共查询到19条相似文献，搜索用时 562 毫秒
1.
基于磁导率的频率域航空电磁法双频反演方法 总被引：1，自引：0，他引：1
以往的频率域航空电磁法数据反演方法中,通常在模型中以真空磁导率代替介质磁导率,忽略了磁性层影响。但在高磁性区域,这样做将会导致计算电阻率值偏高。针对这一问题,首先根据层状介质模型研究了考虑磁导率和电阻率因素条件下的电磁场正演计算方法,并且分析了不同磁性介质对频率域电磁响应的影响规律。在此基础上,提出了磁导率和电阻率的双频反演方法,电阻率是通过2个频率的虚分量之比计算得到的,计算结果更加可靠,提高了磁性区域视电阻率填图的精度。通过对模型计算和实测数据进行反演计算,表明这种方法具有较高的反演精度,为强磁性区域航空电磁法视电阻率填图提了供一种行之有效的反演方法。 相似文献
2.
《物探化探计算技术》2020,(3)
探地雷达反演问题是高度非线性的,采用线性反演方法往往难以获得较好的反演效果,因此提出了将生物地理学优化算法同粒子群优化算法相结合的混合非线性反演方法。将该方法用于探地雷达时间域波形反演,采用时间域有限差分方法进行正演,以信号的均方误差函数作为目标函数,并针对波形反演的特点,在目标函数中加入波形的导数拟合差作为约束项,实现了结构层厚度和介电常数的波形反演。对比经典粒子群算法和生物地理学优化算法在多层介质仿真数据的一维波形反演中的效果,验证了该改进算法的有效性和抗噪性。 相似文献
3.
时间域航空电磁数据加权横向约束反演 总被引：3，自引：0，他引：3
传统的单点一维反演技术处理时间域航空电磁数据得到的电阻率和层厚度容易呈现横向不连续性,导致层界面不光滑。即使相邻测点的反演结果也会出现突变现象,与实际地质情况不符,给解释工作带来困难。笔者针对时间域航空电磁数据空间采样密集、在沉积岩地区工作时地下电性结构横向连续性较好的特点,研究了时间域航空电磁数据参数加权横向约束反演方法。反演时同时考虑数据拟合、相邻测点电阻率和层厚度横向约束以及深度横向约束,利用参数加权来调整对各层模型参数和深度横向光滑度的约束强度。通过对理论和实测数据反演并与传统的单点一维反演结果进行对比,验证了拟二维横向加权约束反演是处理时间域航空电磁数据的有效方法。横向约束反演结果电阻率和层厚度横向光滑连续,层界面清晰。引入参数加权实现对不同参数横向光滑度和连续性的制约,可进一步提高反演解的稳定性。加权因子对反演结果有较大影响,在实际应用中,应该综合考虑地质资料选择合适的加权因子。 相似文献
4.
反演问题一直是地球物理的重点研究问题之一。本文以长导线源半航空瞬变电磁为例,对时间域半航空数据进行一维反演研究。将自适应正则化(ARIA)反演方法和阻尼最小二乘(LM)反演方法相结合,提出一种改进的反演方法:自适应正则化-阻尼最小二乘(ARIA-LM)反演算法。本文选用三层理论模型对比阻尼最小二乘算法、自适应正则化反演算法与本文方法,并使用四层理论地层模型来验证算法的有效性和可靠性。结果表明:该算法在一定程度上对高阻分辨率增强,能有效提高反演的精度及稳定性。 相似文献
5.
6.
《物探化探计算技术》2017,(1)
半航空时间域电磁法集成了地面和航空电磁法各自的优势,不仅容易实现大发射磁矩,增大勘探深度,同时还可以提高勘探效率。但是由于半航空时间域电磁法在测量过程中,收、发距会发生变化,因此与地面和航空电磁法相比,其数据处理与反演解释更加困难。以长导线电性源半航空电磁法为例,将自适应正则化反演算法应用于半航空时间域电磁数据反演中。首先给出最平缓模型约束条件下的半航空时间域电磁数据自适应正则化反演算法,并引入并行技术实现了该反演算法的并行计算;然后对两种三层地电模型和一种六层地电模型的理论电磁响应加高斯白噪声后的数据进行反演计算;最后对其反演结果和并行计算的效率进行了详细地分析与讨论。实验结果分析表明:自适应正则化反演算法是一种有效的半航空时间域电磁数据反演解释方法,该方法具有很好的收敛性和稳定性;自适应正则化反演算法并行计算能大大减少反演计算时间,提高反演效率。 相似文献
7.
