共查询到20条相似文献，搜索用时 171 毫秒
1.
From the analysis and the contrast of band-limited ray tracing method based on Kirchhoff integral,it was found that the method performs many approximations in the derivation process and omits the derivative term of the phase factor in the Kirchhoff integral. Numerical calculations and analysis show that the omission of correlation terms in Kirchhoff integrals has a non-negligible effect on the calculation results,and the different terms in the Kirchhoff integral have different effects on different frequency ranges. The method can be applied to velocity models containing complex interfaces without changing the velocity model and can be extended to elastic waves and continuous media. 相似文献
2.
Prestack elastic reverse time migration ( RTM) requires multicomponent seismic data .But for multi-component elastic Kirchhoff migration , there is a limitation that ray theory no longer applies if thegeology be-comes complicated .In this paper, the authors have created a new 2D migration context for isotropic , elastic RTM, which included decomposition of the elastic source and receiver wavefields into P and S wave vectors by decoupled elastodynamic extrapolation , which retained the same stress and particle velocity components as the input data .Then we appliedsource-normalized crosscorrelation imaging condition in elastic reverse time migra-tion to compensate the energy of deep strata .We found that the resulting images were nearly identical to the ve-locity model , and the resolution has been improved .Our method is a wavefielddecomposition based on vector , and we can alsoavoid the problem of polarity reversal of converted shear wave imaging .It proved the applicabili-ty of the method proposed in our paper . 相似文献
3.
Kirchhoff beam migration is a beam migration method, which focuses on rapid imaging of geological structures. Although this imaging method ignores the amplitude information in the calculation process, it can calculate multi-arrival traveltime. This migration method takes into account both imaging accuracy and computational efficiency. Kirchhoff beam migration employs coarse grid techniques in several key steps such as traveltime calculation, weight function calculation, and imaging calculation. The selection of the coarse mesh size has an important influence on the computational efficiency and imaging accuracy of the migration imaging method. This paper will analyze this influence and illustrate the analysis results by the Marmousi data sets. 相似文献
4.
《中国海洋大学学报(英文版)》2019,(6)
This paper introduces an internal multiple prediction method based on imaging profile prediction and Kirchhoff demigration. First, based on an inputted prestack time migration profile, the method predicts the prestack time migration profile that only includes internal multiples by inverse scattering series method. Second, the method uses velocity-weighted Kirchhoff demigration to create shot gathers that contains only internal multiples. Internal multiple prediction based on the prestack time migration profile effectively reduces the computational cost of multiple predictions, and the internal-multiple shot gathers created by Kirchhoff demigration remarkably reduces the complexity of the practical problem. Internal multiple elimination can be conducted through the combined adaptive multiple subtraction based on event tracing. Synthetic and field data tests show that the method effectively predicts internal multiples and possesses considerable potential in field data processing, particularly in areas where internal multiples develop seriously. 相似文献
5.
利用差分测速和Kalman滤波估计相位变率方法对某次航空重力测量的飞行数据进行了解算,通过与GT-1A自带的GPS高精度定位测速软件和WAY-Point软件比对分析,结果表明：采用Kalman滤波估计相位变率的GPS差分测速,能够适应较复杂的运动模式,定速精度达到mm/s级,高于WAY-Point软件的动态测速精度。 相似文献
6.
In the framework of 3D potential flow theory, Bessho form translating-pulsating source Green’s function in frequency domain is chosen as the integral kernel in this study and hybrid source-and-dipole distribution model of the boundary element method is applied to directly solve the velocity potential for advancing ship in regular waves. Numerical characteristics of the Green function show that the contribution of local-flow components to velocity potential is concentrated at the nearby source point area and the wave component dominates the magnitude of velocity potential in the far field. Two kinds of mathematical models, with or without local-flow components taken into account, are adopted to numerically calculate the longitudinal motions of Wigley hulls, which demonstrates the applicability of translating-pulsating source Green’s function method for various ship forms. In addition, the mesh analysis of discrete surface is carried out from the perspective of ship-form characteristics. The study shows that the longitudinal motion results by the simplified model are somewhat greater than the experimental data in the resonant zone, and the model can be used as an effective tool to predict ship seakeeping properties. However, translating-pulsating source Green function method is only appropriate for the qualitative analysis of motion response in waves if the ship geometrical shape fails to satisfy the slender-body assumption. 相似文献
7.
