Efficient global matrix approach to the computation of synthetic seismograms   总被引：3，自引：0，他引：3  

Henrik Schmidt  Gerard Tango 《Geophysical Journal International》1986,84(2):331-359

Summary. A numerically efficient global matrix approach to the solution of the wave equation in horizontally stratified environments is presented. The field in each layer is expressed as a superposition of the field produced by the sources within the layer and an unknown field satisfying the homogeneous wave equations, both expressed as integral representations in the horizontal wavenumber. The boundary conditions to be satisfied at each interface then yield a linear system of equations in the unknown wavefield amplitudes, to be satisfied at each horizontal wavenumber. As an alternative to the traditional propagator matrix approaches, the solution technique presented here yields both improved efficiency and versatility. Its global nature makes it well suited to problems involving many receivers in range as well as depth and to calculations of both stresses and particle velocities. The global solution technique is developed in close analogy to the finite element method, thereby reducing the number of arithmetic operations to a minimum and making the resulting computer code very efficient in terms of computation time. These features are illustrated by a number of numerical examples from both crustal and exploration seismology.  相似文献   

Numerical Study on Vortices in the Middle Layer of Flow around a Large Mountain under Rotating Stratified Conditions     

Yu?HozumiEmail author  Hiromasa?Ueda 《Pure and Applied Geophysics》2005,162(10):1779-1793

Generation of cyclonic vortices in the middle layer of flow around a large mountain like Tibet and Rocky was investigated by means of a 3-D nonhydrostatic meteorological prognostic model. Special attention was paid to the effects of the earth’s rotation and stratification on the vortices detached successively from the slope of a high and large horizontal scale mountain. It was found the successive formation and detachment of such ‘von Karman-like vortices’ occurred in the flow regime at high Rossby numbers Ro and low Froude numbers Fr. It was successfully divided by the criterion of baroclinic instability. This means that if the condition is unstable baroclinically, a lee vortex is destabilized into a three-dimensional one, while under baroclinically stable conditions the lee vortex with vertical axis retains its standing structure and remains long lasting in the middle layer.  相似文献   

热带气旋发生、发展的不稳定理论     

刘式适 《热带海洋学报》1991,(2)

本文在正压无辐散的条件下,讨论了东、西风不连续面上的正压不稳定性。研究指出:这种界面上的扰动总是不稳定的,从而说明了热带气旋常在赤道辐合带(ITCZ)上形成的原因。本文又在考虑了热带气旋内部的层结和基本气流的条件下,讨论了热带气旋发展的热力学和动力学条件。研究指出:层结稳定度和惯性稳定度同时影响热带气旋的发展.当两者都稳定时,热带气旋不发展;当两者之一不稳定时,热带气旋有可能发展;当n~2I~2 (μ~2/a)~2N~2<0时,热带气旋一定发展。  相似文献   

由正入射遥测海底介质参数方法初探     

王恕铨 《中国海洋大学学报(自然科学版)》1994,(4)

通过数值模拟计算发现，对于分层有吸收海底，在层厚已知的条件下，除最下面的介质以外．有可能利用垂直入射的脉冲声波遥测各层的密度、声速与吸收系数。此法的要点是，根据入射波和层参数的假设值算得反射信号，与实际反射信号比较；然后改变参数再作计算，直到误差最小为止．此时对应的层参数即为介质参数值实际的估计值。指出根据这种方法有可能实现以自适应方法遥测分层海底的介质参数。  相似文献   

求解各向异性分层介质中水平电偶极辐射的实用方法     

钮金真  陈志雨 《中国海洋大学学报(自然科学版)》2002,32(5):822-826

用矩阵对角化方法求解了在各向异性分层介质中水平电偶极的辐射问题 ,并引入“过渡矢量”,利用其传播特性求得定解 ,此方法简单实用 ,不要求相似变换矩阵归一化。作为应用 ,具体计算了电离层被加热产生的极低频源在几千公里范围水下不同深度远处接收场强的量级  相似文献   

高相干点地基InSAR的大气延迟纠正     

张夕宁  杨红磊  姜君  彭军还  徐佳佳 《测绘科学》2017,42(1)

