3‐, 9‐, and 20‐storey buildings computed by the exact and approximate procedures for an ensemble of 20 ground motions. These results demonstrate that the MPA‐based approximate procedure reduces the computational effort by a factor of 30 (for the 9‐storey building), at the same time providing results to a useful degree of accuracy over the entire range of responses—all the way from elastic behaviour to global dynamic instability—provided a proper hysteretic model is selected for modal SDF systems. The accuracy of the approximate procedure does not deteriorate for 9‐ and 20‐storey buildings, although their dynamics is more complex, involving several ‘modes’ of vibration. For all three buildings, the accuracy of the MPA‐based approximate procedure is also satisfactory for estimating the structural capacities for the limit states of immediate occupancy, collapse prevention, and global dynamic instability. Copyright © 2006 John Wiley & Sons, Ltd.     

Gravity ideal-body analysis

Summary This short note contributes to the methods of computing the bounds on some properties of the source of measured data.     

地震作用下曲线梁桥结构响应及敏感性分析

为研究不同设计参数对曲线梁桥地震响应的影响以指导结构抗震设计,对不同支承约束曲线梁桥地震响应及地震需求敏感性进行分析。采用增量动力分析（IDA）方法对比分析了不同支承约束曲线梁桥的结构地震响应变化趋势;采用Tornado图形法对不同结构参数影响程度进行了排序,找出了对结构地震需求影响显著的参数。结果表明:采用板式橡胶支座桥梁因支座易发生滑移而导致上部结构位移较大,但降低了下部结构响应,设置固定墩后,下部结构损伤显著增加;对于采用板式橡胶支座和铅芯橡胶支座的曲线梁桥,墩高及跨径对墩底曲率需求影响较大,而对于固定墩为墩梁固结形式和采用盆式橡胶支座的曲线梁桥,跨径及跨数对墩底曲率需求影响较大;对于采用不同支承约束的曲线梁桥,墩高和曲率半径对桥台位移需求影响较大,仅次于地震动参数PGA。     

基于增量动力分析方法的砌体结构地震易损性分析

砌体结构是一种脆性结构,变形能力和承载力均较低,因取材方便、施工简单和造价低等优势在中国被广泛应用。为了评估砌体结构的抗震性能,本文基于增量动力分析（Incremental Dynamic Analysis,IDA）方法研究了多层砌体结构的地震易损性,分析了影响砌体结构地震易损性的主要因素以及群体多层砌体结构地震易损性。研究结果表明:在相同场地条件情况下,砌体结构的房屋层数、砌筑砂浆强度、设防烈度和墙体面积率对结构的地震易损性影响较明显;当结构层高在2.8~3.3 m之间时,层高对结构地震易损性的影响不大。抗震设防砌体结构抗震能力比不设防结构有明显提高,说明构造柱和圈梁等构造措施能显著提高砌体结构的抗倒塌能力,这与目前的基本认识相同,也证明了增量动力分析方法的有效性。     

Equating incremental dynamic analysis with static nonlinear analysis at near-field excitation

In an incremental dynamic analysis(IDA) using a set of ground motion records,nonlinear time history analysis needs to be performed on structures.It is well recognized that IDA calls for high computational efforts and the results are highly sensitive to selected ground motions.As a result,alternative static methods are needed.This study aims to introduce a new double-stage(N1- N2) static method to estimate capacity curves of MR frames.The technique is regulated to resemble IDA results with specific emphasis on near-field ground motions.Using an ensemble of 56 near-field earthquake records,required ID As have been carried out for SAC-Los Angeles 3-,9- and 20-story buildings and an additional 15-story building.The results of the proposed static method are compared with those from IDA,displacement-based adaptive procedure(DAP),and multimodal procedure(MMP).The results indicate that in addition to enhanced accuracy,very little time is required in the case of N1-N2 method.Thus,for the 3-story structure,the time required is less than 1 minute.The proposed N1-N2 method shows the best accuracy in terms of lateral mechanisms for the 15-story frame while for the other cases,the first mode load pattern leads to the best accuracy.     

Critical analysis of the alternating direction implicit method of aquifer analysis

The alternating direction implicit method, when used for aquifer analysis, is liable to lead to erroneous results. By a careful examination of the effect of various factors, such as external boundaries, variable mesh intervals, internal boundaries with fixed heads, re-entrant boundaries and leakage, the occasions when these errors are serious have been identified. Techniques are described which can avoid these errors and lead to reliable numerical solutions.     

Seismic analysis of sliding wedge: extended Francais–Culmann's analysis

Pseudo-static analysis is commonly used to design earth structures. Most pseudo-static methods of analysis require a computer program. This paper presents a simple closed form solution of seismic stability analysis by extending Francais–Culmann's analysis. The analysis is valid for a slope with the most critical planar mechanism and under the influence of horizontal and vertical earthquake accelerations. The resulting permanent displacement is discussed and demonstrated using several real earthquake records. The simplicity of extended Francais–Culmann's solution allows it to be used for preliminary design and classroom instruction.