河北文安5.1级地震首都圈实时强震动台网加速度记录分析

通过分析首都圈实时强震动台网对文安5.1级地震的强震动记录及其加速度等值线图的对比,结果表明:(1)仪器记录峰值加速度衰减特性可以反映地震宏观特征;(2)仪器记录峰值加速度衰减关系可以作为基岩水平理论衰减关系峰值加速度的一种标定方法;(3)这次地震为我们今后进行强震动观测提供了重要的经验启示及改进方向.     

Effect of mineral reactions on the hydraulic properties of unsaturated soils: Model development and application

The selective radius shift model was used to relate changes in mineral volume due to precipitation/dissolution reactions to changes in hydraulic properties affecting flow in porous media. The model accounts for (i) precipitation/dissolution taking place only in the water-filled part of the pore space and further that (ii) the amount of mineral precipitation/dissolution within a pore depends on the local pore volume. The pore bundle concept was used to connect pore-scale changes to macroscopic soil hydraulic properties. Precipitation/dissolution induces changes in the pore radii of water-filled pores and, consequently, in the effective porosity. In a time step of the numerical model, mineral reactions lead to a discontinuous pore-size distribution because only the water-filled pores are affected. The pore-size distribution is converted back to a soil moisture characteristic function to which a new water retention curve is fitted under physically plausible constraints. The model equations were derived for the commonly used van Genuchten/Mualem hydraulic properties. Together with a mixed-form solution of Richards’ equation for aqueous phase flow, the model was implemented into the geochemical modelling framework PHREEQC, thereby making available PHREEQC’s comprehensive geochemical reactions. Example applications include kinetic halite dissolution and calcite precipitation as a consequence of cation exchange. These applications showed marked changes in the soil’s hydraulic properties due to mineral precipitation/dissolution and the dependency of these changes on water contents. The simulations also revealed the strong influence of the degree of saturation on the development of the saturated hydraulic conductivity through its quadratic dependency on the van Genuchten parameter α. Furthermore, it was shown that the unsaturated hydraulic conductivity at fixed reduced water content can even increase during precipitation due to changes in the pore-size distribution.     

山西原平4．2级地震山西数字强震动记录分析

对2009年3月28日山西原平4．2级地震山西数字强震动台网7个台的地震加速度记录进行了处理和分析,包括对加速度波形数据的基线校正、滤波、水平分向矢量合成以及部分台站速度计算（包括水平向速度矢量合成）和加速度付氏谱、反应谱计算。结果表明：记录的最大单分向（水平）加速度峰值为27．5cm／s^2,水平合成最大加速度PGAn为28．5cm／s^2,其折合地震烈度为5度。多数台站的垂直向加速度峰值大约为水平向的1／2。最大速度峰值PGVH为0．51cm／s。原平台加速度记录的谱分析表明,对于4～5级这样强度的地震,因为震源本身产生的地震波中的长周期成分很少,所以,厚覆盖土层对长周期地震波的影响在工程的意义上可以忽略。     

Using microtremors for microseismic zonation in Cairo’s crowded, urban areas

In order to determine the fundamental period of soil vibrations in Cairo, 174 microtremors stations, in conjunction with mobile accelerographs, were used. The result was a collection of long-period microtremors and ambient noise arising from cultural disturbances. The Nile Valley shows some fixed peaks at 2.5–3.5 Hz at the center of the basin, while the Nile’s surrounding area shows a fundamental peak of 4–5 Hz, leaving a 5–7-Hz resonance peak for the sand-like, gravelly soil from Abbasiya to the airport. A frequency-dependent soil amplification map is drawn, which includes seismic microzonation maps for Cairo. Based on the above, a maximum acceleration map for two important earthquakes affecting Egypt in the last century is produced (Faiyum, 1992, and Aqaba, 1995).     

地磁低点位移与地磁场等效电流体系关系的初步研究

利用地磁内外源场分离的方法,反演得到了1997年11月8日玛尼地震和1998年１月10日张北地震前地下和空间等效电流体系的演化图象,并分析研究了地磁低点位移出现前后等效电流体系变化特征．结果表明,内、外场等效电流体系的变化与地震ldquo;低点位移rdquo;异常现象有着内在的联系,等效电流体系变化可能是地磁低点位移异常现象产生的原因之一。随着我国地磁台站的加密建设,势必可以得到更为精确的地磁场等效电流体系的演化特征,更有利于地震预测的研究。      

Nonlinear response analyses of a soil–structure interaction system using transformed energy transmitting boundary in the time domain

The energy transmitting boundary used in programs such as FLUSH and ALUSH is a very accurate and useful technique for the earthquake response analysis of soil–structure interaction systems. However, it is applicable only to linear analyses or equivalent linear analyses, because it can be calculated only in the frequency domain. The author has proposed methods for transforming frequency-dependent impedance into the time domain. In this paper, an earthquake response analysis method for a soil–structure interaction system, using the energy transmitting boundary in the time domain, is proposed. First, the transform of the transmitting boundary matrices to the time domain using the methods proposed by the author is studied. Then, linear and nonlinear time history earthquake response analyses using the boundary are performed. Through these studies, the validity and efficiency of the proposed methods are confirmed.     

