煤田采空区对地面地震动的影响

研究了煤田采空区对地面地震动的影响以及采空巷道的动应力分布。采空巷道用地表下圆孔来近似模拟,入射波场为造成较大震害的SH波。该问题采用镜像法求解,利用波函数展开和内域型Graf加法公式将解答归结为一组无穷代数方程组的求解,截断该无穷代数方程组可求得该问题的数值结果。最后,通过算例考虑了圆孔的动应力集中和地表动位移。结果表明,圆孔的动应力集中和地表的位移取决于入射波频率、角度和圆孔半径、埋深。该研究结果为煤田采空区的地震安全工作提供有益的参考。

工程结构场地地震动特征的研究理论和计算分析

本文介绍了一维单元波速分层模型分析垂直入射体波从基岩面地表的传播及地面地震动，场地特征，研究了有关问题，并实现了计算机编程和计算模拟分析，根据某高层建筑物场上地土层钻探结果及其基岩地震危险性，运用该程序对其他地面地震动进行了分析评价，该方法及程序可为规范要求的时程分析法提供合理的人工地震波输入，对场地地震波性评估，抗震设计有较大的应用价值。

实际地形对2010年玉树MS7.1地震动力学破裂过程及地震动特征的影响

基于震源动力学模型,采用曲线网格有限差分法模拟了水平自由地表及实际地形条件下2010年玉树MS7.1地震的震源破裂过程及相应的地面地震动,获取了断层面上的破裂传播过程、最终滑移量分布及峰值地面速度分布,讨论了实际地形对玉树地震破裂过程及相应地震动的影响。基于本文设定的动力学模型,模拟结果显示:断层面上的高应力降是玉树地震出现超剪切破裂传播现象的主要原因;计算区域的实际地形阻碍了由自由地表引起的超剪切破裂的产生,对断层面滑移量的分布特征及滑动速率影响较大,进而在一定程度上降低了地震动峰值,同时对地震动的分布特征产生影响,且地震动平行断层面的水平分量相对受影响更大。

基于强震记录的核电厂抗震标准反应谱研究

依据基岩场地上的汶川地震强震记录,分析了地震动地面峰值和核电站抗震标准反应谱的特性,证明了在推导和使用标准反应谱时所考虑的地面峰值加速度与地面峰值速度之比(PGA/PGV)受地面峰值加速度和震中距的影响,将对标准反应谱形状产生明显的影响.另外还发现了基岩场地的竖向峰值加速度可能要远比通常认为水平向峰值加速度的2/3大.通过对比汶川地震强震记录的伪速度谱和规范给出的标准反应谱,发现规范中的标准反应谱在长周期段偏小.最后采用两种新的拟合反应谱的方法,不仅改变了以往先确定控制点的做法,而且很好地反映了均值加标准差反应谱.

Safety Aspects of Sustainable Storage Dams and Earthquake Safety of Existing Dams

The basic element in any sustainable dam project is safety, which includes the following safety elements： O structural safety, dam safety monitoring, operational safety and maintenance, and emergency planning. Long-term safety primarily includes the analysis of all hazards affecting the project; that is, hazards from the natural environment, hazards from the man-made environment, and project-specific and site-specific hazards. The special features of the seismic safety of dams are discussed. Large dams were the first structures to be systematically designed against earthquakes, starting in the 1930s. How- ever, the seismic safety of older dams is unknown, as most were designed using seismic design criteria and methods of dynamic analysis that are considered obsolete today. Therefore, we need to reevaluate the seismic safety of existing dams based on current state-of-the-art practices and rehabilitate deficient dams. For large dams, a site-specific seismic hazard analysis is usually recommended. Today, large dams and the safety-relevant elements used for controlling the reservoir after a strong earthquake must be able to withstand the ground motions of a safety evaluation earthquake. The ground motion parameters can be determined either by a probabilistic or a deterministic seismic hazard analysis. During strong earthquakes, inelastic deformations may occur in a dam; therefore, the seismic analysis has to be car- ried out in the time domain. Furthermore, earthquakes create multiple seismic hazards for dams such as ground shaking, fault movements, mass movements, and others. The ground motions needed by the dam engineer are not real earthquake ground motions but models of the ground motion, which allow the safe design of dams. It must also be kept in mind that darn safety evaluations must be carried out several times during the long life of large storage dams. These features are discussed in this paper.

