附有条件的参数平差模型的有偏估计   总被引：1，自引：0，他引：1  

归庆明  张建军 《测绘工程》2000,9(1):26-30

讨论附有条件的参数平差模型参数的有偏估计问题。提出了约束岭估计和约束主成分估计,并证明了它们的优良性质,最后给出了一个算例,验证了所得结果。  相似文献   

The role of constraints on joint hypocentre determination in seismotectonic studies     

Rodolfo Console  Rita Di Giovambattista  Aldo Di Sanza  Paolo Favali   Giuseppe Smriglio 《Geophysical Journal International》2000,143(1):129-141

In this paper we show how the performance of the joint hypocentre determination (JHD) method can be improved, leading to reduced instability in cases close to singularity. The method has been extended by imposing a number of constraints introduced by other authors, and adding a new one. We tested the stability of the method and the relative advantages of the various constraints by simulating a geometrical space distribution of hypocentres recorded by a regional seismic network. We then applied this method to deep earthquakes that occurred in the Southern Tyrrhenian Sea subduction zone and to the seismicity of the Northern Apennines, which is moderately deeper than the typical shallow seismicity of the Apennines. The results obtained from the analysis of synthetic data and actual earthquakes confirm that the JHD method produces less scatter in the hypocentral determinations with respect to the standard locations. The main conclusion of our study is that we can significantly reduce the systematic mislocations that result from applying JHD to very clustered seismicity if we introduce the appropriate set of constraints.  相似文献   

基于不等式约束的三维电阻率探测混合反演方法   总被引：2，自引：2，他引：0       下载免费PDF全文

刘斌  刘征宇  宋杰  聂利超  王传武  陈磊 《地球物理学报》2017,60(2):820-832

三维电阻率探测的线性反演和非线性反演中均存在着多解性的固有难题.电阻率线性反演方法的效率较高,但反演结果对初始模型的依赖性较强,易陷入局部极小;而非线性反演方法不依赖初始模型,但搜索效率极低,尚未见到关于三维电阻率非线性反演的文献.针对上述问题,融合线性与非线性反演方法的互补优势,提出了最小二乘法(线性方法)与改进遗传算法(非线性方法)相结合的混合反演方法的概念和思想.首先,提出了将介质电阻率变化范围作为不等式约束引入反演方程的思路,以实现压制多解性、提高可靠性的目标.提出了宽松不等式约束和基于钻孔推断的局部严格不等式约束的获取及定义方法.在此基础上,分别提出了基于不等式约束的最小二乘线性反演方法和遗传算法非线性反演方法.其次,对于遗传算法在变异搜索方向控制、初始群体产生等方面进行了改进,优化了其搜索方向和初始群体多样性.然后,提出了混合反演方法及其实现方案,利用改进遗传算法进行第一阶段反演,发挥其对初始模型的依赖程度低的优势,搜索到最优解附近的空间,输出当前最优个体;利用最小二乘法进行第二阶段反演,将遗传算法得到的当前最优个体作为初始模型,在最优解附近空间执行高效率的局部线性搜索,最终实现地电结构的三维成像.最后,开展了合成数据与实际工程算例验证,与传统最小二乘方法进行了对比,发现混合反演方法在压制多解性、摆脱初始模型依赖和提高反演效果方面有较好效果.  相似文献   

基于GRACE的空间约束方法监测华北平原地下水储量变化   总被引：3，自引：0，他引：3       下载免费PDF全文

冯伟  王长青  穆大鹏  钟敏  钟玉龙  许厚泽 《地球物理学报》2017,60(5):1630-1642

华北平原作为我国重要的工农业基地和政治经济中心,面临着严重的水资源危机.因此,开展对华北平原地下水储量变化的监测工作具有重要现实意义与科学价值.本文基于GRACE重力卫星的空间约束方法,研究了华北平原地下水储量变化的时空分布规律,并与地面水井实测与地下水模型结果进行了综合比较和分析.结果表明:2002-2014年,华北平原地下水存在明显的长期亏损,GRACE估计的亏损速率为-7.4±0.9 km~3·a~(-1),而地面水井资料估计的浅层地下水亏损速率为-1.2 km~3·a~1,对比两者之间的差异可以发现,华北平原的地下水亏损以深层地下水为主.2002-2008年,GRACE估计的华北平原地下水亏损速率为-5.3±2.2 km~3·a~(-1),这与华北平原两个地下水模型得到的平均亏损速率-5.4 km~3·a~(-1)十分吻合.通过华北平原区域地下水模型的独立验证,说明GRACE可以有效评估华北平原的地下水储量变化趋势.除了长期亏损的趋势项之外,华北平原地下水还存在明显的年际变化特征,并与该地区年降雨量变化特征一致.在降雨偏少的2002年、2005-2009年和2014年,华北平原地下水储量显著减少.在空间分布上,GRACE结果表明,华北平原的地下水储量减少主要发生在山前平原和中部平原区,这也与水井实测资料和区域地下水模型结果较为吻合.与GRACE和区域地下水模型相比,目前的全球水文模型仍无法准确估计华北平原地下水变化的空间分布和亏损速率.上述研究表明,GRACE提供了评估华北平原地下水储量变化的重要监测手段.  相似文献   