针对目前地基合成孔径雷达干涉测量技术中大气影响造成的相位延迟校正方法存在的校正精度低、方法复杂、技术要求高等不足,提出了一种基于高相干点的地基InSAR大气延迟相位函数模型校正方案。该方案不需多幅SAR影像,不需人工布点,节省了大量人力物力。以高相干点的相干值作为权阵参与计算,该方法可得到更精确的校正结果。运用该方法将地基雷达对山西省吕梁市林家坪工程滑坡获取的数据进行大气延迟改正的实验。结果表明:所提方案不仅处理方法简单,改正效果明显,而且能满足绝大多数类似工程的精度要求,更为经济实用。  相似文献   

高度城市化地区土地利用变化分析及效益评价——以深圳市为例     

王珍香  黄继先 《测绘与空间地理信息》2017,40(9)

为研究全国第二次土地调查以后高度城市化地区的土地利用变化及效益,本文以深圳市为例,利用其2009—2014年土地变更调查数据,从土地利用结构、土地利用程度、土地利用空间格局以及动态度等多个方面进行分析,并通过熵值法从社会、经济、生态和环境4个角度选取23个指标评估深圳市的土地利用效益及各效益的调度发展状况。研究结果表明:1)深圳市土地利用率已达93%,建设用地率达48.49%,土地综合利用程度逐年提高,土地利用空间格局趋向单一,各指数年变化率均逐渐降低;2)社会效益、经济效益和环境效益提高,生态效益降低,综合效益逐年提高;3)各分项效益子系统从基本协调上升到高度协调。深圳市的土地利用变化分析及效益评价,为深圳市的土地利用总体规划及可持续土地利用提供了一定的参考依据,并对其他高度城市化地区的土地利用具有借鉴价值。  相似文献   

基于楼盘表和户型图的分层分户模型建设     

刘怡菲  郭月肖  杨耀环 《测绘与空间地理信息》2017,40(Z1)

随着智慧城市建设的不断升级,城市管理向精细化和智能化方向快速发展.分层分户模型可以承载更复杂、更立体、更详细、更精确的信息,以供全面综合管理、大数据分析和应急指挥使用.本文以"数字郑州三维地理信息及应用服务系统"项目建设实际情况为背景,探索和实现了在SuperMap GIS平台环境下,基于楼盘表提供的层户信息与户型图提供的分户信息,通过数字线划图进行建筑底面定位,利用地名地址将楼盘表和户型图与数字线划图进行关联挂接,并根据LiDAR点云数据的高度信息,快速自动化地建设郑州市800 km2内所有建筑物的分层分户模型的技术方法.进一步探索了通过模型成果与房管信息和公安户籍信息挂接,建立"以图管房、以房管人"的新管理模式,有效提升了政府管理和决策水平.本文提出的方法技术路线先进,实操性强,具有重要的应用推广价值.  相似文献   

Precarity among highly educated migrants: college graduates in Beijing,China     

Hao Wang  Wei Li 《Urban geography》2017,38(10):1497-1516

The growing knowledge-based and service economies in megacities like Beijing and Shanghai have attracted large numbers of highly educated migrants, whereas their living conditions have drawn plenty of attention. In examining these issues, we conducted an empirical study regarding the precarity among highly educated migrants in Beijing. There are some structural and institutional factors underneath the highly educated migrants’ precarity, as the household registration (hukou) system still plays a significant role in accessing social welfare (urban public housing) and job opportunities in Beijing. Although the new urban poverty has occurred in the city as a result of the questionable policies regarding social distribution and welfare, it can also be argued that some of these migrants view temporary precarity as a strategy toward future upward social mobility – the hope of doing better over the long term.  相似文献   

地理探测器：原理与展望   总被引：261，自引：30，他引：231  

王劲峰  徐成东 《地理学报》2017,72(1):116-134

空间分异是自然和社会经济过程的空间表现,也是自亚里士多德以来人类认识自然的重要途径。地理探测器是探测空间分异性,以及揭示其背后驱动因子的一种新的统计学方法,此方法无线性假设,具有优雅的形式和明确的物理含义。基本思想是：假设研究区分为若干子区域,如果子区域的方差之和小于区域总方差,则存在空间分异性;如果两变量的空间分布趋于一致,则两者存在统计关联性。地理探测器q统计量,可用以度量空间分异性、探测解释因子、分析变量之间交互关系,已经在自然和社会科学多领域应用。本文阐述地理探测器的原理,并对其特点及应用进行了归纳总结,以利于读者方便灵活地使用地理探测器来认识、挖掘和利用空间分异性。  相似文献