土层剪切波速不确定性对场地刚性判断的影响

岩土工程中的不确定性是工程风险的重要来源。在我国7个主要地区的20个工程场地上开展了国内外首次大范围现场剪切波速不确定性专项试验,共由47家单位用11种工程常用仪器采用单孔法完成,获取了600组土层剪切波速Vs实测数据。依据实测结果拟合了场地时间平均剪切波速Vs, z的变异系数COV与计算深度Z的对应公式,揭示了土层剪切波速不确定性对场地刚性判断的影响,进而分析了我国场地分类的可能潜在误判区域。结论如下：在目前我国现场剪切波速测试水平下,Vs, z的变异系数与深度负相关——在近地表处达到极大值15%,并随着深度增加明显减小;地表至10 m深度区间内,Vs, z的变异系数迅速减小;10～20 m深度区间内,Vs, z的变异系数减小趋势变缓;超过20 m深度后,Vs, z的变异系数小于5%且基本不变;我国III、IV类场地分类采用的等效剪切波速Vse和欧美场地分类指标Vs, 30的变异系数基本相等;依据我国建筑抗震设计规范GB50011－2010,对I类场地以及覆盖层厚度小于5 m或等效剪切波速接近500 m/s的II类场地分类时需考虑剪切波速不确定性的潜在影响,其他类型的II类场地、III类和IV类场地在分类时基本可忽略其影响。     

Evaluation of Strong Motion Acceleration for Embankment Dam Design Considering Local Seismotectonics

A probabilistic method is used to evaluate the seismichazard of Adassiya dam site on the Yarmouk river in Jordan. A line source model developedby McGuire (1978) is used in this study. An updated earthquake catalogue coveringthe period from 1 A.D. to 1996 A.D. is used for this purpose. This catalogue includesall earthquakes that occurred in Jordan and adjacent areas, more specifically between latitudes27.0°–35.5°N and longitudes 32.0°–39.0°E.Nine distinct seismic sources of potential seismic activitiesare identified. The seismic hazard parameters are determined using the method suggested by Kijko and Sellevoll (1989).The Peak Ground Acceleration (PGA) is selected as a measure of ground motion severity. Esteva (1974) attenuation relationship is used in evaluating PGA values at each dam site. Analysis is carried out for 50%, 90%, and 95% probability that is not being exceeded in a life time of 50, 100, and 200 years.Results of analysis indicate that PGA values at the dam site are as follows:[] Operating Basis Earthquake (OBE) (50% probabilityof non-exceedance for a design life of 100 years – corresponding to a return period of 145 years) is 133.6 cm/sec².[] An earthquake with 90% probability of non-exceedancefor a design life of 50 years – corresponding to a return period of 475 years is 214.9 cm/sec².[] Maximum Credible Earthquake (MCE) (Return period of900 years) is 283.0 cm/sec².Strong motion acceleration time history of these earthquakes are givenbased on strong motion records of the November 1995 Gulf of Aqaba earthquake.Local site effect analysis for Adassiya Dam site using SHAKE program showed no amplification. Normalized site-specific acceleration response spectra for OBE and MCE design earthquakes is also given.     

Site effects in Mexico City urban zone. A complementary study

Site effects are a major factor affecting seismic risk at Mexico City conurbation and have been carefully studied. However, most of the studies and instrumentation concentrate in Mexico City. We present an evaluation of site effects in the counties of Estado de Mexico, to the North of Mexico City, that have been incorporated into Mexico City conurbation. We measured microtremors at 67 points and operated a temporal digital seismograph network. Our results allow us to extend the dominant period map of Mexico City to the heavily populated and industrialized counties of Estado de Mexico. Additionally, we propose a map of maximum relative amplification. Both maps are consistent with local geology, and could be useful for microzonation of this region.     

河南渑池仰韶人遗址区黄土冲沟阶地的释光测年研究

地貌变迁与古人类活动的关系一直是地理学研究的一个重要科学问题。仰韶文化是黄河流域最为重要的新石器人类 文明之一，文章以河南渑池仰韶遗址区内西沟冲沟为研究对象，尝试建立仰韶人类活动与遗址区内冲沟地貌形成的先后关 系。渑池仰韶遗址区地处黄土高原东南缘黄土堆积区，文章利用释光测年方法测定了西沟冲沟阶地上覆堆积黄土的年代， 粗略重建了阶地形成的时间为大约距今3万年和12万年前，分别对应深海氧同位素（MIS） 3阶段和5阶段。而该时期渑池 仰韶区域尚无古人类活动记录，所以释光测年结果证明仰韶遗址区内的冲沟完全是自然成因的，与遗址区仰韶人的地表活 动无关。     

云南的圣境及其在环境和生物多样性保护中的意义

圣境是由于传统的信仰文化的原因而建立和被保护的一类特殊自然－人文景观单元，对圣境的起源、分类在云南的分布和数目、生态价值和其它特征进行了描述和举例分析，提出了传统信仰文化和将乡土保护体系运用于农村生态恢复和生态多样性管理的潜在价值。以及将其纳入现代保护和开发项目的必要性。     

Analysis on the Regional Features of Coda Attenuation Before and After the 1992 Qina (M_S= 5.4, 5.1) Earthquakes in WYEPSA

Using the theoretical model of coda scattering from local earthquakes, we have studied the features of time-space variations of the attenuation rate β of coda amplitude and coda Qc-1 values before and after the Qina earthquakes (MS5.4 and MS5.1) in Dec. 1992 in West Yunnan Earthquake Prediction Study Area (WYEPSA). The study results show that the attenuation rate of coda amplitude has remarkable regional inhomogeneity in the near-field (△ <50 km) around the main shock: β = 0.0076 s-1 and Qc-1 = 0.0056 during the main shock while (3 = 0.0209 s-1 and Qc-1 = 0.0153 during the aftershock. The Qc-1 value shows an approximate 3-foid variation before and after the main shock. We have also obtained the regional averages of β = 0.0235 s-1 and Qc-1 = 0.0153, which show that the coda attenuation in surrounding areas (△ > 50 km) far away from the epicenter of the main shock did not change much before and after the main shock. The evolution of Qc-1 values of the main seismic sequence with time has passed throug     

跨入新世纪 迎接新挑战

本文分析了21世纪铀矿地质科研面临的新形势，提出今后工作的总体方针是认真贯彻中央精神，具体落实中核集团提出的目标任务，在成矿理论的创新与发展，传统与非传统矿产资源的勘查与开发利用，矿业开发与环境保护的协调发展等研究领域有新的突破。文章强调了大规模成矿作用及大型矿集区预测研究的重要性，认为应加强学科交叉和学术交流活动，争取良好的政策环境，保持必要的投资强度，培养和造就一批年轻的技术骨干和学科带头人，以崭新的姿态迎接21世纪的挑战。     

沉管灌注桩及打入式桩成桩前后场地类别的测试与分析

本文讨论了沉管灌注桩及打入式桩对场地类别的影响和减轻震害的机理，通过对淮阴工[学院主楼地基在成桩前后的建筑场地的剪切波速对比测试，作者发现沉管灌注桩及打入式桩有改变地类别的可能，最后建议《规范》^[1]应增加对采用桩基础的建筑（特别是打桩较密的高层建筑）在打桩后应再次进行剪切波速测试并对场地类别的重新判定等内容，从提供工程设计的经济效益和社会效益。