北京地区大气污染分布的“南北两重天”现象   总被引：11，自引：2，他引：9  

董芬  王喜全  王自发  晏平仲 《气候与环境研究》2013,18(1):63-70

利用2006年北京地区空气质量监测站和自动气象站网资料,以及华北地区中尺度气象观测资料,分析了北京地区大气污染分布的“南北两重天”现象.通过对此类现象发生过程中天气形势和北京地区气象要素的分析,指出了造成该现象的天气学成因和气象要素特征.研究结果表明,2006年北京共发生47次“南北两重天”现象,其中大部分发生在秋、冬季的午夜至次日上午,且多为南差北好的污染物分布情景.该现象的发生与北京地区中-α尺度天气系统活动的一些特征有关,特别是与干冷空气进入北京地区的路径以及移动速度的区域差异有关.另外,在弱天气系统控制下,北京西南部地区经常出现的小尺度辐合型流场,也是形成北京地区“南北两重天”现象的重要原因.  相似文献   

Robustness of the holistic seismic risk evaluation in urban centers using the USRi   总被引：2，自引：2，他引：0  

Mabel-Cristina Marulanda  Omar D. Cardona  Alex H. Barbat 《Natural Hazards》2009,49(3):501-516

The Urban Seismic Risk index (USRi) published in a previous article (Carreño et al., Nat Hazards 40:137–172, 2007) is a composite indicator that measures risk from an integrated perspective and guides decision-making for identifying the main interdisciplinary factors of vulnerability to be reduced or intervened. The first step of the method is the evaluation of the potential physical damage (hard approach) as a result of the convolution of the seismic hazard with the physical vulnerability of buildings and infrastructure. Subsequently, a set of social context conditions that aggravate the physical effects is also considered (soft approach). According to this procedure, the physical risk index is evaluated for each unit of analysis from existing loss scenarios, whereas the total risk index is obtained by multiplying the former index by an impact factor using an aggravating coefficient, based on variables associated with the socio-economic conditions of each unit of analysis. The USRi has been developed using the underlying holistic and multi-hazard approach of the Urban Risk Index framework proposed for the evaluation of disaster risk in different megacities worldwide. This article presents the sensitivity analysis of the index to different parameters such as input data, weights and transformation functions used for the scaling or normalization of variables. This analysis has been performed using the Monte Carlo simulation to validate the robustness of this composite indicator, understanding as robustness how the cities maintain the ranking as well as predefined risk level ranges, when compared with the deterministic results of risk. Results are shown for different cities of the world.  相似文献   

On-chip earthquake simulation model using potentials     

I. G. Georgoudas  G. Ch. Sirakoulis  E. M. Scordilis  I. Th. Andreadis 《Natural Hazards》2009,50(3):519-537

A two-dimensional (2-D) Cellular Automata (CA) dynamic system constituted of cells-charges has been proposed for the simulation of the earthquake process. The CA model has been calibrated with the use of real data. The calibration incorporates major seismic characteristics of the area under test. The simulation results are found in good quantitative and qualitative agreement with the recorded Gutenberg–Richter (GR) scaling relations. The model is enriched with a powerful multi-parameter interface that enables the user to load real data from different regions. This paper examines the on-chip realisation of the model and its instrumentation. The CA model hardware implementation is based on Field Programmable Gate Array (FPGA) logic. It utilises an array of 32 × 32 cells. Parameters that construct the local CA rule constitute the input data. The initial seed, which to some extent corresponds to the seismic features of the area under test, is loaded in a semi-parallel way and the process is completed in a certain number of time steps. The automatic response of the processor provides the corresponding GR scaling law of the area under study. The hardware implementation of the CA-based earthquake simulation model is advantageous in terms of low-cost, high-speed, compactness and portability features. It can operate as a preliminary data-acquisition filter that accelerates the evaluation of recorded data as far as its origin time, spatial and magnitude completeness and quality are concerned. Software that performs reliable automatic phase picking, as well as data elaboration, can be assembled next to the earthquake recording instruments (the whole network) output to assure a quick and reliable iteration of the focal parameters of a recorded earthquake (epicentre coordinates, focal depth and magnitude). The dedicated processor can be accommodated right after this stage (before any manual elaboration) focusing on the near real-time development of a reliable qualitative dynamical seismic record and a mapping of the seismic characteristics of the area.  相似文献   

