宣城第四纪红色粘土剖面的发育特征

宣城第四纪红色粘土14层土体硅铝率、风化淋溶系数,以及阳离子交换量、盐基饱和 度和粘粒含量等风化、成土作用指标表明,该剖面各层次之间仅显示出一定程度沉积作用和成土作用的差别。它们是边沉积边成土作用的产物。上覆lm左右厚下蜀黄土,且由均质红土层、铁锰焦斑层和网纹层构成的宣城第四纪红色粘土应归属于埋藏类型古土壤。     

The gravitational attraction of any polygonally shaped vertical prism with inclined top and bottom faces

 A closed formula for computing the gravitational attraction of a general vertical prism with N+2 faces (N faces are vertical planes, the other two are the inclined top and bottom planes) in Cartesian coordinates is presented. In addition, the special case of a triangular prism is discussed. Algebraic differences and overlooked singularity conditions of a previously published formula of this computation (which was only for the triangular special case) were identified and are also presented. Received: 22 March 1999 / Accepted: 2 February 2000     

高频雷达在混凝土无损检测中的应用及关键技术

本文阐述了混凝土体无损检测的基本方法技术。将地质雷达方法引入该领域中,结合工程实例研究地质雷达在混凝土非破损检测中的应用效果。并针对实际问题,利用分形技术对雷达资料进行处理,以提取雷达高分辨率信息。     

Element geochemistry of weathering profile of dolomitite and its implications for the average chemical composition of the upper-continental crust--Case studies from the Xinpu profile,northern Guizhou Province,China

Geochemical behavior of chemical elements is studied in a dolomitite weathering profile in upland of karst terrain in northern Guizhou.Two stages can be recognized during the process of in situ weathering of dolomitite:the stage of sedentary accumulation of leaching residue of dolomitite and the stage of chemical weathering evolution of sedentary soil.Ni,Cr,Mo,W and Ti are the least mobile elements with reference to Al.The geochemical behavior of REE is similar to that observed in weathering of other types of rocks.Fractionation of REE is noticed during weathering,and the two layers of REE enrichments are thought to result from downward movement of the weathering front in response to changes in the environment.It is considered that the chemistry of the upper part of the profile,which was more intensively weathered,is representative of the mobile components of the upper curst at the time the dolomitite was formed,while the less weathered lower profile is chemically representative of the immobile constitution.Like glacial till and loess,the "insoluble" materials in carbonate rocks originating from chemical sedimentation may also provide valuable information about the average chemical composition of the upper continental crust.     

Sea-level changes, geoid and gravity anomalies due to Pleistocene deglaciation by means of multilayered, analytical Earth models

A new class of analytical, multilayered, viscoelastic Earth models based on PREM, with an incompressible, linear, viscoelastic Maxwell rheology, is applied to the modeling of global sea-level changes due to Pleistocene deglaciation. Until now, analytical schemes based on normal mode theory, have dealt with at most five layers, an elastic lithosphere, a three layered mantle including a transition zone, and a core (Spada et al., 1992. Geophys. J. Int. 109, 683–700). The novelty of our approach, used for the first time in sea-level studies, stands on an analytical scheme that can reproduce continuous elastic and rheological stratification when a sufficient number of layers is taken into account. We specifically assess the importance of our results for the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite mission. GOCE will resolve the gravity field with a spatial resolution (half-wavelength) of 75 km and amplitude of 1.5 mgal, with a uniform coverage over the Earth, including presently unsurveyed, remote areas. Our models lead to post-glacial rebound induced free air gravity anomalies of a few mgals peak-to-peak in the harmonic degree range l=80–200, which will be discernible by GOCE. This finding demonstrates that post-glacial rebound has a high frequency component in the gravity field that can in principle be resolved by high resolution gravity satellite missions. We show that post-glacial rebound can contribute a substantial fraction to present-day sea-level variations and point out that for the Mediterranean Sea they are of the same order of magnitude as those induced by tectonic processes.     