Vertical-to-horizontal response spectral ratio for offshore ground motions:Analysis and simplified design equation

In order to study the differences in vertical component between onshore and offshore motions,the vertical-to-horizontal peak ground acceleration ratio(V/H PGA ratio) and vertical-to-horizontal response spectral ratio(V/H) were investigated using the ground motion recordings from the K-NET network and the seafloor earthquake measuring system(SEMS).The results indicate that the vertical component of offshore motions is lower than that of onshore motions.The V/H PGA ratio of acceleration time histories at offshore stations is about 50%of the ratio at onshore stations.The V/H for offshore ground motions is lower than that for onshore motions,especially for periods less than 0.8 s.Furthermore,based on the results in statistical analysis for offshore recordings in the K-NET,the simplified V/H design equations for offshore motions in minor and moderate earthquakes are proposed for seismic analysis of offshore structures.

Influence of site conditions on ground motion at far field loess sites during strong earthquake

Loess is widely distributed in China and the Loess Plateau is one of the major areas where strong earthquakes often take place. The seismic amplification effects were discovered in the Plateau during the Wenchuan Ms8.0 earthquake and some other strong events. Based on earth tremor observation, borehole exploration and site seismic response analysis, the site effects of topography of Loess Yuan on ground motion were investigated in details. The earth tremor investigation shows that predominant frequencies at the bottom sites of Loess Yuan are greater than those at the top obviously. The sites seismic response analysis shows that the Loess Yuan may amplify peak ground acceleration (PGA) by 1.44 2.0 times. Therefore, site effects of mountains and loess topography on ground motion should be taken account into in seismic design in loess regions.

GIS-based Evaluation on the Fault Motion-Induced Coseismic Landslides

Earthquake-induced potential landslides are commonly estimated using landslide susceptibility maps. Nevertheless, the fault location is not identified and the ground motion caused by it is unavailable in the map. Thus, potential coseismic landslides for a specific fault motion-induced earthquake could not be predicted using the map. It is meaningful to incorporate the fault location and ground motion characteristics into the landslide predication model. A new method for a specific fault motion-induced coseismic landslide prediction model using GIS （Geographic Information System） is proposed herein. Location of mountain ridges, slope gradients over 45~, PVGA （Peak Vertical Ground Accelerations） exceeded o.15 g, and PHGA （Peak Horizontal Ground Accelerations） exceeded o.25 g of slope units were representing locations that initiated landslides during the 1999 Chi-Chi earthquake in Taiwan. These coseismic landslide characteristics were used to identify areas where landslides occurred during Meishan fault motion-induced strong ground motions in Chiayi County in Taiwan. The strong ground motion （over 8 Gal in the database, 1 Gal = 0.0l m/s2, and 1 g = 981 GaD characteristics were evaluated by the fault length, site distance to the fault, and topography, and their attenuation relations are presented in GIS. The results of the analysis show that coseismic landslide areas could be identified promptly using GIS. The earthquake intensity and focus depthhave visible effects on ground motion. The shallower the focus depth, the larger the magnitude increase of the landslides. The GIS-based landslide predication method is valuable combining the geomorphic characteristics and ground motion attenuation relationships for a potential region landslide hazard assessment and in disaster mitigation planning.

Effect of Shear Wave Velocity on the Ground Motion Parameters of Site Surface

Based on the data from typical sites in the Jianghuai region,many kinds of soil layer seismic response are modeled by increasing and decreasing the measured values of shear velocity to a certain scale. The seismic response of soil layer sites are calculated using the one-dimensional equivalent linear method in the frequency domain by choosing the Taft,Kobe and El-centro records as the ground motion input. The results show that the impact of shear velocity variability on the surface ground motion is in relation to the soil layer structure and ground motion input parameters such as amplitude and spectral characteristic. With the increase of shear velocity,the PGA( peak ground acceleration)on the surface of site will increase,however,the characteristic period of the acceleration response spectra is decreasing.

Analysis of Ground Motion Attenuation Characterization for Moderate Earthquakes in the Sichuan-Yunnan Region

The ground motion attenuation models for PGA,PGV and response spectrum at rock sites and soils sites are derived separately from the digital strong motion records of moderate earthquakes in the Sichuan-Yunnan region after 2007. By comparison with Yu Yanxiangs attenuation model for rock sites in western China,reliability of the model is verified for moderate earthquake. According to the distribution of strong motion data against magnitude and epicentral distance,the applicability and reliability of the results in this paper are discussed.

