含裂隙介质中的视电阻率各向异性变化   总被引：1，自引：0，他引：1       下载免费PDF全文

解滔  卢军 《地球物理学报》2020,63(4):1675-1694

我国50多年的视电阻率连续观测结果表明,大地震前近震中区域的视电阻率呈现出与主压应力方位有关的各向异性变化,即:垂直于主压应力方向观测的变化幅度最大,平行方向最小或不明显,斜交方向介于二者之间.目前我国定点台站视电阻率观测的探测范围主要在浅层沉积层以内,通常含有较多的含水裂隙.本文将地下岩土介质简化为由固体基质和含流体/气体裂隙组成的固液气三相介质,且基质、流体和气体具有标量形式的电阻率,推导出了包含基质和流体电阻率、裂隙率、饱和度和裂隙面积率因子的电阻率张量表达式.以裂隙的扩展/闭合表示应力作用下裂隙的变化,得到了电阻率随裂隙变化的微分形式,电阻率变化对裂隙体积变化放大系数的表达式和裂隙横向变化对纵向电阻率影响的横向权系数的表达式.在此基础上得到了介质电阻率和视电阻率的各向异性变化特征:对于含水裂隙介质,无论裂隙如何变化,均是最小主轴方向电阻率的变化幅度大于其他方向;对于含水孔隙介质,沿孔隙主要变化方向的主轴电阻率变化幅度大于其他方向.对于各向异性变化,视电阻率和介质电阻率存在π/2的方向差异.相较于含水岩石,无水岩石介质电阻率的各向异性变化不显著.本文提出的电阻率表达式可以对实验室和野外实际观测的许多结果做出合理的解释.  相似文献   

利用海洋重力场变化分析洋底板块运动          下载免费PDF全文

李倩倩  鲍李峰  C. K. Shum 《地球物理学报》2020,63(7):2506-2515

洋底板块运动是地球动力学和全球变化研究的重要内容.本文根据质量迁移与地球外部重力场变化的对应关系,利用不同时期测高资料推算的1995—2019全球海洋重力场变化结果,反演分析全球洋底板块运动特征.研究表明,板块汇聚边界、板块内无震海岭、海山群、断裂带等区域重力异常变化显著,而在板块离散边界无明显变化趋势;西南印度洋中脊、大西洋中脊、中印度洋中脊等地区重力异常垂直梯度变化显著,且在西太平洋俯冲带、部分海岭区域也存在明显变化,其空间分布与地形基本吻合.海洋重力场变化整体上准确反映了全球洋底板块构造运动.相较于重力异常变化反演结果,重力垂直梯度的变化能够更为准确地反映洋底板块运动特征,特别是在洋中脊区域,扩张速率越小,垂直重力梯度变化越显著.此外,详细讨论了测高海洋重力场不确定因素对洋底板块运动分析结果的影响,海面坡度改正是主要因素之一.  相似文献   

Simultaneous water and vapour transfer in an unsaturated mudstone in badlands terrain,southwestern Taiwan     

Kohei Higuchi  Masahiro Chigira  Der-Her Lee  Jian-Hong Wu 《地球表面变化过程与地形》2020,45(13):3323-3335

The simultaneous transfer of pore fluid and vapour was studied in the unsaturated shallow subsurface of a Plio-Pleistocene marine mudstone badland slope in southwestern Taiwan during the dry season using field monitoring data and numerical simulations. Data from field monitoring show mass-basis water contents of ~0.05 to ~0.10 that decrease towards the unsaturated ground surface and were invariant during the middle part of the dry season, except for daily fluctuations. In addition, the observed daily fluctuations in water content correlate with fluctuations in bedrock temperature, especially at depths of 2.5–5.0 cm. Periodic increases in water content occurred most notably during the day, when the bedrock temperature showed the greatest increase. Water contents then decreased to the previous state as bedrock temperature decreased during the night. Calculated vapour fluxes within the mudstone during the day increased up to 6 × 10⁻⁶–1 × 10⁻⁵ kg m⁻² s⁻¹, deriving a 0.01–0.02 increase in mass-basis water content at 2.5 cm depth for a 12-h period. This agrees with field monitoring data, suggesting that increases in water content occurred due to vapour intrusions into the bedrock. Pore water electrical conductivity (EC) showed periodic variations due to vapour intrusion, and gradually increased between the ground surface and depths of 2.5–5.0 cm. In contrast, pore water EC gradually decreased between 15 and 40 cm depth. Calculated water fluxes at depths of 2.5–40.0 cm varied from −4 × 10⁻⁶ to −2 × 10⁻⁹ kg m⁻² s⁻¹. These fluxes generated an increase in solute concentrations at the ground surface, with negative values of water flux indicating an upwards movement of water towards the surface. We show that the increase in solute content due to solute transfer from depth is highly dependent on variations in water flux with depth. © 2020 John Wiley & Sons, Ltd.  相似文献   

Runoff response of a small agricultural basin in the argentine Pampas considering connectivity aspects     

María Guadalupe Ares  Marcelo Varni  Celio Chagas 《水文研究》2020,34(14):3102-3119

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Characterizing spatial and temporal variation in 18O and 2H content of New Zealand river water for better understanding of hydrologic processes     

Jing Yang  Bruce D. Dudley  Kelsey Montgomery  Will Hodgetts 《水文研究》2020,34(26):5474-5488