How to handle topography in practical geoid determination: three examples

 Three different methods of handling topography in geoid determination were investigated. The first two methods employ the residual terrain model (RTM) remove–restore technique, yielding the quasigeoid, whereas the third method uses the classical Helmert condensation method, yielding the geoid. All three methods were used with the geopotential model Earth Gravity Model (1996) (EGM96) as a reference, and the results were compared to precise global positioning system (GPS) levelling networks in Scandinavia. An investigation of the Helmert method, focusing on the different types of indirect effects and their effects on the geoid, was also carried out. The three different methods used produce almost identical results at the 5-cm level, when compared to the GPS levelling networks. However, small systematic differences existed. Received: 18 March 1999 / Accepted: 21 March 2000     

A synthetic Earth for use in geodesy

 A synthetic Earth and its gravity field that can be represented at different resolutions for testing and comparing existing and new methods used for global gravity-field determination are created. Both the boundary and boundary values of the gravity potential can be generated. The approach chosen also allows observables to be generated at aircraft flight height or at satellite altitude. The generation of the synthetic Earth shape (SES) and gravity-field quantities is based upon spherical harmonic expansions of the isostatically compensated equivalent rock topography and the EGM96 global geopotential model. Spherical harmonic models are developed for both the synthetic Earth topography (SET) and the synthetic Earth potential (SEP) up to degree and order 2160 corresponding to a 5′×5′ resolution. Various sets of SET, SES and SEP with boundary geometry and boundary values at different resolutions can be generated using low-pass filters applied to the expansions. The representation is achieved in point sets based upon refined triangulation of a octahedral geometry projected onto the chosen reference ellipsoid. The filter cut-offs relate to the sampling pattern in order to avoid aliasing effects. Examples of the SET and its gravity field are shown for a resolution with a Nyquist sampling rate of 8.27 degrees. Received: 6 August 1999 / Accepted: 26 April 2000     

正断层断距纵剖面图及其运动学:概念模型与地质实例

断距纵剖面图 （T H图）是指以断层的垂直断距为横轴、以地层或地质年龄为纵轴所绘制的随地层或地质年龄所变化的断距分布图。断距纵剖面图为确定正断层类型、断层形成时间和断层的纵向演化史提供了一个简单迅捷的工具。概念模型表明,断距纵剖面图可以明确无误地区分出简单后沉积型正断层、后沉积拱顶拉张型正断层、同沉积生长型正断层及其复合型正断层。简单后沉积型正断层的断距不随地层年龄的变化而变化, 其断距纵剖面图为一垂直线段。后沉积拱顶拉张型正断层的断距随地层年龄的增大而减小并趋向零值,同沉积生长型正断层的断距随地层年龄的增大而增大,复合型正断层则具其组合型断距纵剖面形态。除简单后沉积型正断层外,断距纵剖面图中的最大断距点代表了该断层的起始形成年代。     

藻类结皮自然恢复后抗风蚀特性研究

从风沙物理学的角度出发,通过风洞实验研究藻类结皮对起动风速、摩阻风速、空气动力学粗糙度等的影响,探讨未破坏藻类结皮和一定程度破坏后自然恢复藻类结皮抗土壤风蚀特性。实验结果表明:无论是完好结皮还是自然恢复后的结皮,都可以提高结皮的起动风速、摩阻风速和空气动力学粗糙度长度。结皮的起动风速大于17 m·s^-1,摩阻风速在0.62~1.21 m·s^-1之间,空气动力学粗糙度长度在0.03~0.13 cm之间。同时给出了摩阻风速和风速之间以及空气动力学粗糙度长度和摩阻风速之间的经验公式。     

A New Approach to Gravity Anomaly Separation: Differential Markov Random Field (DMRF)

In this paper the authors introduce a novel approach to stochastic image processing, denoted as Differential Markov Random Field (DMRF), which has been applied to gravity anomaly separation problems. The advantages of the method are that it introduces only little distortion into the shape of the original image and that it is not affected significantly by factors such as the overlap power spectra of regional and residual fields. Testing of the proposed meth using synthetic examples gave excellent results.