This paper discusses Born/Rytov approximation tomographic velocity inversion methods constrained by the Fresnel zone. Calculations of the sensitivity kernel function and traveltime residuals are critical in tomographi...This paper discusses Born/Rytov approximation tomographic velocity inversion methods constrained by the Fresnel zone. Calculations of the sensitivity kernel function and traveltime residuals are critical in tomographic velocity inversion. Based on the Bom/Rytov approximation of the frequency-domain wave equation, we derive the traveltime sensitivity kemels of the wave equation on the band-limited wave field and simultaneously obtain the traveltime residuals based on the Rytov approximation. In contrast to single-ray tomography, the modified velocity inversion method improves the inversion stability. Tests of the near- surface velocity model and field data prove that the proposed method has higher accuracy and Computational efficiency than ray theory tomography and full waveform inversion methods.展开更多
In the field of geophysics,although the first-order Rytov approximation is widely used,the higher-order approximation is seldom discussed.From both theo-retical analysis and numerical tests,the accumulated phase error...In the field of geophysics,although the first-order Rytov approximation is widely used,the higher-order approximation is seldom discussed.From both theo-retical analysis and numerical tests,the accumulated phase error introduced in the first-order Rytov approximation cannot be neglected in the presence of strong velocity perturbation.In this paper,we are focused on improving the phase accuracy of forward scattered wavefield,especially for the large-scale and strong velocity pertur-bation case.We develop an equivalent source method which can update the imaginary part of the complex phase iteratively,and the higher-order scattered wavefield can be approximated by multiplying the incident wavefield by the exponent of the imaginary part of the complex phase.Although the convergence of the proposed method has not been proved mathematically,numerical examples demonstrate that our method can produce an improved accuracy for traveltime(phase)prediction,even for strong perturbation media.However,due to the neglect of the real part of the complex phase,the amplitude change of the scattered wavefield cannot be recovered.Furthermore,in the presence of multi-arrivals phenomenon,the equivalent scattering source should be handled carefully due to the multi-directions of the wavefield.Further investigations should be done to improve the applicability of the proposed method.展开更多
基金sponsored by the National Natural Science Foundation of China(No.41204086)the Self-governed Innovative Project of China University of Petroleum(No.13CX02041A)+2 种基金the Doctoral Fund of National Ministry of Education(No.20110133120001)the National 863 Project(2011AA060301)the Major National Science and Technology Program(No.2011ZX05006-002)
文摘This paper discusses Born/Rytov approximation tomographic velocity inversion methods constrained by the Fresnel zone. Calculations of the sensitivity kernel function and traveltime residuals are critical in tomographic velocity inversion. Based on the Bom/Rytov approximation of the frequency-domain wave equation, we derive the traveltime sensitivity kemels of the wave equation on the band-limited wave field and simultaneously obtain the traveltime residuals based on the Rytov approximation. In contrast to single-ray tomography, the modified velocity inversion method improves the inversion stability. Tests of the near- surface velocity model and field data prove that the proposed method has higher accuracy and Computational efficiency than ray theory tomography and full waveform inversion methods.
基金supported by National Natural Science Foundation of China(41604091,41704111,41774126)the great and special project(2016ZX05024-001,2016ZX05006-002).
文摘In the field of geophysics,although the first-order Rytov approximation is widely used,the higher-order approximation is seldom discussed.From both theo-retical analysis and numerical tests,the accumulated phase error introduced in the first-order Rytov approximation cannot be neglected in the presence of strong velocity perturbation.In this paper,we are focused on improving the phase accuracy of forward scattered wavefield,especially for the large-scale and strong velocity pertur-bation case.We develop an equivalent source method which can update the imaginary part of the complex phase iteratively,and the higher-order scattered wavefield can be approximated by multiplying the incident wavefield by the exponent of the imaginary part of the complex phase.Although the convergence of the proposed method has not been proved mathematically,numerical examples demonstrate that our method can produce an improved accuracy for traveltime(phase)prediction,even for strong perturbation media.However,due to the neglect of the real part of the complex phase,the amplitude change of the scattered wavefield cannot be recovered.Furthermore,in the presence of multi-arrivals phenomenon,the equivalent scattering source should be handled carefully due to the multi-directions of the wavefield.Further investigations should be done to improve the applicability of the proposed method.
