双平方根波动方程偏移速度分析   总被引：3，自引：2，他引：1       下载免费PDF全文

刘奇琳  刘伊克  常旭 《地球物理学报》2009,52(7):1891-1898

传统的剩余校正（RMO）偏移速度分析方法基于走时原理,在陡倾角和欠照明地区,因为不能得到充分的角度域信息而失效.本文将展示一种基于波场延拓理论的偏移速度分析方法,即波动方程偏移速度分析（WEMVA）.这种方法先利用成像优化方法获得剩余成像,再利用剩余成像反演剩余速度.此类方法继承了波动方程偏移方法的优点和缺点.波动方程偏移速度分析是一种线性反演方法,它要求对Born近似的展开序列作一阶截断.高阶部分的丢失必然带来巨大的截断误差,因此剩余成像必须也进行线性化,以适应大速度扰动和大延拓步长.因此,在此类算法中,剩余成像的获取和线性化是偏移速度分析的关键.在叠前偏移算子中,因为双平方根算子的数学表达式更为简洁,所以本文基于对波动方程偏移速度分析初步讨论,并通过模型验证其原理.  相似文献   

Wave train model for knickpoint migration     

Nicolas Loget  Jean Van Den Driessche 《Geomorphology》2009,106(3-4):376-382

Rivers respond to a drop in their base level by incising the topography. The upstream propagation of an incision, as usually depicted by a knickpoint migration, is thought to depend on several parameters such as the drainage area, lithology, and the amplitude of the base level drop. We first investigate the case of the Messinian Salinity Crisis that was characterized by the extreme base level fall (1500 m) of the Mediterranean Sea at the end of the Miocene. The response of drainage areas of three orders of magnitude (10³ to 10⁶ km²) highlights the dominant role of the drainage area (with a square root relationship) in controlling the knickpoint migration after a base level fall. A compilation of mean rates of knickpoint propagation for time durations ranging from 10² to 10⁷ years displays a similar relationship indicating that successive wave trains of knickpoint can migrate in a river: first, wave trains linked to the release of the alluvial cover and then, wave trains related to the bedrock incision, which correspond to the real time response of rivers. Wave trains with very low retreat rates (long lived knickpoints > 1 My) rather correspond to the response time of regional landscape.  相似文献   

广义地震活动窗及其对震前异常过程的跟踪应用   总被引：1，自引：1，他引：0  

王琤琤  刘红桂  王炜  陈兴东  梅卫萍  张晓勇 《地震》2000,20(4):19-27

提出了广州地震窗的概念,并以此作为研究范围以突出局部构造特点。用多年地震频次等值线划分广义地震窗的方法,在中国东部得到４５个广义地震窗,它们具有明显的构造意义,应用原有地震活动参数提出一个相对指标ｆ,用以消除局部的地域特点和地震活动涨落的时段特点,提高原指标的异常信息提取能力。用地震活动指数Ａ（ｂ）值的相对指标ｆ（Ａ（ｂ）,提出了用多窗异常组合图综合平面的时间的三维信息以跟踪异常过程,结果显示主震  相似文献   

难降解有机污染物在土壤中的迁移转化   总被引：8，自引：0，他引：8  

高凡  贾建业  杨木壮 《热带地理》2004,24(4):337-340,345

从吸附、渗漏、光降解和生物降解等迁移转化途径入手,总结了多氯联苯(PCBs)、多环芳烃(PAHs)和多氯代二恶英(PCDDs/PCDFs)等难降解有机污染物在土壤中迁移、转化的研究进展,结合土壤污染发展的特点,把大气-水-土壤-生物作为一个有机整体来研究难降解有机污染物在不同环境界面上的迁移、转化规律是今后土壤中难降解有机污染物迁移转化的研究方向,加强污染物之间相互作用机理的研究和提高土壤中难降解有机污染物的降解速率与深度是需要进一步解决的关键问题.  相似文献   

The labour-market impact of migration to rural areas     

Allan M. Findlay  David Short  Aileen Stockdale 《Applied geography (Sevenoaks, England)》2000,20(4):257

An economic audit of the labour-market impact of in-migration to rural Scotland provides evidence that migrants make rather than take jobs. A survey of 689 households in six study areas selected from across rural Scotland provides the basis for examining the scale and nature of job growth associated with in-migration. Job multipliers are calculated by migrant type and by economic sector.  相似文献   