Late Holocene slip rate and average recurrence interval of great earthquakes on the Shangzhi segment of the Yilan‐Yitong Fault Zone,northeastern China: Constraints from paleo‐earthquakes and historical written records          下载免费PDF全文

Zhongyuan Yu  Peizhen Zhang  Wei Min  Qinghai Wei  Yugang Liu 《Island Arc》2018,27(1)

The Yilan‐Yitong Fault Zone (YYFZ) is considered to be the key branch of the Tancheng‐Lujiang Fault Zone (TLFZ) in northeastern China. Although the Mesozoic and early Cenozoic deformation of the YYFZ has been studied intensively over the past century, few estimates of slip rate and recurrence interval of large earthquakes in the late Quaternary, which are the two most important parameters for understanding the potential seismic hazard of this crucial structure, were obtained. Based on integrated interpretations of high resolution satellite images and detailed geologic and geomorphic mapping, linear landforms were identified, including fault scarps and troughs, along the Shangzhi segment of the YYFZ, which exceeds 25 km in length. Synthesized results of trench excavations and differential GPS measurements of terrace surfaces indicate that two events (E1, E2) occurred along the Shangzhi segment during the late Holocene, which resulted in 3.2 ±0.1 m of total vertical co‐seismic displacement with clear features of thrust motion. ¹⁴C dating of samples suggests that event E1 occurred between 440 ±30 years BP and 180 ±30 years BP and that event E2 occurred between 4 090 ±30 years BP and 3 880 ±30 years BP, which indicates that the minimum vertical slip rate of the Shangzhi segment of the YYFZ has been approximately 0.8 ±0.03 mm/year during the late Holocene. Constraints from paleo events and the slip rate suggest that the average recurrence interval of major earthquakes on the YYFZ is 3 800 ±200 years. Historical documents in Korea show that event E1 possibly corresponds to the earthquake that occurred in AD 1810 (the Qing Dynasty in Chinese history) in the Ningguta area, which had surface‐wave magnitude (Ms) of 6.8–7.5. Studies of kinematics show that the right‐lateral strike‐slip with a reverse component has been dominant along the YYFZ during the late Holocene.  相似文献   

Incorporating known petrophysical model in the seismic full-waveform inversion using the Gramian constraint     

M. Malovichko  N. Khokhlov  N. Yavich  M. S. Zhdanov 《Geophysical Prospecting》2020,68(4):1361-1378

In this paper, we develop a general approach to integrating petrophysical models in three-dimensional seismic full-waveform inversion based on the Gramian constraints. In the framework of this approach, we present an example of the frequency-domain P-wave velocity inversion guided by an electrical conductivity model. In order to introduce a coupling between the two models, we minimize the corresponding Gramian functional, which is included in the Tikhonov parametric functional. We demonstrate that in the case of a single-physics inversion guided by a model of different physical type, the general expressions of the Gramian functional and its gradients become simple and easy to program. We also prove that the Gramian functional has a non-negative quadratic form, so it can be easily incorporated in a standard gradient-based minimization scheme. The developed new approach of seismic inversion guided by the known petrophysical model has been validated by three-dimensional inversion of synthetic seismic data generated for a realistic three-dimensional model of the subsurface.  相似文献   

