SH Wave Propagation in Viscoelastic Media

When comparing solutions for the propagation of SH waves in plane parallel layered elastic and viscoelastic (anelastic) media, one of the first things that becomes apparent is that in the elastic case the location of the saddle points required to obtain a high frequency approximation are located on the real p axis. This is true of the branch points also. In a viscoelastic medium this is not typical. The saddle point corresponding to an arrival lies in the first quadrant of the complex p-plane as do the branch points. Additionally, in the elastic case the saddle point and branch points lie on a straight line drawn through the origin (the positive real axis in the complex p-plane), while in the viscoelastic case this is generally not the case and the saddle point and branch points lie in such a manner as to indicate the degree of their complex values.In this paper simple SH reflected and transmitted particle displacement arrivals due to a point torque source at the surface in a viscoelastic medium composed of a layer over a half space will be considered. The path of steepest descent defining the saddle point in the first quadrant will be parameterized in terms of a real variable and the high frequency solutions and intermediate analytic results obtained will be used to formulate more specific constraints and observations regarding saddle point location relative to branch point locations in the complex p-plane.As saddle point determination for an arrival is, in general, the solution of a non-linear equation in two unknowns (the real and imaginary parts of the complex saddle point p ₀), which must be solved numerically, the use of analytical methods for investigating this problem type is somewhat limited.Numerical experimentation using well documented solution methods, such as Newton's method, was undertaken and some observations were made. Although fairly basic, they did provide for the design of algorithms for the computation of synthetic traces that displayed more efficient convergence and accuracy than those previously employed. This was the primary motivation for this work and the results from the SH problem may be used with minimal modifications to address the more complicated subject of coupled P-SV wave propagation in viscoelastic media.Another reason for revisiting a problem that has received some attention in the literature was to approach it in a fairly comprehensive manner so that a number of specific observations may be made regarding the location of the saddle point in the complex p-plane and to incorporate these into computer software. These have been found to result in more efficient algorithms for the SH wave propagation and a significant enhancement of the comparable software in the P-SV problem.     

基于拉格朗日插值法修正地形影响的分布式降水模型研究

降水量一直是进行水文分析计算的输入项，对其分布状况的模拟直接影响水文分析成果精度。降水中心位置及其中心降水量对暴雨分析尤为重要，而目前尚未见对降水中心位置方面的模型研究。在对目前国内外降水模型分析的基础上，根据天气系统降水如不受地形影响其降水量等值线在平面上的分布近似为一组同心椭圆这一原理，建立了一种能够模拟次降水过程的降水中心位置及其中心降水量的新型分布式降水数学模型，并对其进行地形影响因素修正。由于模型建立原理简单，易于实现对流域未设站研究点的实时降水量估计，同时由于模型能够指明降水中心位置及其中心降水量，因此在流域暴雨分析和洪水预报中具有实用价值。模型经实践检验具有较高精度。     

基于共反射点叠加的观测参数选择

在地震勘探数据处理中，通常采用的共中心点(CMP)叠加技术对于复杂的地质构造难以取得好的效果。若通过从道间距、覆盖次数等观测参数与目标层地层倾角、共反射点离散度的关系出发，并结合模型正演，对复杂构造地层的观测参数选取进行优化，使之能对目标层尤其是逆断层下降盘的阴影层段进行较充分的“照明”，即可得到共反射点叠加剖面，这对共反射点叠加是一项有益的研究。     

Curie Point Depths Beneath Precordillera Cuyana and Sierras Pampeanas Obtained from Spectral Analysis of Magnetic Anomalies

A gravity and magnetic survey has been carried out with the purpose of investigating geophysical features of the crusts beneath three geological provinces in western Argentina: Cuyo Precordillera, the Sierras Pampeanas of San Juan and La Rioja, and Famatina System, the results of which are displayed in three maps: Bouguer anomaly, total field magnetic anomaly and total field reduced to the pole.

The top and bottom boundaries of the magnetized crust were calculated from power-density spectra of the total-field anomalies from our terrestrial database in 90 2D windows. The depths obtained for the bottom of magnetized crust are assumed to correspond to Curie point depths. The values thus obtained for the Precordillera range between 29 and 40 km, whereas for the Sierras Pampeanas, in the Sierra de Pie de Palo, and other mountain chains along the Bermejo-Desaguadero lineament or Valle Fértil lineament, such depth ranges between 20 and 35 km. These results are consistent with Curie point depths determined on different continental regions in the world.

A map of regional heat flow has been prepared in the present work based on the depth of the Curie point isotherm, which shows that heat flow patterns in Precordillera are different from those found in Sierras Pampeanas.

A significant heat flow extending in Northeast-Southwest direction seems to be directly related to Juan Fernández Ridge trace.

The results of the present investigations also point out a possible relationship between the base of the magnetized crust and the boundary separating the brittle from the ductile crustal regime.     

Spatial variability and pattern analysis of soil properties in Dehui city, Jilin province

1IntroductionSoil nutrient, as the synthetic results under the influence of various anthropogenic activities and the factors such as climate and topography, etc., possesses certain spatial distribution characteristics, and certain structural and stochastic characteristics. The study of the differences existing in different parts of the region lays the foundation for adjusting all management measures and all material input capacities and for gaining the maximal economic benefit. Presently, the …     

幂函数对建筑物沉降的回归分析

通过实例推导幂函数对建筑物沉降进行回归分析，并且得出较为精确的结果，同时也说明在选择回归函数的时候，还会受到很多条件影响。     

图像控制点数据库的设计与实现

地面控制点数据是航天航空图像摄影测量几何处理的必需数据。文中首先比较了控制点数据的存储管理方式，即采用文件系统方式与数据库方式的优缺点；接着分析了控制点图像数据的特征，从而提出了图像控制点数据的数据库存储方案，讨论了图像控制点数据库的查询方法；最后结合文中的方法，设计并且实现了一个控制点图像数据库管理与应用实验系统。通过分析认为，建立控制点图像数据库是重复利用控制点资源的有效途径。     

基于EM算法和单幅雷达图像阴影的控制点坡度校正

对在我国现有的条件下进行控制点坡度校正的必要性进行了阐述，并分析了EM算法。根据EM算法以及基于区域增长的余弦散射模型建立了控制点坡度校正模型，并用河北省张北地区的雷达影像进行了实验，取得了较高的精度初值。