The Pre-Stack Depth Migration （PSDM） method based on wavefield continuation is the most reliable method for imaging complex structure in the subsurface, although there are large computational costs and poorly adapti...The Pre-Stack Depth Migration （PSDM） method based on wavefield continuation is the most reliable method for imaging complex structure in the subsurface, although there are large computational costs and poorly adaptive geometry. Plane wave shot migration is another method to perform exact wave equation prestack imaging with high computational efficiency and without the migration aperture problem. Moreover, wavefield energy can be compensated at the target zone by controlled illumination. In this paper, plane wave shot PSDM was implemented by the control of the plane down-going wavefield and selection of number and range of the raypaths in order to optimize the imaging effect. In addition, controlled illumination techniques are applied to enhance the imaging precision of interesting areas at different depths. Numerical calculation indicates that plane wave shot imaging is a rapid and efficient method with less computational cost and easy parallel computation compared to the single-square-root operator imaging for common shot gathers and double- square-root operator imaging for common midpoint gathers.展开更多
Wave front healing is a common natural phenomenon.To further investigate wave front healing,we simulated wave propagation in a spherical anomaly surrounded by homogeneous media using a high-order finite difference sol...Wave front healing is a common natural phenomenon.To further investigate wave front healing,we simulated wave propagation in a spherical anomaly surrounded by homogeneous media using a high-order finite difference solution of the acoustic equation.Furthermore,we analyzed the characteristics of the wave propagation in the anomaly,and found that they are related to the dominant frequency of the seismic wave and the dimensions of the anomaly.Through quantitative comparison of the wave front energy of the diffracted wave and transmitted wave,we summarized the influences of the wave front healing on seismic tomography.We conclude that,under the strong scattering condition,only positive anomalies can be inverted by ray-based tomography,only large anomalies can be inverted by finite-frequency tomography,and small negative anomalies cannot be inverted by any first-arrival traveltime tomographic methods.These conclusions are verified by tomographic experiments based on different theoretical models.Finally,we propose that more information besides the first-arrival traveltime should be used to invert the high wave number components of the media.Besides the above acquisitions of wave front healing on seismic tomography,we explain the banana-doughnut phenomena,and offer a new insight into the wave scattering,which should be important for better understanding the wave propagation and seismic inversion.展开更多
基金This project is sporspored by Fund item:the National Development and Innovation Committee Program (2005) 2372the National High-tech R&D Program (863 Program) 2006AA06Z241 of ChinaYouth Innovation Fund of CNPC (Program:Prestack Imaging Integral Study for Complex near Surface)
文摘The Pre-Stack Depth Migration （PSDM） method based on wavefield continuation is the most reliable method for imaging complex structure in the subsurface, although there are large computational costs and poorly adaptive geometry. Plane wave shot migration is another method to perform exact wave equation prestack imaging with high computational efficiency and without the migration aperture problem. Moreover, wavefield energy can be compensated at the target zone by controlled illumination. In this paper, plane wave shot PSDM was implemented by the control of the plane down-going wavefield and selection of number and range of the raypaths in order to optimize the imaging effect. In addition, controlled illumination techniques are applied to enhance the imaging precision of interesting areas at different depths. Numerical calculation indicates that plane wave shot imaging is a rapid and efficient method with less computational cost and easy parallel computation compared to the single-square-root operator imaging for common shot gathers and double- square-root operator imaging for common midpoint gathers.
基金supported by National Natural Science Foundation of China(Grant No. 40804023)National Basic Research Program of China (Grant No. 2006CB202402)+1 种基金Hi-tech R&D Program of China (Grant No.2008AA093001)Project of State Key Laboratory of Marine Geology of China (Grant No. MG200909)
文摘Wave front healing is a common natural phenomenon.To further investigate wave front healing,we simulated wave propagation in a spherical anomaly surrounded by homogeneous media using a high-order finite difference solution of the acoustic equation.Furthermore,we analyzed the characteristics of the wave propagation in the anomaly,and found that they are related to the dominant frequency of the seismic wave and the dimensions of the anomaly.Through quantitative comparison of the wave front energy of the diffracted wave and transmitted wave,we summarized the influences of the wave front healing on seismic tomography.We conclude that,under the strong scattering condition,only positive anomalies can be inverted by ray-based tomography,only large anomalies can be inverted by finite-frequency tomography,and small negative anomalies cannot be inverted by any first-arrival traveltime tomographic methods.These conclusions are verified by tomographic experiments based on different theoretical models.Finally,we propose that more information besides the first-arrival traveltime should be used to invert the high wave number components of the media.Besides the above acquisitions of wave front healing on seismic tomography,we explain the banana-doughnut phenomena,and offer a new insight into the wave scattering,which should be important for better understanding the wave propagation and seismic inversion.