Intensity measures for seismic liquefaction hazard evaluation of sloping site

This work investigates the correlation between a large number of widely used ground motion intensity measures(IMs) and the corresponding liquefaction potential of a soil deposit during earthquake loading. In order to accomplish this purpose the seismic responses of 32 sloping liquefiable site models consisting of layered cohesionless soil were subjected to 139 earthquake ground motions. Two sets of ground motions, consisting of 80 ordinary records and 59 pulse-like near-fault records are used in the dynamic analyses. The liquefaction potential of the site is expressed in terms of the the mean pore pressure ratio, the maximum ground settlement, the maximum ground horizontal displacement and the maximum ground horizontal acceleration. For each individual accelerogram, the values of the aforementioned liquefaction potential measures are determined. Then, the correlation between the liquefaction potential measures and the IMs is evaluated. The results reveal that the velocity spectrum intensity(VSI) shows the strongest correlation with the liquefaction potential of sloping site. VSI is also proven to be a sufficient intensity measure with respect to earthquake magnitude and source-to-site distance, and has a good predictability, thus making it a prime candidate for the seismic liquefaction hazard evaluation.

Dynamic response characteristics of super high-rise buildings subjected to long-period ground motions

Spectrum characteristics of different types of seismic waves and dynamic response characteristics of super high-rise building structures under long-period ground motions were comparatively analyzed. First, the ground response wave （named LS-R wave） of a soft soil site with deep deposit, taking long-period bedrock seismic record as input, was calculated by wave propagation method. After that, a TOMAKOMAI station long-period seismic record from the Tokachi-Oki earthquake and conventional E1-Centro wave were also chosen. Spectrum characteristics of these waves were analyzed and compared. Then, a series of shaking table tests were performed on a 1：50 scale super high-rise structural model under these seismic waves. Furthermore, numerical simulation of the prototype structure under these excitations was conducted, and structure damages under different intensive ground motions were discussed. The results show that： 1） Spectrum characteristics of ground response wave are significantly influenced by soft soil site with deep deposit, and the predominant period has an increasing trend. 2） The maximum acceleration amplification factor of the structure under the TOM wave is two times that under the E1-Centro wave; while the maximum displacement response of the structure under the TOM wave is 4.4 times that under the E1-Centro wave. Long-period ground motions show greater influences on displacement responses than acceleration responses for super high-rise building structures. 3） Most inelastic damage occurs at the upper 1/3 part of the super high-rise building when subjected to long-period ground motions.

Seismic Ground Motion Zoning Maps of the Pangxi Region

The seismotectonic environment and seismic activity in Southwest China region were studied based on new data and new results obtained during the Eighth and Ninth Five-Year Plans, the seismic areas and zones and potential seismic source zones were determined, and the relation between seismic activity parameters and ground motion attenuation was determined. Finally the seismic ground motion zoning maps of the Pangxi region was compiled by using the multi-parameter and multi-scheme method.

Study on Site Specific Design Earthquake Ground Motion of Nuclear Power Plants in China

The main technical backgrounds and requirements are introduced with regard to earthquake ground motion design parameters in several domestic and American standards,codes and guides involved in the seismic analysis and design activities of nuclear power plants in China.Based on the research results from site seismic safety evaluation of domestic nuclear power plant projects in the last years,characteristics and differences of site specific design spectra are analyzed in comparison with standard response spectra,and the suitability of standard response spectra for domestic nuclear power plant projects is discussed.

Some Analyses on Effects of Site Classification on Ground Motion Characteristics in the Chi-Chi,Taiwan Earthquake

According to the epicenter distance and the site classification, the 404 groups of earthquake recordings of the main shock of the Chi-Chi, Taiwan China earthquake in 1999 are catalogued. Based on these data, we analyze the statistical features of duration, PGA, envelopes and the response spectra ratio of the horizontal and vertical components of the acceleration recordings. The results of these analyses show that the effect of site classification on the acceleration of various components is obvious; furthermore, fault direction also has certain effects on the characteristics of the horizontal components of ground motion. The detailed research results are as follows： （ 1 ） the duration of the horizontal components of acceleration records increases with the softening of the site; （2） the direction of fault slip has some effects on PGA＇s attenuation features; （3） the average envelopes of acceleration records at different distances and site dames are basically single peak functions of time and the envelopes of horizontal and vertical components of ground motion are obviously different; （4） with the same epicenter distance, EW/NS response spectrum ratios tend to approximate 1.0 as the site becomes softer and the period shorter. V/H response spectrum ratios in short periods （〈 0. 1s） increase with the softening of site, however, V/H ratios within the long-period range （ 〉 characteristic period） decrease with the softening of the site, and the decrease of V/EW ratio speeds up relatively.

