Gaussian beam migration （GBM） is an effec- tive and robust depth seismic imaging method, which overcomes the disadvantage of Kirchhoff migration in imaging multiple arrivals and has no steep-dip limitation of one-wa...Gaussian beam migration （GBM） is an effec- tive and robust depth seismic imaging method, which overcomes the disadvantage of Kirchhoff migration in imaging multiple arrivals and has no steep-dip limitation of one-way wave equation migration. However, its imaging quality depends on the initial beam parameters, which can make the beam width increase and wave-front spread with the propagation of the central ray, resulting in poor migration accuracy at depth, especially for exploration areas with complex geological structures. To address this problem, we present an adaptive focused beam method for shot-domain prestack depth migration. Using the infor- mation of the input smooth velocity field, we first derive an adaptive focused parameter, which makes a seismic beam focused along the whole central ray to enhance the wave- field construction accuracy in both the shallow and deep regions. Then we introduce this parameter into the GBM, which not only improves imaging quality of deep reflectors but also makes the shallow small-scale geological struc- tures well-defined. As well, using the amplitude-preserved extrapolation operator and deconvolution imaging condi- tion, the concept of amplitude-preserved imaging has been included in our method. Typical numerical examples and the field data processing results demonstrate the validity and adaptability of our method.展开更多
Focusing in solids by surface transducer arrays ( STA ) and the acoustic field distribution on the focal axis are studied in this paper. The relation between the source element width and the field strength at differen...Focusing in solids by surface transducer arrays ( STA ) and the acoustic field distribution on the focal axis are studied in this paper. The relation between the source element width and the field strength at different order focuses is also discussed. Numerical calculation is used to get the focal field distribution as the element width is changed. Some practical problems such as the minimum distinguishable frequency, the transversal and longitudinal resolution are investigated when this kind of focusing is used for NDT and acoustic imaging. Some explorative experiments have been done to demonstrate the theory.展开更多
文摘Gaussian beam migration （GBM） is an effec- tive and robust depth seismic imaging method, which overcomes the disadvantage of Kirchhoff migration in imaging multiple arrivals and has no steep-dip limitation of one-way wave equation migration. However, its imaging quality depends on the initial beam parameters, which can make the beam width increase and wave-front spread with the propagation of the central ray, resulting in poor migration accuracy at depth, especially for exploration areas with complex geological structures. To address this problem, we present an adaptive focused beam method for shot-domain prestack depth migration. Using the infor- mation of the input smooth velocity field, we first derive an adaptive focused parameter, which makes a seismic beam focused along the whole central ray to enhance the wave- field construction accuracy in both the shallow and deep regions. Then we introduce this parameter into the GBM, which not only improves imaging quality of deep reflectors but also makes the shallow small-scale geological struc- tures well-defined. As well, using the amplitude-preserved extrapolation operator and deconvolution imaging condi- tion, the concept of amplitude-preserved imaging has been included in our method. Typical numerical examples and the field data processing results demonstrate the validity and adaptability of our method.
文摘Focusing in solids by surface transducer arrays ( STA ) and the acoustic field distribution on the focal axis are studied in this paper. The relation between the source element width and the field strength at different order focuses is also discussed. Numerical calculation is used to get the focal field distribution as the element width is changed. Some practical problems such as the minimum distinguishable frequency, the transversal and longitudinal resolution are investigated when this kind of focusing is used for NDT and acoustic imaging. Some explorative experiments have been done to demonstrate the theory.
