豫北重大垂直形变异常的成因研究

１９８０年以来，豫北安阳至清丰水准测线上出现了较大的地面沉降漏斗。通过对标石稳定性、采矿影响、地壳构造运动特别是地下水与地壳形变关系的分析研究，认为漏斗形成的原因与地下水和地层有关，并非地震前兆异常。     

陕西几例特殊的无震异常及其成因分析

介绍了陕西省前兆台网记录到的几例特殊的无震异常。分析了这些异常产生的原因。认为１９８６年和１９９６的渭南双王井水位的２次无震异常与渭河的洪峰有关;１９７７年韩城地震台地倾斜特大异常可能与黄河水位变化有关;１９８３年安康地震台地倾斜特大异常与该地区特大洪水有关;１９９６年和１９９８年三原井水位的２次特大异常可能与附近的冯村水库蓄水有关。     

陕西几例特殊的无震异常及其成因分析

介绍了陕西省前兆台网记录到的几例特殊的无震异常．分析了这些异常产生的原因．认为１９８６ 年和１９９６ 年渭南双王井水位的２ 次无震异常与渭河的洪峰有关;１９７７ 年韩城地震台地倾斜特大异常可能与黄河水位变化有关;１９８３ 年安康地震台地倾斜特大异常与该地区特大洪水有关;１９９６ 年和１９９８ 年三原井水位的２ 次特大异常可能与附近的冯村水库蓄水有关     

岫岩MS5.4地震前烟台形变异常特征及机理分析

运用直接调和分析和速率合成方法对岫岩地震前后烟台形变观测资料进行了处理分析。结果表明,岫岩5.4级地震前,烟台地区形变观测资料出现了短临前兆异常,此次异常很可能是岫岩发震断层活动引起了相关的蓬莱-威海断裂活动,最终导致区域应力场增强的结果。     

乌鲁木齐形变站资料异常分析

引言新疆乌鲁木齐形变站是一个大地形变台站 ,其基本任务是采用高精度的测量仪器监测断裂的运动 ,为地震的研究和中、短期预报提供准确、完整的观测资料。目前主要的观测手段是跨断层短水准测量。乌鲁木齐形变站于 1 981年 1 0月埋点 ,1 982年 5月正式投入观测。当时的网形为旧三角形 N1 EW。 1 985年 9月 ,N1 点向南移 3 0 m至 N点 ,构成新三角形 NEW(图 1 ) ,并于 1 986年 1月开始观测。 1 986～ 1 988年为验证阶段 ,因此文中资料从 1 988年开始选取。笔者图 1　乌鲁木齐形变站场地示意图Fig.1　 Sketch of the observation site of …     

海原形变观测资料异常分析

对海原台CZB-1型竖直摆钻孔倾斜仪记录到的地表倾斜方向的异常变化进行了分析,同时对该台YRY-4型分量应变仪依据自检方法表现出的压缩及伸张性异常进行了提取,得出以上两测项观测资料在宁夏南部发生的3次Ms3．0级以上有感地震的2次地震前出现了一定的异常信息,与地震赢救蚺蕴。     

中条山北麓断裂形变异常分析

以运城盆地及周边M_L5.0以上地震活动,与盆地的主控构造中条山北麓断裂的活动关系进行研究,表明地震与断层(活构造)的活动有直接关系。目前,对活断层进行形变测量和地球物理场的动态观测是揭示地壳运动最为有效的手段。     

台湾海峡地震定点形变的异常分析

结合定点形变前兆异常的常用判定标准,用多种数学方法处理了厦门台与漳州台1991～1995年水平摆地倾斜资料,发现在9,16海峡地震之前,两个台站的资料都表现出不同程度的年变规律畸变、γ因子异常、一阶差分法异常、滤波法异常等多种地形变前兆指标异常。     

福建省数字化形变资料的异常分析

为了提取中短期地震前兆信息,对福建省2006～2008年数字化形变观测整点值资料进行了二进小波多分辨率分析,结果表明：小波分析结果的细节部分dn主要包含周期为2n-2a＋1小时的信号,而近似部分‰包含所有周期大于2n＋1小时的信号;在此期间,福建省及其邻近地区的中强地震发生前,多数形变观测台站或测项同步接收到了周期大约为21～43d幅度较大的异常信号,这些信号可能是地震前兆。     

强震前形变潮汐异常判识与机理研究

通过对永胜倾斜、侯马应变数字化固体潮汐观测资料的分析研究,认为当孕震系统进入失稳的临界状态时,微量级的形变突变可能受到引潮力的触发作用. 阶变异常与引潮力的方向、断层走向的剪应力的大小和方向有一定的相关性. 本文首次将形变异常与附加引潮力的关系进行研究,以探索临震前形变异常的物理机制及判识方法.      

