3D P‐wave traveltime computation in transversely isotropic media using layer‐by‐layer wavefront marching |
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| Authors: | Jiangtao Hu Junxing Cao Huazhong Wang Xingjian Wang Renfei Tian |
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| Affiliation: | 1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, Sichuan, P.R. China;2. College of Geophysics, Chengdu University of Technology, Chengdu, Sichuan, P.R. China;3. WPI, School of Ocean and Earth Science, Tongji University, Shanghai, P.R. China |
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| Abstract: | Subsurface rocks (e.g. shale) may induce seismic anisotropy, such as transverse isotropy. Traveltime computation is an essential component of depth imaging and tomography in transversely isotropic media. It is natural to compute the traveltime using the wavefront marching method. However, tracking the 3D wavefront is expensive, especially in anisotropic media. Besides, the wavefront marching method usually computes the traveltime using the eikonal equation. However, the anisotropic eikonal equation is highly non‐linear and it is challenging to solve. To address these issues, we present a layer‐by‐layer wavefront marching method to compute the P‐wave traveltime in 3D transversely isotropic media. To simplify the wavefront tracking, it uses the traveltime of the previous depth as the boundary condition to compute that of the next depth based on the wavefront marching. A strategy of traveltime computation is designed to guarantee the causality of wave propagation. To avoid solving the non‐linear eikonal equation, it updates traveltime along the expanding wavefront by Fermat's principle. To compute the traveltime using Fermat's principle, an approximate group velocity with high accuracy in transversely isotropic media is adopted to describe the ray propagation. Numerical examples on 3D vertical transverse isotropy and tilted transverse isotropy models show that the proposed method computes the traveltime with high accuracy. It can find applications in modelling and depth migration. |
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| Keywords: | 3D traveltime computation Wavefront marching TI media Fermat's principle Explicit group velocity |
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