海洋TEM中心回线装置一维正演及全时域视电阻率计算 总被引：1，自引：0，他引：1
首先对海洋中深海区中心回线装置的瞬变电磁响应进行了一维正演计算,频率域垂直磁场分量表达式中的汉克尔积分变换采用了124点滤波系数进行数值计算;时—频域转换使用了适应时间范围较宽的余弦变换算法;然后采用连分式算法求取了典型地电模型全时域视电阻率随深度变化的曲线。结果表明,曲线基本可以反映地下电性介质的相对大小变化;并且,根据极值点可以大致确定低阻或高阻层顶界面深度。这为海洋TEM实测资料的快速定性解释以及反演初始模型参数的选定打下了基础。 相似文献
8.
《物探与化探》2015,(6)
在电磁探测理论中,电导率和磁导率是两个重要的岩石物性参数。在磁性较强的地区进行大地电磁探测工作时,电磁场信号必然受到介质磁性的影响。将磁化率参数引入到二维大地电磁正演理论中,实现了含磁化率的大地电磁有限单元法数值模拟。建立棱柱体模型计算并分析了磁化率参数对大地电磁的电场、磁场、视电阻率及相位等参数的影响。数值模拟结果表明:高磁性介质导致电场升高,磁场降低,视电阻率增大,相位复杂变化,且随着磁性物质的增多或磁化率的增大,这种影响逐渐变大。引入电导率、磁化率光滑约束与磁化率对数约束,采用改进的特别快速模拟退火法实现了电阻率、磁化率参数一维同时反演。对K型、H型中间层高磁地电模型进行反演试算,反演结果良好。该研究为在高磁性地区开展大地电磁工作提供了基础,对实现"第二找矿空间"内的矿产勘探,具有一定的意义。 相似文献
9.
新疆色尔特能地区视密度和视磁性的反演 总被引：1，自引：0，他引：1
将起伏地形上测量的重力异常和磁异常,延拓至平均水平面;对平面上的场进行不同深度层源的切割分离;再将各层的场向下延拓至相应的深度,并反演出该深度层的密度和磁化强度结构。以此得到的密度和磁化强度,反映该深度层密度和磁性的近似分布,称为视密度和视磁性反演。本方法反演速度很快,在主频1.73 GHz的微机上,完成71×81数据点反演的计算时间为10s。这里以新疆色尔特能地区的实例说明这种方法的反演效果。 相似文献
10.
频率测深中磁性层的视电阻率响应 总被引：1，自引：0，他引：1
频率测深理论曲线现有的计算公式都是把各层介质的磁导率看成等于真空磁导率μ_0的情况推演出来的,这对沉各岩层通常适宜的。但还有一些磁性岩层(铁磁性矿床或基性火成岩)其磁导率将导致频率测深视电阻率值的增高。从这点出发,文中就频率测深中磁性层的视电阻率响应进行了理论公式的推导和实算。结果表明:磁性层对频率测深视电阻率曲线的影响是不可忽视的,在频率测深方法中利用磁导率来探测磁性层是可行的。 相似文献
11.
目前有限元技术的开发及在电磁勘查技术中的应用已日趋成熟.然而,有限元正演模拟主要集中于地面和海洋电磁,航空电磁三维有限元模拟尚没有受到足够重视.以前人工作为基础,利用结构化网格实现了航空电磁系统的三维矢量有限元正演模拟.从二次场双旋度矢量非齐次亥姆霍兹方程出发,应用广义变分原理推导出变分方程,并采用六面体单元剖分,将场置于单元棱边上,对每个单元应用线性插值,最后合成含有稀疏矩阵的线性方程组.针对航空电磁多源性问题,利用MUMPS(multifrontal massively parallel sparse direct solver)直接求解器进行求解,在保证精度的前提下大幅度提高计算速度.利用单个异常体模型检验算法的精度和软件的稳定性,进而通过典型地电模型的模拟验证算法的有效性.对不同地下电性结构正演模拟结果进行对比分析,进一步研究了覆盖层和垂直接触带等典型构造对航空电磁响应的影响特征. 相似文献
12.
