The recent proliferation of the 3D reflection seismic method into the near-surface area of geophysical applications, especially in response to the emergence of the need to comprehensively characterize and monitor near...The recent proliferation of the 3D reflection seismic method into the near-surface area of geophysical applications, especially in response to the emergence of the need to comprehensively characterize and monitor near-surface carbon dioxide sequestration in shallow saline aquifers around the world, justifies the emphasis on cost-effective and robust quality control and assurance （QC/QA） workflow of 3D seismic data preprocessing that is suitable for near-surface applications. The main purpose of our seismic data preprocessing QC is to enable the use of appropriate header information, data that are free of noise-dominated traces, and/or flawed vertical stacking in subsequent processing steps. In this article, I provide an account of utilizing survey design specifications, noise properties, first breaks, and normal moveout for rapid and thorough graphical QC/QA diagnostics, which are easy to apply and efficient in the diagnosis of inconsistencies. A correlated vibroseis time-lapse 3D-seismic data set from a CO2-flood monitoring survey is used for demonstrating QC diagnostics. An important by-product of the QC workflow is establishing the number of layers for a refraction statics model in a data-driven graphical manner that capitalizes on the spatial coverage of the 3D seismic data.展开更多
迹线是节理与岩体临空面相交形成的空间曲线,其几何形态直接反映岩体的结构特征。因此,快速准确地提取迹线信息具有重要的理论意义和工程价值。目前,基于空间点云数据的迹线提取多基于曲率开展,较少考虑点云的色彩信息,加之空间点云数...迹线是节理与岩体临空面相交形成的空间曲线,其几何形态直接反映岩体的结构特征。因此,快速准确地提取迹线信息具有重要的理论意义和工程价值。目前,基于空间点云数据的迹线提取多基于曲率开展,较少考虑点云的色彩信息,加之空间点云数量庞大,精度与效率均不理想。鉴于此,提出了一种新的基于降维投影的迹线提取方法(a new trace line extraction method based on dimensionality reduction projection,简称NTDR)。该方法将三维点云保形投影到二维平面,基于二维点云颜色信息进行高效边缘检测,结合三维点云的曲率及距离等几何特征进行聚类连线,实现了节理迹线的自动提取。研究表明:(1)相比于人工提取方法,NTDR处理大规模点云数据的时间节省了约91.07%,大幅提升了提取效率;(2)NTDR提取的迹线与人工提取相比,重合率达90.42%,且局部细节更多,在效果、精度上具有优越性;(3)NTDR在20%的噪点干扰下能保持80%以上的识别正确率,受噪点影响小;(4)相比于同类自动化迹线提取方法,NTDR在提取效果上有优势,更符合岩体实际的迹线分布情况。该方法可提升地质灾害预测效率,为隧道支护设计及工程安全评估提供数据支撑。展开更多
The effect of the azimuthal angle φ of the wave vector k on the propagation characteristics of the superluminous L-O mode waves （together with a case of the R-X mode） during different geomagnetic activities using a...The effect of the azimuthal angle φ of the wave vector k on the propagation characteristics of the superluminous L-O mode waves （together with a case of the R-X mode） during different geomagnetic activities using a three-dimensional （3D） ray-tracing method is investigated. This work is primarily an extension of our previous two-dimensional study in which the wave azimuthal angle was not considered. We present numerical simulations for this mode which is generated in the source cavity along a 70° night geomagnetic field line at the specific altitude of 1.5RE （where RE is the Earth＇s radius）. It is found that, as in the two-dimensional case, the trajectory of L-O mode starting in the source meridian plane （or the wave azimuthal angle φ = 180°） can reach the lowest latitude; whereas it basically stays at relatively higher latitudes starting off the source meridian plane （or φ=180°）. The results reveal that under appropriate conditions, the superluminous L-O mode waves may exist in the radiation belts of the Earth, but this remains to be supplemented by observational data.展开更多
基金supported by the U.S. Department of Energy (No. DE-FC26-03NT15414)
文摘The recent proliferation of the 3D reflection seismic method into the near-surface area of geophysical applications, especially in response to the emergence of the need to comprehensively characterize and monitor near-surface carbon dioxide sequestration in shallow saline aquifers around the world, justifies the emphasis on cost-effective and robust quality control and assurance （QC/QA） workflow of 3D seismic data preprocessing that is suitable for near-surface applications. The main purpose of our seismic data preprocessing QC is to enable the use of appropriate header information, data that are free of noise-dominated traces, and/or flawed vertical stacking in subsequent processing steps. In this article, I provide an account of utilizing survey design specifications, noise properties, first breaks, and normal moveout for rapid and thorough graphical QC/QA diagnostics, which are easy to apply and efficient in the diagnosis of inconsistencies. A correlated vibroseis time-lapse 3D-seismic data set from a CO2-flood monitoring survey is used for demonstrating QC diagnostics. An important by-product of the QC workflow is establishing the number of layers for a refraction statics model in a data-driven graphical manner that capitalizes on the spatial coverage of the 3D seismic data.
文摘迹线是节理与岩体临空面相交形成的空间曲线,其几何形态直接反映岩体的结构特征。因此,快速准确地提取迹线信息具有重要的理论意义和工程价值。目前,基于空间点云数据的迹线提取多基于曲率开展,较少考虑点云的色彩信息,加之空间点云数量庞大,精度与效率均不理想。鉴于此,提出了一种新的基于降维投影的迹线提取方法(a new trace line extraction method based on dimensionality reduction projection,简称NTDR)。该方法将三维点云保形投影到二维平面,基于二维点云颜色信息进行高效边缘检测,结合三维点云的曲率及距离等几何特征进行聚类连线,实现了节理迹线的自动提取。研究表明:(1)相比于人工提取方法,NTDR处理大规模点云数据的时间节省了约91.07%,大幅提升了提取效率;(2)NTDR提取的迹线与人工提取相比,重合率达90.42%,且局部细节更多,在效果、精度上具有优越性;(3)NTDR在20%的噪点干扰下能保持80%以上的识别正确率,受噪点影响小;(4)相比于同类自动化迹线提取方法,NTDR在提取效果上有优势,更符合岩体实际的迹线分布情况。该方法可提升地质灾害预测效率,为隧道支护设计及工程安全评估提供数据支撑。
基金National Natural Science Foundation of China(Nos.40774078,40774077)the Chinese Academy of Sciences(No.KZCX3-SW-144)
文摘The effect of the azimuthal angle φ of the wave vector k on the propagation characteristics of the superluminous L-O mode waves （together with a case of the R-X mode） during different geomagnetic activities using a three-dimensional （3D） ray-tracing method is investigated. This work is primarily an extension of our previous two-dimensional study in which the wave azimuthal angle was not considered. We present numerical simulations for this mode which is generated in the source cavity along a 70° night geomagnetic field line at the specific altitude of 1.5RE （where RE is the Earth＇s radius）. It is found that, as in the two-dimensional case, the trajectory of L-O mode starting in the source meridian plane （or the wave azimuthal angle φ = 180°） can reach the lowest latitude; whereas it basically stays at relatively higher latitudes starting off the source meridian plane （or φ=180°）. The results reveal that under appropriate conditions, the superluminous L-O mode waves may exist in the radiation belts of the Earth, but this remains to be supplemented by observational data.
