三峡工程永久船闸边坡岩体卸荷特性

从地貌学角度,分析了三峡工程永久船闸边坡岩体的自然及人为卸荷特性,指出了地表侵蚀、河流下切、开挖船闸等自然及人为地貌过程诱发了岩体的基本卸荷过程,构筑了一个三峡工程永久船闸边坡岩体卸荷特性的宏观模式。实地调砥及数值计算成果均表明,地貌分析法在分析实际岩体工程中,岩体卸荷特性方面具有较强的应用价值。     

90年代世界贸易发展及空间格局变化的新特点

在世界贸易组织、日趋强烈的开放的区域主义倾向、跨国公司强劲的直接投资影响下，世界贸易正在经历着巨大变化，处在一个新的转换时期。本文从影响当今世界贸易发展的多重因素分析，揭示90年代世界贸易增长、内容结构以及空间格局发展变化的新特征，并展望世界贸易的未来发展。     

P-SH conversions in a flat-layered medium with anisotropy of arbitrary orientation

P-SH conversion is commonly observed in teleseismic P waves, and is often attributed to dipping interfaces beneath the receiver. Our modelling suggests an alternative explanation in terms of flat-layered anisotropy. We use reflectivity techniques to compute three-component synthetic seismograms in a 1-D anisotropic layered medium. For each layer of the medium, we prescribe values of seismic velocities and hexagonally symmetric anisotropy about a common symmetry axis of arbitrary orientation. A compressional wave in an anisotropic velocity structure suffers conversion to both SV -and SH -polarized shear waves, unless the axis of symmetry is everywhere vertical or the wave travels parallel to all symmetry axes. The P-SV conversion forms the basis of the widely used 'receiver function' technique. The P-SH conversion occurs at interfaces where one or both layers are anisotropic. A tilted axis of symmetry and a dipping interface in isotropic media produce similar amplitudes of both direct ( P ) and converted ( Ps ) phases, leaving the backazimuth variation of the P-Ps delay as the main discriminant. Seismic anisotropy with a tilted symmetry axis leads to complex synthetic seismograms in velocity models composed of just a few flat homogeneous layers. It is possible therefore to model observations of P coda with prominent transverse components with relatively simple 1-D velocity structures. Successful retrieval of salient model characteristics appears possible using multiple realizations of a genetic-algorithm (GA) inversion of P coda from several backazimuths. Using GA inversion, we determine that six P coda recorded at station ARU in central Russia are consistent with models that possess strong (> 10 per cent) anisotropy in the top 5 km and between 30 and 43 km depth. The symmetry axes are tilted, and appear aligned with the seismic anisotropy orientation in the mantle under ARU suggested by SKS splitting.     

Ccte d'Ivoire-Ghana margin: seismic imaging of passive rifted crust adjacent to a transform continental margin

During May 1990 and January-February 1991, an extensive geophysical data set was collected over the Côte d'Ivoire-Ghana continental margin, located along the equatorial coast of West Africa. The Ghana margin is a transform continental margin running subparallel to the Romanche Fracture Zone and its associated marginal ridge—the Côte d'Ivoire-Ghana Ridge. From this data set, an explosive refraction line running ∼ 150 km, ENE-WSW between 3°55'N, 3°21'W and 4°23'N, 2°4'W, has been modelled together with wide-angle airgun profiles, and seismic reflection and gravity data. This study is centred on the Côte d'Ivoire Basin located just to the north of the Côte d'Ivoire-Ghana Ridge, where bathymetric data suggest that a component of normal rifting occurred, rather than the transform motion observed along the majority of the equatorial West African margin.
Traveltime and amplitude modelling of the ocean-bottom seismometer data shows that the continental Moho beneath the margin rises in an oceanward direction, from ∼ 24 km below sea level to ∼ 17 km. In the centre of the line where the crust thins most rapidly, there exists a region of anomalously high velocity at the base of the crust, reaching some 8 km in thickness. This higher-velocity region is thought to represent an area of localized underplating related to rifting. Modelling of marine gravity data, collected coincident with the seismic line, has been used to test the best-fitting seismic model. This modelling has shown that the observed free-air anomaly is dominated by the effects of crustal thickness, and that a region of higher density is required at the base of the crust to fit the observed data. This higher-density region is consistent in size and location with the high velocities required to fit the seismic data.     

以单位为基础的中国城市内部生活空间结构─兰州市的实证研究

本文着眼于中国城市居民生活的最基本组织─单位,通过考察其形成与作用、日常生活类型及空间分布特征等,得出中国城市的内部生活空间结构由三层次构成:(1)由在世界各种城市地域组织中独具一格的单位构成的基础生活圈;(2)同质单位为主形成的低级生活圈;(3)以区为基础的高级生活圈。这种独特的生活空间结构是在社会主义计划城市下行政管理和生活居住规划的双重影响下形成的。     

乌鲁木齐河源1号冰川积累区透底冰芯地层及冰结构分析

对乌鲁木齐河源１号冰川积累区一支深达９１．６４ｍ的透底冰芯进行了详细的层位及冰结构分析，结果表明，在２０ｍ深度以内，很好地保存了原始沉积的特征，但在７０￣８０ｍ深处还发现小密度的乳白色冰占优势的冰层，可能形成于小冰期，中层具有动力变质及再结晶作用共存及反复消长的结构特征（冰晶尺寸、气泡），未见单极大型组构，但出现弱竖环形组构，底层出现弱宝石状的多极大组构。     

岩体结构统计均质区的划分

本文介绍由Ｍｉｌｌｅｒ提出的基本概率统计理论的关联表分析，结合施密特投影图研究岩体统计均质区的划分方法。对该法进行了适当的修改，编写了相应的计算机程序。并对三峡永久船闸地区的岩体结构，进行了岩体结构统计均质区的划分，获得了良好的效果。     

渗流场反分析及其在多孔介质中的应用

本文讨论了复杂地质环境中渗流场的反分析问题，利用地下水流数值模拟结合最优化技术，通过对地下渗流场的模拟和寻优，求得描述地下含水介质非稳定渗流场的重要参位──渗透系数和给水度的模型解，并应用于各向同性的多孔介质渗流场反分析实例中。