Mineral exploration in regolith-dominated environments is challenging, requiring the development of new technical tools and approaches. When airborne electromagnetics (AEM) is combined with information on stratigraphy, mineralogy, geochemistry, drilling and landscape observations in a geological context, it becomes a powerful approach to describe the architecture of the regolith cover. This has significant implications for mineral exploration in any regolith-dominated terrain (RDT). This research presents two case studies of AEM data, integrated in a geological context for mineral exploration in the Yilgarn craton margin/Albany–Fraser Orogen (AFO).In one of the study sites presented (study site 1: Neale tenement), the availability of AEM data allowed for lateral and vertical extrapolation of the information contained in datasets at specific locations, thereby creating a 2D architectural model for the regolith cover. In addition, it was determined: (1) the total thickness of the regolith cover and its variability (between 2 m and ~ 65 m); (2) that low conductivity transported overburden and silcrete units, with a total thickness between ~ 5 and 45 m, is widely distributed, capping the upper saprolite; and (3) that the silcrete unit varies laterally from being completely cemented to permeable, and that these permeable areas (“windows”) coincide vertically with mineralogical/textural/moisture/salt content changes in the underlying saprolite, resulting in increased conductivity. This has been interpreted as resulting from more intense vertical weathering, and consequently a higher vertical geochemical dispersion of the basement signature towards surface. AEM has been used to assist in identifying and describing the lateral continuity of these “windows” in areas with no direct field observations. Surface geochemical sampling above these permeable areas may deliver more reliable geochemical basement signatures.In the second study site (Silver Lake tenement) the AEM data was strongly influenced by the high conductivity of the hypersaline groundwater. This had a significant effect on the AEM response, resulting in reduced depth penetration and reduced resolution of subtle conductivity contrasts between cover units. Despite this, the AEM data set, combined with geological observations in the area, was able to map the presence and extent of a buried palaeochannel network, the most significant architectural sedimentary feature in the cover. This interpretation allowed for a more efficient drilling campaign to be designed to sample the fresh basement rock suites in the area, by avoiding drilling into palaeochannels.Integrated and constrained by the geological context, the application of AEM conductivity models by geologists is envisioned as one of the most promising tools within the exploration geologist toolbox to understand the architecture of the cover. 相似文献
13.
Aerial electromagnetic exploration obtains the ground resistivity of a wide area by measuring the intensity of a secondary magnetic field induced in the ground by a primary magnetic field. We conducted the AEM exploration in the Yamakoshi Village where was dameged by the Mid Niigata Prefecture Earthquake in 2004, for the landslide hazard assessment. The apparent resistivity distribution in the survey area differ between the Imogawa River Basin and the Asahigawa River Basin, and the former shows high resistivity and the later shows low resistivity with 30 -m as the boundary. In the high resistivity zone that corresponds to the sandy rock distribution area, the large landslide blocks show lower resisitivity than in the surrounding ground. In sandy rock distribution areas, it is possible for the relatively low resistivity parts to be an index of the instability of slopes, even in landslide blocks where deformation has not yet appeared. 相似文献
14.
We demonstrate that the approximate source kinematics of the San Fernando, 1971 earthquake can be back-predicted by analysing its macroseismic intensity data set (felt reports) objectively and quantitatively. This is done by inverting either the data set of the intensity values observed in all sites, or the intensities tessellated with the Voronoi polygons technique. It is shown that the kinematic characteristics found following our method (epicentral coordinates, source depth, seismic moment, rupture length, Mach number, fault plane solution) match those determined by other authors, via instrumental measurements, rather well. The prerequisite for obtaining these results is that local amplification must not affect groups of neighboring sites. It was possible to invert the U.S.G.S. ``felt reports' for the source because this data set is sufficiently uncontaminated by local site responses, and retains relevant regional traces of source effects. Isoseismal maps cannot be safely used for this task, because qualitative drawing criteria give subjective results. Isoseismals, based on incomplete space frequency samplings, give rise to spurious effects, whereas the Voronoi polygons produce easy-to-grasp, quantitative and objective, representations of macroseismic intensity data. The tests performed, up to now on a series of earthquakes, suggest that the combined use of tessellation and of our KF model is promising mostly for inverting intensities of preinstrumental earthquakes. 相似文献
15.
航空电磁法筛选金属矿异常技术研究 总被引：2，自引：0，他引：2
[摘 要] 航电异常筛选是把航电基岩导体异常选出来进行编录和推断解释,把人文导体、气流扰
动、飞机剧烈动作、复盖层导体等引起的干扰和假异常剔除掉。本文基于国内完全自主研发的HDY-
402 三频航空电磁测量系统及方法技术,对典型模型进行计算,总结了三频航电的异常响应变化规律。
重点介绍了金属矿航电基岩导体异常、干扰异常的基本特征和异常筛选步骤。实践证明,只有充分认识
航电异常的基本特征,合理选择筛选步骤,航电异常筛选才能具有有效性和科学性,从而提高优选的矿
化有望异常的可靠性。 相似文献
16.