中国隧道及井巷地震波法超前探测技术研究分析   总被引：8，自引：0，他引：8  

张平松  吴健生 《地球科学进展》2006,21(10):1033-1038

自20世纪90年代以来,反射地震波法作为一种主要的超前探测技术在我国国内隧道及井巷工程中取得了诸多成功应用的探测实例,同时在应用中不同探测方法也存在不少问题。文章结合国内外超前探测中应用较为广泛的TSP法、负视速度法、HSP法、TRT法、ISIS系统等反射波探测技术加以阐明,分析了国内超前探测技术应用与研究的现状,指出隧道及井巷超前探测数据采集与处理过程中存在的不足,并进一步提出超前探测研究在正反演理论、数据采集、偏移成像技术等方面应该注意的问题,超前探测的目标是要建立和完善一套实时的巷道前方地质体的动态监测与预报系统。  相似文献   

The effects of air transportation on the movement of labor   总被引：1，自引：0，他引：1  

Kenneth John Button  Henry Vega 《GeoJournal》2008,71(1):67-81

The effects of the deregulation of airlines markets and the new technologies that have been introduced into air transportation have been heavily studied. Much of this analysis has been on the impacts on the industry and the immediate welfare implications for passengers and, to a lesser extent, cargo consignors. This study looks at the longer-term effects of the modern air transportation system on labor markets and labor migration. The growth of the service sector, the emergence of more flexible manufacturing techniques, the reduction in trade-barriers, and the creation of more sophisticated financial markets have led to greater mobility in production and in capital movement. This has been explored to some extent. Labor is, however, also more mobile - for example, since the admission of Poland to the European Union some 465,000 Polish workers have joined the UK labor market. Air transportation facilitates easier migration, makes short-term, long-distance migration viable, and allows migrants to maintain contact with their home country. Within larger countries, such as the US, there has also been a growth in long distance “week-day” migration as spouses work in different parts of the country to be reunited at weekends. The study makes use of aggregate data to look at trends in international labor movements particularly concerning the European situation, and, to a lesser extent, at recent developments within the US. It is concerned both with what is going on in terms of the use being made of air transportation by migrants and the light that this may shed on migration theory.

Kenneth John ButtonEmail:

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1970年以来华东地区地震活动主体区的迁移   总被引：3，自引：0，他引：3       下载免费PDF全文

顾方琦  张春芝  张枝榴  陈礼 《地震地质》2001,23(3):475-480

在已有工作基础上，对华东地区1970年以来的地震活动特征从时序演化和空间分布两方面作了分析，发现该地区地震在时序上存在前后两个演化过程相似的活动时段，并在空间分布上有着较好的分区性，地震活动主体区域存在明显的迁移。该研究结果有助于华不地区今后地震趋势分析。  相似文献   

横向各向同性介质中地震波速度分析及其意义   总被引：2，自引：4，他引：2  

张秉铭  滕吉文 《地球物理学进展》1997,12(1):53-60

在地震学有关领域中，地下介质的薄互层特性与裂隙的定向人布在长波长假设下会产生等效的地震各向异性特性，地震波速度随传播方向和深度发生的变化引起了广大地球物理工作者的广泛兴趣，因为速度拾取的正确与否，会直接影响到油气勘探中动校、偏移、ＡＶＯ和时深转换的结果。本文着重讨论了传统速度分析的局限性，分析了薄互层引起的横向各向同性介质中速度分析的现状和结果，实例讨论了各向异性效应对偏移处理的影响，表明各向异性  相似文献   

新疆强震活动的迁移特征     

白超英  李茂玮 《内陆地震》1991,5(2):113-118

结合新疆构造活动的特点及地震活动的分区,探讨了境内强震活动的迁移特征,结果表明新疆强震活动始于乌恰地区,分别沿南天山西段由南向北迁移和沿西昆仑带由西向东迁移。其迁移方式主要表现为天山带强震活动由低纬向高纬地区成组迁移,各带内次级活动区的往返迁移。研究结果将为判断新疆各区(带)地震活动的趋势及强震危险地区提供依据。  相似文献