北京白查A型花岗岩的地球化学特征及其成因与构造指示意义   总被引：17，自引：6，他引：11  

汪洋 《岩石学报》2009,25(1):13-24

位于北京昌平区的年龄为127Ma的白查岩体是一个晶洞过碱性花岗岩岩株,其侵位于燕山造山带西段的八达岭岩基中。白查岩体具有高硅、Zr、Ga、Pb、HFSE和REE含量,高Fe/Mg和Ga/Al比值,强烈亏损Ca、Sr、Eu,具有亏损放射性成因Pb同位素的特征。白查岩体属于Dall’Agnol和Oliveira (2007)定义的典型的还原型A型花岗岩,其地球化学特征与燕山带中生代晚期的后石湖山(山海关)和窟窿山A型花岗岩非常相似。白查花岗岩起源于华北克拉通下地壳镁铁质源岩在相对贫水、高温、低氧逸度条件下的低程度部分熔融。综合区域地质背景和该岩体的成岩机制判断,白查花岗岩的形成标志燕山西段造山崩塌阶段的到来。除浙江东南瑶坑过碱性花岗岩外,白查岩体是具有A1型花岗岩元素地球化学特征但并非形成于非造山大地构造背景的过碱性花岗岩的又一个实例。  相似文献   

Vp/Vs Anisotropy and Implications for Crustal Composition Identification and Earthquake Prediction   总被引：1，自引：1，他引：0  

WANG Qian  JI Shaocheng  XU Zhiqin 《《地质学报》英文版》2009,83(4):801-815

Abstract: The ratio of P- to S-wave velocities (Vp/Vs) is regarded as one of the most diagnostic properties of natural rocks. It has been used as a discriminant of composition for the continental crust and provides valuable constraints on its formation and evolution processes. Furthermore, the spatial and temporal changes in Vp/Vs before and after earthquakes are probably the most promising avenue to understanding the source mechanics and possibly predicting earthquakes. Here we calibrate the variations in Vp/Vs in dry, anisotropic crustal rocks and provide a set of basic information for the interpretation of future seismic data from the Wenchuan earthquake Fault zone Scientific Drilling (WFSD) project and other surveys. Vp/Vs is a constant (Ф0) for an isotropic rock. However, most of crustal rocks are anisotropic due to lattice-preferred orientations of anisotropic minerals (e.g., mica, amphibole, plagioclase and pyroxene) and cracks as well as thin compositional layering. The Vp/Vs ratio of an anisotropic rock measured along a selected pair of propagation-vibration directions is an apparent value (Фij) that is significantly different from the value for its isotropic counterpart (Ф0). The usefulness of apparent Vp/Vs ratios as a diagnostic of crustal composition depends largely on rock seismic anisotropy. A 5% of P- and S-wave velocity anisotropy is sufficient to make it impossible to determine the crustal composition using the conventional criteria (Vp/Vs≤1.756 for felsic rocks, 1.7561.944 fluid-filled porous/fractured or partially molten rocks) if the information about the wave propagation-polarization directions with respect to the tectonic framework is unknown. However, the variations in Vp/Vs measured from borehole seismic experiments can be readily interpreted according to the orientations of the ray path and the polarization of the shear waves with respect to the present-day principal stress directions (i.e., the orientation of cracks) and the frozen fabric (i.e., foliation and lineation).  相似文献   