Surface Soil Effects Studies Based on HN Ratios of Microtremors at Kingston Metropolitan Area, Jamaica

The authors performed single mobile microtremor measurements at 218 sites at KMA （Kingston Metropolitan Area） with the objective of estimating the amplification effects due to the earthquake ground motion on the surface geology. The Fourier transform was applied to the most stationary parts of the triaxial wave motion recordings for each individual site and applied the traditional Nakamura technique, namely, the horizontal to vertical spectral ratio （H/V） to retrieve the predominant shear wave period of vibration of the soil profiles above the bedrock. The results yield predominant long periods of about 3.0-4.0 s in the port area and the waterfront, 1.0-2.0 s in the central part of Kingston, 0.3-1.0 s in Portmore and very stiff soil conditions in the surrounding area of the city. The results coincide fairly well with previous geological studies in the region, geotechnical data in boreholes, gravimetric measurements and strong motion recordings, suggesting a high degree of amplification of ground motion in the whole period range of engineering interest. Additionally, the authors obtained the liquefaction vulnerability factor Kg proposed by Nakamura based on the H/V ratio of microtremors. The results suggest that the port area, the waterfront and the Port Royal are highly susceptible to liquefaction. Finally, the authors obtained fundamental periods of vibration based on microtremor measurements on the roof and the basement of four important buildings in the KMA and indicated future lines of research employing ambient noise measurements on structures.

Preliminary Study on the Correlation between Intensity Isoseismals and the Seismic Source Process of the Wenchuan Earthquake in Sichuan,China

The M_S8.0 Wenchuan earthquake in Sichuan caused heavy casualties and serious economic loss because of damage to engineering structures in high earthquake intensity regions. Earthquake intensity, especially in the near source region, as a macroscopic description of distribution of strong ground motions certain correlations with the earthquake source process, such as rupture directivity and the hanging-wall effect of the near-fault ground motions of this earthquake. In this article some qualitative analyses are carried out. The conclusion of this study may be useful for emergence response and rescue after earthquakes, when the strong ground motion recordings and the intensity distribution are not available immediately.

Simulation of Sliding Failure Occurred at Highway Embankment in 2011 Great East Japan Earthquake

In the 2011 Great East Japan Earthquake, the highway embankments were almost less damaged comparing with the past earthquakes in Japan. But the only one embankment close to the Naka Interchange at Joban Highway was damaged a little severely and remarkably because of two interesting phenomena. One phenomenon is the toe-sliding failure observed at the shallow soft base ground and the other one is one-side slope sliding failure. It can be seen that the increase in the degree of saturation at embankment body or the direction of the ground motion or the interaction between the strength of the base ground and the embankment body are involved in the stability of the embankment by modifying the phenomenon by analytical approach such as circular sliding method and dynamic response analysis. Through this research, some important lessons can be obtained for future seismic countermeasure of embankments.

Study on the Relationship of Seismic Design Ground Motion at Different Fortification Levels in the Xinjiang Region

The seismic risk analysis results of 79 cities in Xinjiang are presented, and the bedrock peak ground accelerations under three seismic levels and their ratios are discussed. Then, the relationship between earthquake environments and the seismic risk analysis results of different exceeding probabilities are researched. The results show that minor and major earthquake motion parameters calculated from moderate earthquakes do not have a consistent probability and the ratio of bedrock peak accelerations under different exceedance probabilities are dosdy correlated with earthquake environments.

Discussion on the Relationship between “Anti-great Earthquakes” and Ground Motion with a Low Probability of Exceedance

In this paper we discuss the differences and relationship between"great earthquakes",rare ground motion,and very rare ground motion.Taking the Beichuan-Yingxiu potential seismic source zone in Longmenshan seismic belt as an example,we revealed the relationship between the effects of"great earthquakes"and rare ground and very rare ground motion.After pointing out scientific and technical problems in the current seismic fortification system,we suggest that very rare ground motion should be considered if we want to deduce the potential hazard of great earthquakes in the future.