为准确反演勘察孔地层岩性信息、提高岩屑反演勘察孔地层岩性的准确性, 依托某隧道水平定向钻地质勘察项目, 开展了水平定向钻隧道地质勘察孔岩屑运移与地层相关性研究。研究结果表明: 依据岩屑运移速度、费祥俊临界流速理论和Larsen最小返速理论对现场岩屑运移形式的分析, 推知不同围岩岩屑颗粒在水平定向钻孔环空内的运移形式以推移为主, 少部分悬移, 且存在少量岩屑床; 在水平定向钻勘察工程现场, 钻头处产生的地层岩屑最先以悬浮运移状态随泥浆返出; 基于物料输送相关理论分析岩屑颗粒自由悬浮和运动方程, 建立了水平定向钻勘察孔岩屑悬移运移模型; 依托现场碳质板岩和石英片岩相关参数进行了岩屑运移与地层相关性分析, 分别得出完整地层和断层破碎带的岩屑运移孔壁阻力系数, 且断裂带处岩屑运移孔壁阻力系数约为非断裂带处的2.72倍; 得出不同直径钻杆工作范围内的钻孔环空岩屑最终悬浮运移速度, 建立了岩屑运移与地层的关联分析计算模型。研究结果为准确反演勘察孔地层岩性信息, 以及后续隧道的顺利施工提供了理论和数据支持。 相似文献
8.
XUE Meiqi LIU Sixin LU Qi LI Hongqing WANG Yuanxin CHANG Xinghao RAN Limin ZHAO Yonggang LI Jianwei 《世界地质(英文版)》2021,24(2):103-110
The authors use the common offset ground penetrating radar(GPR) data inversion based on ray theory to estimate interval velocity and to obtain the relative permittivity. In the ray-tracing based inversion, the input data are the offset distance between antennas, the velocity of the first layer, the pick-up amplitude and re-ference amplitude of each reflection layer. The thickness and velocity of each layer are calculated by this recursive method. Firstly, the horizontal homogeneous layered medium model is established, and the ideal inversion results are obtained. Subsequently, Monte Carlo method is used to establish a randomly undulating homogeneous layered medium model. The common offset GPR data for the built geological model is then simulated by finite-difference time-domain(FDTD). It proved that this ray-tracing based inversion method is feasible for the horizontal layered geological model, even the layered geological model with random undulation. Undulation, represented by RMS height and CL(correlation length), influences the inversion results. Finally, a more complex geological model--pinch-out model was established. In the pinch-out model, the pinch-out interface can be clearly identified, though there is a false anomaly, which will not significantly affect the identification of the underground medium structure. 相似文献
9.
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?????????е???α????????????????λ?????????????????????????????????λ?仯???ɡ?????????????????ж?????????????????????????????α?λ?????н??е??????????GM(1,1)?????????????????????÷??????????????????????÷??????????????GM(1,1)?????????????Ч??????????????? 相似文献
10.
使用搭载200&400 MHz复合天线的LTD系列探地雷达,对埋设的未爆弹进行探测试验,并运用克希霍夫积分偏移法及三维插值算法对探地雷达数据进行三维成像。试验结果能准确地反映出浅埋未爆弹的位置信息,可指导排爆人员进行精确的开挖及排除。 相似文献
11.
地下采煤会引起地表沉降、变形,甚至引发山体、河堤滑坡等地质灾害。采动坡体的稳定性研究一直是采矿工程中实际关心的问题。该文首先介绍分析了概率积分法移动变形稳态、动态预测模型以及基于极限平衡理论的单滑面采动坡体稳定性预测模型,提出了使用概率积分法结合Knothe时间函数对采动坡体稳定性进行预测分析的方法,并使用C#及XML Schema语言编制了相关的计算程序。最后,结合一个工程实例对采动坡体稳定性和动态变化过程进行了预测与分析,通过实测数据验证了提出方法的可行性,得出了采动引起的坡体下沉是影响坡体稳定性的主要因素,并提出了在坡体拉伸阶段进行注浆加固的方法。 相似文献
12.