We present a new Bayesian framework for the validation of models for subsurface flows. We use a compositional model to simulate CO2 storage in saline aquifers, comparing simulated saturations to observed saturations, together with a Bayesian analysis, to refine the permeability field. At the laboratory scale, we consider a core that is initially fully saturated with brine in a drainage experiment performed at aquifer conditions. Two types of data are incorporated in the framework: the porosity field in the entire core and CO2 saturation values at equally spaced core slices for several values of time. These parameters are directly measured with a computed tomography scanner. We then find permeability fields that (1) are consistent with the measured parameters and, at the same time, (2) allow one to predict future fluid flow. We combine high performance computing, Bayesian inference, and a Markov chain Monte Carlo (McMC) method for characterizing the posterior distribution of the permeability field conditioned on the available dynamic measurements (saturation values at slices). We assess the quality of our characterization procedure by Monte Carlo predictive simulations, using permeability fields sampled from the posterior distribution. In our characterization step, we solve a compositional two-phase flow model for each permeability proposal and compare the solution of the model with the measured data. To establish the feasibility of the proposed framework, we present computational experiments involving a synthetic permeability field known in detail. The experiments show that the framework captures almost all the information about the heterogeneity of the permeability field of the core. We then apply the framework to real cores, using data measured in the laboratory. 相似文献
17.
The majority of known coalbed methane (CBM) production worldwide comes primarily from high-abundance CBM-enrichment areas or ‘fairways.’ The high-abundance CBM-enrichment areas are primarily characterised by large CBM resources with high single-well productions. CBM accumulation areas from the medium- to high-rank coals in the southern Qinshui Basin and the Hancheng CBM fields in the Ordos Basin were investigated based on regional geological analyses and physical analogue experiments. The results show that gas contents in the study areas increase with depths over the range from approximately 300 to 800 m, while permeabilities generally decrease with depths. Intervals with optimal gas content and permeability exist at a moderate depth along an inclined coal seam under the coupled control of temperature and stress. Brittle–ductile transition deformation increases the permeability and the pore-specific surface areas of coals. The gas content and permeability of the CBM reservoirs are shown to be two key factors determining the formation of high-abundance CBM areas. The coupling of gas enrichment and high permeability provides a favourable combination for CBM accumulation and high production. Combining CBM exploration and development practices in the study areas with physical analogue experiments, two CBM-enrichment models for medium- to high-rank coal have been recognised for different geological conditions, including (1) the model controlled by the depth in the slope zone and (2) the model controlled by the coal brittle and ductile in the deformation zones. 相似文献
18.
利用共轭梯度方法的激发极化三维快速反演 总被引：2，自引：0，他引：2
利用共轭梯度方法实现了激发极化(IP)三维快速反演。首先,利用共轭梯度方法反演电位数据,得到地下的三维电阻率模型,(由于避免了直接求偏导数矩阵,因此反演计算速度很快。)然后,以此电阻率模型为地下电导率分布,再反演IP数据得到三维极化率分布理论模型。试算结果表明其效果较好。 相似文献
19.
《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》1999,24(10):855-860
In regolith-dominated terrains, the nature of contemporary processes and the surface distribution of regolith materials may be a poor guide to the character and history of regolith materials at depth. The nature of regolith materials at depth is often critical to unravelling the development of a landscape. Conventional mapping aids such as air photos, multispectral remote sensing and airborne radiometrics are not wholly adequate in this context, as they penetrate limited depths (<0.4 m). Airborne electromagnetics (AEM) on the other hand, has the potential to map regolith materials to considerable depths (>100m).The application of AEM to regolith mapping and its potential as a tool in geomorphology are illustrated by reference to an AEM survey flown at Lawlers in the Yilgarn Craton of Western Australia. At Lawlers, AEM identifies a palaeochannel that has no surface expression. It cannot be seen in images of the Landsat, airborne radiometric or airborne magnetic data. The disposition of this channel in the landscape, and in particular its association with ferruginous materials forming breakaways, suggest that inversion of relief has been a significant factor in the evolution of the Lawlers landscape.The AEM data at Lawlers have also been used to map the weathering front. The topography of the weathering front not only reflects the movement of water through the landscape in a general sense, but also reflects the influence of lithology and structure. Different lithologies are clearly weathering to different depths. Information on the nature of the weathering front is potentially an important constraint on models of groundwater flow, and by association, models of solute dispersion. 相似文献