The mechanism of unsaturated flow through a volcanic ash layer under humid climatic conditions

It is very interesting and meaningful to investigate the rainfall-groundwater recharge process under the humid climatic condition of Japan, where mean annual precipitation is about 1600 mm. The present study has investigated soil water movement in the unsaturated zones of a volcanic ash layer, called the ‘Kanto Loam formation’, using environmental tritium as a tracer. The site selected is a flat ground surface on a terraced upland which has a deep unsaturated zone (about 20 m) with a relatively high water content (about 70 per cent) consisting of nearly uniform Kanto Loam formation. The tritium concentrations in groundwater, soil waters having different matric potentials, precipitation, and the seepage water moving through the formation into a man-made cave were measured to characterize the rainfall-groundwater recharge process and the effect of large pore spaces in the formation mentioned by previous studies. Because of the humid climate of Japan, there appears to be a unique soil water flow characteristic which may involve percolation through large pore spaces during heavy rainfall. However, in a fine grained and high water content soil like the Kanto Loam formation, the existence of this flow through large pore spaces does not have a significant effect upon the whole recharge process. The recharge model of displacement flow with dispersion is useful in estimating the tritium concentration profile of soil water. The calculated result shows a recharge rate of 2.5 mm/day. The value obtained reflects the hydrological characteristics of the uplands covered with volcanic ash.     

环境激励下一种基于免疫机制的结构损伤诊断方法

结构状况发生改变时,结构的振动特性将发生变化。免疫算法能有效检测出振动特性的变化。本文将环境激励下的结构响应重构相空间,对其进行奇异值分解后,选择适当个数的奇异值构造特征参数集合,应用反向选择算法进行异常值检测,以ASCE学会提出的基准结构为对象进行研究,讨论了不同个数的特征参数对检测结果的影响。分析表明,该算法能有效地判断结构状况的变化。     

On the stability of colonnade structural systems under static and dynamic loading conditions

The structural behavior of colonnade structural systems subjected to static and dynamic loading is investigated to identify the main factors affecting the stability and to improve our understanding of their behaviour. In particular, the discrete element method of analysis is utilised to study the static and dynamic behaviour of a typical section of the two storey colonnade of the Forum in Pompeii. Static analysis indicated that the failure of colonnade structures occur at higher friction angles as the weight above the structure decreases and so a sudden collapse can occur when parts of the monument are disassembled. For the dynamic analysis, the mechanical behavior of the colonnade was investigated for both harmonic and real seismic excitations. For excitations with relatively low dominant frequencies, the primary response is rocking; as the excitation frequency increases, the response becomes more complicated demonstrating both sliding and rocking movements. It was also shown that the construction methods used in ancient times, such as multi-block segmented trabeations and solid block beam, have quite significant impact on the mechanical response of the structures under static and dynamic loading.     

特殊复杂场地条件下桥梁结构地震易损性研究现状及发展趋势分析

考虑到桥梁地震易损性分析中场地条件影响的不确定性,本文主要针对流水冲刷环境、可液化场地、近断层场地、氯盐侵蚀环境和冻土场地等特殊复杂场地条件对桥梁结构地震易损性的影响特征和机理进行了总结归纳,并提出了尚待进一步研究的关键问题.结果 表明:特殊场地地震响应的复杂性和桥梁结构的特殊性相叠加,给复杂场地条件下桥梁的抗震性能评...     

Numerical analysis on dynamic deformation mechanism of soils under blast loading

Soil is considered as a three-phase medium consisting of solid particles, water and air. Its behavior is very difficult to predict, especially under high rate blast loading. In this study, a new three-phase soil model for shock loading is employed to facilitate a full simulation of explosion and the subsequent stress wave propagation in soils. Upon validating the model, extended numerical calculations are carried out and the results are analyzed to demonstrate the change of characteristic parameters of the soils, the inherent distribution of the pressure on individual phases and hence the deformation mechanisms of the soils under blasting loading. Two primary deformation mechanisms exist, one is the deformation of the soil skeleton formed by the solid particles; the other is the deformation of all individual soil phases. It is found that the response of soil near the charge is dominated by the second mechanism while the first mechanism dominates in areas beyond a certain scaled range. The location of the transition zone depends primarily on the initial state of the soil. The results are useful for establishing rational and practical soil models for engineering applications concerning blasting.     