本文提出定时观测整数风资料正确地用于大气稳定度分类的1/2计数修正方案,成都、重庆各十年的统计结果表明:该修正方案的统计结果与国家标准规定的自记风统计结果十分吻合,从而使整数风速能替代自记风速用于大气稳定度统计,而不带来多大误差。 相似文献
13.
Seismic wave modeling is a cornerstone of geophysical data acquisition, processing, and interpretation, for which finite-difference methods are often applied. In this paper, we extend the velocity-pressure formulation of the acoustic wave equation to marine seismic modeling using the staggered-grid finite-difference method. The scheme is developed using a fourth-order spatial and a second-order temporal operator. Then, we define a stability coefficient (SC) and calculate its maximum value under the stability condition. Based on the dispersion relationship, we conduct a detailed dispersion analysis for submarine sediments in terms of the phase and group velocity over a range of angles, stability coefficients, and orders. We also compare the numerical solution with the exact solution for a P-wave line source in a homogeneous submarine model. Additionally, the numerical results determined by a Marmousi2 model with a rugged seafloor indicate that this method is sufficient for modeling complex submarine structures. 相似文献
14.
借鉴选权拟合思想,对区域地壳运动的整体旋转和线性应变模型中欧拉矢量部分附加不等式约束,将区域地壳运动的欧拉参数约束到由多年观测资料确定的平均欧拉参数值附近,建立附有不等式约束的整体旋转和线性应变模型。对中国大陆构造环境监测网络在环渤海区域的近几期GPS观测速度场数据进行拟合分析,结果表明,本文方法通过不等式约束可适当增强块体整体运动趋势的平滑性,获得对速度场更高的拟合精度,可进一步增强模型的物理解释能力。 相似文献
15.
To study the bubble plume’s seismic response characteristics, the model of a plume water body has been built in this article using the bubble-contained medium acoustic velocity model and the stochastic medium theory based on an analysis of both the acoustic characteristics of a bubble-contained water body and the actual features of a plume. The finite difference method is used for forward modelling, and the single-shot seismic record exhibits the characteristics of a scattered wave field generated by a plume. A meaningful conclusion is obtained by extracting seismic attributes from the pre-stack shot gather record of a plume. The values of the amplitude-related seismic attributes increase greatly as the bubble content goes up, and changes in bubble radius will not cause seismic attributes to change, which is primarily observed because the bubble content has a strong impact on the plume’s acoustic velocity, while the bubble radius has a weak impact on the acoustic velocity. The above conclusion provides a theoretical reference for identifying hydrate plumes using seismic methods and contributes to further study on hydrate decomposition and migration, as well as on distribution of the methane bubble in seawater. 相似文献
16.
《世界地质(英文版)》2016,(1)
When using borehole sensors and microseimic events to image,spatial aliasing often occurred because of the lack of sensors underground and the distance between the sensors which were too large. To solve the aliasing problem,data reconstruction is often needed. Curvelet transform sparsity constrained inversion was widely used in the seismic data reconstruction field for its anisotropic,multiscale and local basis. However,for the downhole case,because the number of sampling point is much larger than the number of the sensors,the advantage of the curvelet basis can't perform very well. To mitigate the problem,the method that joints spline and curvlet-based compressive sensing was proposed. First,we applied the spline interpolation to the first arrivals that to be interpolated. And the events are moved to a certain direction,such as horizontal,which can be represented by the curvelet basis sparsely. Under the spasity condition,curvelet-based compressive sensing was applied for the data,and directional filter was also used to mute the near vertical noises. After that,the events were shifted to the spline line to finish the interpolation workflow. The method was applied to a synthetic model,and better result was presented than using curvelet transform interpolation directly. We applied the method to a real dataset,a microseismic downhole observation field data in Nanyang,using Kirchhoff migration method to image the microseimic event. Compared with the origin data,artifacts were suppressed on a certain degree. 相似文献
17.