地震海洋学研究进展   总被引：1，自引：0，他引：1  

胡毅  刘怀山  陈坚  许江 《地球科学进展》2009,24(10):1094-1104

传统船舶调查获取海洋水体温盐资料的方法在水平方向上分辨率较低,而用反射地震探测海洋水体特性的方法--地震海洋学,能有效提高海水温盐资料在水平方向上的分辨率.概述了近5年来地震海洋学的发展过程,重点介绍了地震海洋学方法在海洋锋面观测、水团边界划分、海洋内波分析、中尺度涡旋等方面的研究成果,以及AVO、全波形反演等反射地震处理方法在海洋水体特性研究中的应用.比较了地震海洋学方法与声层析技术、高频声技术等声学方法应用于海洋水体特性研究的异同.并展望了下一步研究工作的重点:①有关地震反射剖面的各种参数与海洋水体温盐结构物理模型的联系及其定量分析;②以研究海洋水体特性为目标的地震反射剖面的处理方法;③海洋地震调查历史数据的应用.  相似文献   

地震勘探技术在发现韩岗煤田过程中作用分析          下载免费PDF全文

刘勇  程怡 《江苏地质》2009,33(2):187-190

现代科技发展带来了物探装备和技术新飞跃,探测能力、性能以及准确性有了大幅度提高,使物探方法应用于找矿初期成效非常明显。以发现山东省韩岗煤田为例,说明在找矿方法上要采用物探先行、钻探验证、物探指导钻探的勘查方法,还应在整个井田勘探中均坚持物探在先、钻探验证的勘探原则,减少了钻探盲目性,提高找矿和开发矿产的效率。  相似文献   

北京城市居民的空间感知与意象空间结构   总被引：38，自引：1，他引：37  

冯健 《地理科学》2005,25(2):142-154

对北京城市居民的空间感知进行了问卷调查,从323份感知地图中提取和统计相关数据,并据此分析北京城市居民空间感知的基本类型、构成和发展阶段,以及各种差异性特征。研究表明,北京城市居民的空间感知类型与西方的研究结果大体一致,但存在一定差异;居民居住地域、性别、学历、收入以及出生地的不同,感知地图类型的级别也不相同。感知空间的构成要素在居住地域、年龄、收入和出生地方面差异明显,而发展阶段主要与性别、收入和出生地有关,社会角色和经济收入水平在决定居民感知空间发展阶段方面起到巨大作用。文章最后还根据各种地物和构成要素出现的频率,概括了北京城市意象的空间结构,并发现它与现实中北京城市空间布局的重点极为相似。  相似文献   

基于频率搬移的地震资料约束测井资料外推   总被引：4，自引：0，他引：4       下载免费PDF全文

陆文凯  张善文 《地球物理学报》2004,47(2):354-358

于地震资料本身频带有限的特性,导致在利用地震资料作为约束条件进行测井资料外推时存在奇异性. 文中利用通信中常用的频率搬移技术,将频带有限的地震资料转化成一种频带拓宽的伪超分辨率资料来控制测井资料的外推,从而解决地震资料约束下的测井资料外推技术中的奇异性问题. 并利用同相轴自动追踪和时频分析技术,解决子波时变的问题,实现沿地层自适应地外推测井资料. 对实际资料的测井速度和反射系数外推结果表明, 此法具有较好的应用前景.  相似文献   

基于独立分量分析的多次波自适应相减技术   总被引：29，自引：7，他引：22       下载免费PDF全文

陆文凯  骆毅  赵波  钱忠平 《地球物理学报》2004,47(5):0-891

针对多次波自适应相减这个关键问题,文中首次提出利用独立分量分析技术来实现多次波和一次波的分离（简称ICAAMS）. 现有的多次波自适应相减技术大都是采用输出信号（一次波）能量最小准则,基于二阶统计量的技术. 本文提出的ICAAMS采用了输出信号非高斯性最大准则,并利用高阶统计量来表征非高斯性. 简单的褶积模型和复杂的有限差分模型资料处理结果表明, 本文提出的方法可以有效地分离一次波和多次波.  相似文献