Time series of hydrogen and oxygen stable isotope ratios (δ²H and δ¹⁸O) in rivers can be used to quantify groundwater contributions to streamflow, and timescales of catchment storage. However, these isotope hydrology techniques rely on distinct spatial or temporal patterns of δ²H and δ¹⁸O within the hydrologic cycle. In New Zealand, lack of understanding of spatial and temporal patterns of δ²H and δ¹⁸O of river water hinders development of regional and national-scale hydrological models. We measured δ²H and δ¹⁸O monthly, together with river flow rates at 58 locations across New Zealand over a two-year period. Results show: (a) general patterns of decreasing δ²H and δ¹⁸O with increasing latitude were altered by New Zealand's major mountain ranges; δ²H and δ¹⁸O were distinctly lower in rivers fed from higher elevation catchments, and in eastern rain-shadow areas of both islands; (b) river water δ²H and δ¹⁸O values were partly controlled by local catchment characteristics (catchment slope, PET, catchment elevation, and upstream lake area) that influence evaporation processes; (c) regional differences in evaporation caused the slope of the river water line (i.e., the relationship between δ²H and δ¹⁸O in river water) for the (warmer) North Island to be lower than that of the (cooler, mountain-dominated) South Island; (d) δ²H seasonal offsets (i.e., the difference between seasonal peak and mean values) for individual sites ranged from 0.50‰ to 5.07‰. Peak values of δ¹⁸O and δ²H were in late summer, but values peaked 1 month later at the South Island sites, likely due to greater snow-melt contributions to streamflow. Strong spatial differences in river water δ²H and δ¹⁸O caused by orographic rainfall effects and evaporation may inform studies of water mixing across landscapes. Generally distinct seasonal isotope cycles, despite the large catchment sizes of rivers studied, are encouraging for transit time analysis applications.  相似文献   

结合BM3D和多级非线性加权平均中值滤波的遥感影像混合噪声去噪方法     

任超  李现广  邓开元  潘亚龙  朱子林  张志刚  施显健 《测绘通报》2020,(1):89-93

提出了一种基于三维块匹配（BM3D）和多级非线性加权平均中值滤波的遥感影像混合噪声去噪方法，使用coief3小波和sym2小波替换传统三维块匹配算法中的bior1.5和hear参数，将三维块匹配算法和多级非线性加权平均中值滤波相结合以提高算法对混合噪声的去噪能力。进行一个仿真对比试验和一个真实遥感影像去噪试验，试验表明，本文提出的方法在遥感影像混合噪声去噪方面效果要优于传统混合噪声去噪方法。  相似文献   

无人机技术在海岛测绘中的应用     

李雪瑞  魏征  田松  李明杰 《测绘通报》2020,(1):150-153

为提高海岛测绘的技术手段，将无人机引入海岛地形调查中，以Swallow-P小型固定翼无人机开展惠州市大亚湾虎洲海岛大比例尺测图为例，系统归纳了无人机外业数据采集与内业数据处理的具体流程，并制作了DEM和DOM成果；经过实测地面点精度分析得出虎洲无人机大比例尺测图成果平面位置中误差和高程中误差符合1∶1000测图精度要求。  相似文献   

面向数字孪生城市的智能化全息测绘   总被引：2，自引：0，他引：2  

顾建祥  杨必胜  董震  杨常红 《测绘通报》2020,(6):134-140

以大数据、物联网、人工智能、虚拟现实、云计算、智能驾驶等新技术为代表的信息化浪潮席卷全球，数字世界与物理世界正形成两大平行发展、相互作用的体系，数字孪生技术应运而生。随着物联网技术（IOT）的发展，数字孪生的理念被引入到智慧城市建设中来，深刻影响着城市规划、建设与治理。笔者所在单位面向数字孪生城市和自然资源统一监管对测绘地理信息的新需求，在全国开创性地开展了面向数字孪生城市的智能化全息测绘试点工作。本文结合上海市智能化全息测绘试点工作，从数字孪生城市、数字孪生城市对地理信息的新需求、智能化全息测绘关键技术及测绘成果等方面展开了论述，重点介绍了智能化全息测绘的技术体系和产品体系，以及在社会各领域的应用成果。  相似文献   

运用GD-PBIBD编码的矢量空间数据数字指纹算法     

陈金萍  张黎明  蒋美容  王昊 《测绘通报》2020,(8):81

针对矢量空间数据叛逆者追踪难及编码效率低的问题，本文提出了一种运用GD-PBIBD码的指纹算法。首先运用GD-PBIBD构造指纹编码，将待嵌入指纹序列运用Logistic映射置乱，通过D-P算法提取矢量空间数据的特征点，对特征点实施DFT变换得到相位系数和幅度系数；然后运用QIM方法将指纹嵌入DFT变换域的幅度系数上；最后应用DFT逆变换得到含指纹的矢量空间数据。试验选取部分中国路网数据和某区域绿地数据，运用该算法嵌入指纹后，对其进行线性和非线性模拟攻击，成功提取指纹序列，利用汉明距离追踪出合谋者。该算法编码构造简单，在码长一定的情况下，较BIBD码可容纳更多的用户，效率高；算法抗单用户指纹攻击及多重攻击的稳健性较好，也能够抵抗多用户最小值和最大最小值攻击，追踪到所有叛逆者，可用于矢量空间数据版权保护，为矢量空间数据叛逆者追踪提供依据。  相似文献   

基于点云数据的不规则文物三维重建——以经幢为例     

喜文飞  李灵索  杨勇  李国柱  李春梅  李金平 《测绘通报》2020,(12):87-89

海量点云数据可以较好地构建文物的三维建模，针对文物复杂的表面结构，传统的算法很难达到精细建模，为了解决复杂模型表面的空间三角网构网问题，本文结合空间三角形的法向量构建三角网，以空间三角网表面的曲率为约束条件，构建物体表面的空间三角网，然后对构建的空间三角网进行精细建模。以昆明市文物——经幢为例进行三维重建试验，结果表明，新方法适合室内文物的三维建模，可以达到较好的效果。  相似文献