强造斜致绳索取心钻具折断分析     

卢秋平 《地质与勘探》2020,56(2):445-450

在定向钻探固体矿产领域,通常在造斜段使用螺杆钻具,大部分的工作量采用取心回转钻进。造斜段使用螺杆钻具,钻杆不回转,受力较简单;如遇强造斜转换绳索取心钻具稳斜钻进,下部钻具组合容易出现回转困难、下不到底的技术难题,甚至出现丝扣折断事故。为避免强造斜对绳索取心钻具的影响,本文通过建立强造斜段对绳索取心钻具的几何约束变形模型,量化分析强造斜段岩心外管长度与造斜强度、环空间隙之间的约束关系,提供了可快速预判下部钻具参数能否满足强造斜安全钻进的方法。该方法在山东某铁矿定向孔的强造斜致下部钻具折断的事故处理中,通过对绳索取心钻具安全计算模型校核和调整钻具参数,实现了绳索取心钻具通过造斜率0.62°/m的强造斜段安全钻进至靶点,证明对强造斜绳索取心工具安全钻进预测和事故处理计算具有指导意义。  相似文献   

On Fröhlich's solution for Boussinesq's problem     

A. P. S. Selvadurai 《国际地质力学数值与分析法杂志》2014,38(9):925-934

The concentration factor introduced by O. K. Fröhlich is visualized as a procedure for examining the pattern of load transfer from surface loads to the interior of a geomaterial. The historical details that led to the introduction of the concentration factor are scant although it is widely used in the area of soil mechanics problems associated with tillage‐induced soil compaction. The purpose of this note is to examine the concentration factor in terms of the geomechanics of an elastic continuum and to identify the precise conditions that are satisfied by the distribution of stresses and strains that accommodate the concentration factor. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Regional Differentiation and Classification for Carrying Constraints on the Resources and Environment of China     

ZHANG Xuefei  XU Yong  LI Lijuan  DAI Erfu  XU Weihua 《资源与生态学报(英文版)》2018,9(2):135-145

Research on the relationship between national resource constraint-region types and environmental carrying capacity is essential for the continued development of Chinese industrialization and urbanization. Thus, utilizing a series of key indexes including the per-capita potential of available land resources, the per-capita potential of available water resources, the degree of environmental stress, and the degree of ecological restriction, a step-by-step, integrated measuring method is presented here to understand the constrained carrying elements of water and land resources as well as environment and ecology. Spatial differences are analyzed and area types classified at the county level across China. Results reveal that: (1) Almost 90% of China is strongly constrained by both resources and the environment, while nearly 50% of national territory is strongly constrained by two elements, especially in areas of intensive population and industry to the east of the Helan-Longmen Mountain line; (2) Densely populated areas of eastern and central China, as well as on the Tibetan Plateau, are strongly constrained by a shortage of land resources, while North China, the northwest, northeast, the Sichuan basin, and some southern cities are experiencing strong constraints because of water shortages. In contrast, the North China plain, the Yangtze River delta, northern Jiangsu, Sichuan province, Chongqing municipality, Guizhou and Guangxi provinces, the northeast plain, and the northern Loess Plateau are constrained by high levels of environmental stress. Areas of China that are strongly ecologically constrained tend to be concentrated to the southwest of the Tianshan-Dabie Mountain line, as well as in the northeast on the Loess Plateau, in the Alashan of Inner Mongolia, in northeast China, and in the northern Jiangsu coastal area; (3) Constraints on national resources and environmental carrying capacity are diverse and cross-cut China, meanwhile, multi-element spatial distribution does reveal a degree of relative centralization. With the exception of the Tibetan Plateau which is resources-ecological constraint , other areas subject to cross constraints are mainly concentrated to the east of the Helan-Longmen Mountain line.  相似文献   

The Internet, mobile phone and space-time constraints   总被引：2，自引：0，他引：2  

Tim Schwanen  Mei-Po Kwan   《Geoforum》2008,39(3):1362-1377

While the implications of information and communication technologies (ICTs) for daily travel and activities have been studied extensively, there is only scant attention paid to the relations between ICTs and space-time constraints. This study therefore explores the extent to which the Internet and mobile phone increase the spatial and temporal flexibility of everyday activities through a review of the literature and empirical research with data from Columbus (Ohio, USA) and Utrecht (The Netherlands). The analysis suggests that the implications of the Internet and mobile phone are complex and dependent on the type of activity, persons involved, technologies and socio-physical context in which they are embedded. Various regularities can, however, be detected. For the study participants, the Internet and mobile phone relax temporal constraints to a stronger degree than they enhance spatial flexibility. There are also space-time constraints that seem to persist or have come about because of ICT adoption. Finally, it appears that the Internet and mobile phone at best consolidate differences between men and women in the space-time constraints associated with everyday activities.  相似文献