基于BP神经网络模型的多层砖房震害预测方法

针对传统的基于地震烈度的建筑物震害预测方法的不足,本文以地震动峰值加速度作为建筑物震害预测的地震动指标,结合几次大地震中多层砖房的震害实例,提出了一种基于BP神经网络模型的建筑物震害预测方法,模型的输入为反映结构抗震性能的各类物理参数,输出为给定地震动峰值加速度下建筑物破坏状态的概率。研究表明:基于BP网络模型的多层砖房的震害预测结果与震害实例的实际情况比较吻合,本文的思路和方法可推广于其他不同类型的建筑结构的震害预测。     

1679年三河-平谷8级地震近断层强地震动的有限元模拟

文中通过收集整理三河-平谷8级地震的历史记录、野外地质调查和区域地震等资料,建立了该地震的震源模型;以穿过研究区的12条测线和区域第四纪、新近纪、古近纪沉积等厚度图等资料为基础,建立了北京地区的传播介质模型;利用哈尔滨工程力学研究所的近断层强地震动有限元程序和40节点的高性能并行计算机计算了北京地区震后60s内地表各点的地震动速度时程和峰值速度。为检验模拟结果的质量,我们取2排测点的速度时程和水平向峰值速度等值线图进行了分析,发现计算结果与历史地震记录及实际地震观测资料吻合良好,说明了我们的模拟结果的可信性和模拟方法的客观性     

Synthesis of accelerograms compatible with the Chinese GB 50011-2001 design spectrum via harmonic wavelets： artificial and historic records

A versatile approach is employed to generate artificial accelerograms which satisfy the compatibility criteria prescribed by the Chinese aseismic code provisions GB 50011-2001. In particular, a frequency dependent peak factor derived by means of appropriate Monte Carlo analyses is introduced to relate the GB 50011 -2001 design spectrum to a parametrically defined evolutionary power spectrum (EPS). Special attention is given to the definition of the frequency content of the EPS in order to accommodate the mathematical form of the aforementioned design spectrum. Further, a one-to-one relationship is established between the parameter controlling the time-varying intensity of the EPS and the effective strong ground motion duration. Subsequently, an efficient auto-regressive moving-average (ARMA) filtering technique is utilized to generate ensembles of non-stationary artificial accelerograms whose average response spectrum is in a close agreement with the considered design spectrum. Furthermore, a harmonic wavelet based iterative scheme is adopted to modify these artificial signals so that a close matching of the signals' response spectra with the GB 50011-2001 design spectrum is achieved on an individual basis. This is also done for field recorded accelerograms pertaining to the May, 2008 Wenchuan seismic event. In the process, zero-phase high-pass filtering is performed to accomplish proper baseline correction of the acquired spectrum compatible artificial and field accelerograms. Numerical results are given in a tabulated format to expedite their use in practice.     

岩石破裂电磁辐射频率与岩石属性参数的关系

为进一步明确岩石破裂电磁辐射频率特征,基于岩石破裂电磁辐射是由岩石破裂时传播裂纹引起原子扰动产生的假说, 通过断裂力学理论中小范围屈服条件下张开位移法计算岩石破裂时的裂纹宽度,由单脉冲电磁辐射频率与裂纹宽度之间的关系,研究电磁辐射频率与岩石属性参数之间的关系,并给出了它们之间的关系表达式;单独讨论了不同属性参数对电磁辐射频率的影响.结果表明,电磁辐射频率随弹性模量增大而增大,随岩样尺寸和强度增大而减小,随泊松比的变化、岩石弹模的不同电磁辐射频率有变化;当弹模较小时,泊松比的影响也较小,而当弹模很大,即岩石刚度很大时,泊松比的增大会导致频率的增大;裂纹初始长度的变化受试件尺寸的影响,进而影响频率,当尺寸较大时,裂纹长度对频率影响较小,当尺寸较小时,频率随裂纹长度增大而增大.通过计算几种常见岩石破裂时电磁辐射频率值发现,岩石破裂时电磁辐射频率达到105 Hz量级,这与现有的实验结果相吻合.