The electronic thermodynamics of iron under Earth core conditions

The LMTO method is used to calculate the electronic band structure of iron in the ϵ-phase (hcp) and in the γ-phase (fcc) for seven compressions from 4 to 980 GPa. The electronic specific heat c_υe(T) is calculated for each phase by numerical integration from the resultant density of states. Previous work is thus supported for γ-iron and extended to ϵ-iron, the most likely inner core component. A simple parameterization of c_υe is given for use in making geophysical estimates. Other thermodynamic parameters which are calculated are the electronic free energy, the thermal electronic pressure, and an electronic Gruneisen parameter, γ_e.Recent studies of liquid iron and iron alloys indicate that the density of states at the Fermi level does not differ much from that calculated for pure crystalline iron. We cautiously apply our results to the outer core and find that c_υe = 1.7 ± 0.7R and γ_e = 1.3 ± 0.4. This indicates that the total heat capacity of the core is one-quarter that of the entire Earth.     

On time-step in structural seismic response analysis under ground displacement/acceleration

There are two models in use today to analyze structural responses when subjected to earthquake ground motions,the Displacement Input Model(DIM)and the Acceleration Input Model(AIM).The time steps used in direct integration methods for these models are analyzed to examine the suitability of DIM.Numerical results are presented and show that the time-step for DIM is about the same as for AIM,and achieves the same accuracy.This is contrary to previous research that reported that there are several sources of ...     

Watershed structural influences on the distributions of stream network water and solute travel times under baseflow conditions

Watershed structure influences the timing, magnitude, and spatial location of water and solute entry to stream networks. In turn, stream reach transport velocities and stream network geometry (travel distances) further influence the timing of export from watersheds. Here, we examine how watershed and stream network organization can affect travel times of water from delivery to the stream network to arrival at the watershed outlet. We analysed watershed structure and network geometry and quantified the relationship between stream discharge and solute velocity across six study watersheds (11.4 to 62.8 km²) located in the Sawtooth Mountains of central Idaho, USA. Based on these analyses, we developed stream network travel time functions for each watershed. We found that watershed structure, stream network geometry, and the variable magnitude of inputs across the network can have a pronounced affect on water travel distances and velocities within a stream network. Accordingly, a sample taken at the watershed outlet is composed of water and solutes sourced from across the watershed that experienced a range of travel times in the stream network. We suggest that understanding and quantifying stream network travel time distributions are valuable for deconvolving signals observed at watershed outlets into their spatial and temporal sources, and separating terrestrial and in‐channel hydrological, biogeochemical, and ecological influences on in‐stream observations. Copyright © 2016 John Wiley & Sons, Ltd.     

地震作用下陈庄黄土-泥岩接触面滑坡失稳机理及稳定性研究

以甘肃礼县陈庄黄土-泥岩接触面滑坡为研究对象,在对该滑坡的地震地质环境、基本特征等调查的基础上,运用数值分析对陈庄黄土-泥岩接触面滑坡在各人工计算场地基岩地震动时程作用下的失稳机理及稳定性进行动态模拟研究。结果表明,陈庄滑坡在地震诱发下变形破坏模式为受拉和受剪的复合破坏模式。失稳机理过程可概括为：地震作用→底部岩体受张拉→潜在滑面主滑段上部剪应力增大→剪应变集中带出现→剪应变集中带延伸扩展贯通→滑坡失稳;滑坡稳定性方面,随着输入地震动的增大,陈庄黄土-泥岩接触面滑坡稳定性降低,其中在50年超越概率2%的基岩地震动时程作用下滑坡处于不稳定状态。     

An error analysis of truncated starting conditions in step-by-step time integration: Consequences for structural dynamics

Most of the step-by-step time integration algorithms for structural dynamics require an initial acceleration vector to be specified, in addition to displacement and velocity vectors. A consistent initial acceleration vector may be calculated by solving the equations of motion at the initial time, while a truncated initial acceleration vector is obtained by setting the acceleration values to zero. Although the truncated starting procedure decreases computational effort, it is shown to affect accuracy adversely. For the structural dynamics algorithms considered herein, the rate at which the numerical solution converges to the exact solution is O(Δt) when the truncated starting procedure is used, compared to O(Δt²) when consistent initial acceleration values are used.