In conventional seismic exploration,complex overburden prevents us from imaging the deeper under- ground structure,because near-surface velocity model cannot be efficiently simplified and accurately estab- lished． The virtual source method provides a promising solution,which images below a complex overburden without the knowledge of overburden velocities and near-surface changes． In this paper,the authors simulate the forward modeling under complex overburden with sources on the surface and receivers in the horizontal well, and reset the real sources into the horizontal well using the virtual source method,which subtly avoid the distor- tion effects of the complex overburden． Finally the underground structure can be imaged using Kirchhoff migra- tion,so the feasibility and advantages of the virtual source method are verified． 相似文献
18.
岩性识别作为人工智能和大数据在地质工程细分领域的实践应用方向, 可以为相关人员野外地质工作提供有效助力。为了更好地促进岩性识别在专业领域的应用, 通过对巢湖北部山区的岩石图像采集、数据预处理、迁移学习、网络搭建、网络训练及模型测试等步骤, 实现了基于岩石图像的大数据深度学习识别; 并在归纳总结前人工作的基础上, 提出了多尺度岩性识别方法。根据岩石细观图像建立多尺度模型并赋予一定权重, 与岩石识别模型共同识别得到综合结果, 对岩石岩性整体识别的同时兼顾局部纹理、粒径等细观信息。研究结果表明, 本模型对岩石识别的适用性强, 多尺度方法对于提高识别结果的正确率具有一定的帮助, 模型的测试正确率达到95%以上, 能很好地识别岩石岩性。 相似文献
19.
随着勘探程度的提高, 小型复杂断块圈闭已成为当前凸起区油气勘探的重点领域, 为了明确辽西凸起断块圈闭油气差异富集的原因, 利用三维地震、测录井、薄片等数据资料, 通过三维流线定量模拟的方法, 分析凸起斜坡区潜山顶面风化壳特征, 建立"壳-断"耦合油气运移模式, 刻画斜坡区油气优势运移路径, 从而明确风化壳运移对凸起断块油气差异富集的控制作用。结果表明: ①研究区潜山历经多期构造运动, 且潜山岩性主要为下古生界碳酸盐岩和太古界花岗岩, 岩性性质较脆, 易被风化剥蚀, 风化壳溶蚀孔隙及构造裂缝普遍发育, 且分布稳定, 形成斜坡区油气侧向长距离运移的主要通道; ②斜坡中带受反向断层控制形成断隆构造, 油气沿风化壳的运移受斜坡断隆带遮挡, 形成"壳-断"耦合油气运移模式, 断隆带断距大小控制风化壳油气侧向运移能力; ③利用三维流线定量模拟的方法, 刻画出研究区四级油气优势运移通道, 明确不同级别油气运移通道对凸起断块油气富集程度的控制作用。该研究成果有效指导辽西凸起油气勘探实践, 并填补了富油凹陷成熟凸起区油气成藏认识及研究方法。 相似文献
20.
A methodology for estimating Leaf Area Index by assimilating remote sensing data into crop model based on temporal and spatial knowledge 总被引：1，自引：0，他引：1
In this paper,a methodology for Leaf Area Index(LAI) estimating was proposed by assimilating remote sensed data into crop model based on temporal and spatial knowledge.Firstly,sensitive parameters of crop model were calibrated by Shuffled Complex Evolution method developed at the University of Arizona(SCE-UA) optimization method based on phenological information,which is called temporal knowledge.The calibrated crop model will be used as the forecast operator.Then,the Taylor′s mean value theorem was applied to extracting spatial information from the Moderate Resolution Imaging Spectroradiometer(MODIS) multi-scale data,which was used to calibrate the LAI inversion results by A two-layer Canopy Reflectance Model(ACRM) model.The calibrated LAI result was used as the observation operator.Finally,an Ensemble Kalman Filter(EnKF) was used to assimilate MODIS data into crop model.The results showed that the method could significantly improve the estimation accuracy of LAI and the simulated curves of LAI more conform to the crop growth situation closely comparing with MODIS LAI products.The root mean square error(RMSE) of LAI calculated by assimilation is 0.9185 which is reduced by 58.7% compared with that by simulation(0.3795),and before and after assimilation the mean error is reduced by 92.6% which is from 0.3563 to 0.0265.All these experiments indicated that the methodology proposed in this paper is reasonable and accurate for estimating crop LAI. 相似文献