Deformation and stress regimes in the Hellenic subduction zone from focal Mechanisms

Fault plane solutions for earthquakes in the central Hellenic arc are analysed to determine the deformation and stress regimes in the Hellenic subduction zone in the vicinity of Crete. Fault mechanisms for earthquakes recorded by various networks or contained in global catalogues are collected. In addition, 34 fault plane solutions are determined for events recorded by our own local temporary network on central Crete in 2000–2001. The entire data set of 264 source mechanisms is examined for types of faulting and spatial clustering of mechanisms. Eight regions with significantly varying characteristic types of faulting are identified of which the upper (Aegean) plate includes four. Three regions contain interplate seismicity along the Hellenic arc from west to east and all events below are identified to occur within the subducting African lithosphere. We perform stress tensor inversion to each of the subsets in order to determine the stress field. Results indicate a uniform N-NNE direction of relative plate motion between the Ionian Sea and Rhodes resulting in orthogonal convergence in the western forearc and oblique (40–50^∘) subduction in the eastern forearc. There, the plate boundary migrates towards the SE resulting in left-lateral strike-slip faulting that extends to onshore Eastern Crete. N110^∘E trending normal faulting in the Aegean plate at this part is in accordance with this model. Along-arc extension is observed on Western Crete. Fault plane solutions for earthquakes within the dipping African lithosphere indicate that slab pull is the dominant force within the subduction process and responsible for the roll-back of the Hellenic subduction zone.     

拉格朗日和切比雪夫多项式在精密星历插值中的应用

文中分别采用拉格朗日多项式和切比雪夫多项式,对时间间隔为15 min的IGS精密星历进行内插和拟合,将插值结果与原始精密星历进行比较。在此基础上分析了不同阶数下的插值精度,并将这两种方法做一些比较,得出结论:采用一定阶次的拉格朗日和切比雪夫多项式做精密星历内插均达到毫米级的精度,且两种方法的插值效果比较接近。     

广义延拓法在IGS精密星历插值中的应用

利用广义延拓插值法对IGS精密星历进行插值,探讨了广义延拓插值数学模型中单元域节点、延拓域节点、逼近函数项数三个参数与插值精度之间的关系,并与传统经典的Lagrange多项式插值法进行比较分析。实际算例表明,只要选取适当的参数,广义延拓插值法拥有比Lagrange多项式插值法更高的精度。     

北斗海上无源定位解析求解新方法

提出一种北斗无源定位解析求解新方法。该方法具有很高的计算效率,并在一定程度上减弱了几何观测图形欠佳对定位精度的影响。仿真计算结果表明,新方法比“三星+高程”法和双曲线解析求解法具有更高的计算效率和定位精度。     

基于Arc/Info的线状要素制图综合算法

制图综合是当前地图学家们关注的焦点问题和前沿问题,在地图中线状要素所占比重往往最高,因此它是制图综合的一个重要方面。本文分析了线状要素制图综合的特点及Arc/Info软件的综合功能,并在此基础上提出了基于Arc/Info解决线综合问题的策略;然后以土地利用专题图作为实验数据,给出其在Arc/Info中的实现算法,同时对不同的实现方法进行比较,最后分析实验结果。     

附不等式约束平差的理论与方法研究

附不等式约束平差能充分利用已有的各种知识和信息,因而越来越得到关注,它在GPS数据处理、变形监测及方差估计等领域中都得到广泛的应用。目前,国内外对附不等式约束平差问题进行大量研究,文中主要综述附不等式约束平差问题的最新研究成果,系统介绍附不等式约束平差的理论,同时探讨附不等式约束平差的发展方向。     

CDMA VPDN构建IP数字测震台网

通过对目前CDMA2000 1x网络技术和构架的深入介绍,可了解CDMA VPDN的应用原理。针对CDMA传输的早期台网方案在应用中的不足,以四川省数字测震台网为例,详细介绍了利用CDMA VPDN构建IP数字测震台网的组网方式和网络构架。最后,对该方案使用中存在的一些常见问题给予了详细分析并针对问题提出了处理方法和建议。     

A semi-analytical solution for the three-dimensional advection–diffusion equation considering non-local turbulence closure

Atmospheric air pollution turbulent fluxes can be assumed to be proportional to the mean concentration gradient. This assumption, along with the equation of continuity, leads to the advection–diffusion equation. Moreover, large eddies are able to mix scalar quantities in a manner that is counter to the local gradient. In this work we present a semi-analytical solution for the three-dimensional steady-state advection–diffusion equation, considering non-local turbulence closure using the Generalized Integral Advection Diffusion Multilayer Technique (GIADMT). We report some examples of applications of the new solution for two different datasets and for a water tank experiment.     

Mantle flow beneath the Asian continent and its force to the crust

Introduction In order to understand the formation of the geological structure and its evolution of the Asian continent, it is needed to investigate the driving forces from the around continents and oceans and from its underlying mantle as well. The super parallel computer has been used to simulate the geodynamical processes in the lithosphere and mantle for a long time in many international works (Bird, 1995; Tackley, 1995). We also calculated the patterns of the global mantle convection on o…