HR: 11:30h
AN: S32A-05    [Abstracts]
TI: Two-dimensional Full Waveform Inversion
AU: * Li, K
EM: apg8810@eq.ccu.edu.tw
AF: Kun-Sung Li, Natl. Chung Cheng Univ., 160, San-Hsing, Min-Hsiung, Chia-Yi, Taiwan, Chia-Yi, 621 Taiwan
AU: Chen, H
EM: hwchen@cc.ncu.edu.tw
AF: How-Wei Chen, Natl. Central Univ., 300, Jhongda, Jhongli, Taoyuan, Taiwan, Taoyuan, 320 Taiwan
AB: A two-dimensional full wavefield inversion for direct imaging of compressional wave and out-of-plane standing wave (SH) velocity distribution is developed, tested and implemented. The inversion is base on the finite difference solution of the full two-dimension scalar wave equation in the time-distance domain and operates on wide-aperture, common-shot data. The computational kernel fully utilizes the reverse-time image reconstruction principles. No travel-time picking and phase identification are required for full waveform inversion. For each shot records, gradients of misfit function (Frechét derivative) are dynamically determined by cross-correlation of the recorded forward propagating wavefield and backward propagating residual wavefield at each time step. Convergence to local minima can be avoided by gradually increasing the wavenumber bandwidth in the estimated velocity distribution and to increase the inversion resolution as iterations proceed. Synthetic examples show that the effects of the multiples, scattering, artificial boundary reflection waves, or noise do not contaminate the final results and convergences successfully to the correct solution. Using full two-way waveform approach for seismic imaging simplifies un-necessary skeleton seismic processing procedures. Furthermore, the resolution of inversion result is limited by the bandwidth of field recordings, source wavelet and dominant frequency. Convergence rate and stability of our in-house development of inversion algorithm is highly depends on step length and the complexity of subsurface structure associate with the steepest decent direction. For land data, near-surface effects including topography, lateral velocity variation, source and receiver static corrections are automatically included. For marine seismic data, multiples generated by water layer can be effectively suppressed through wavefield based seismic processing approach.
DE: 0540 Image processing
DE: 3260 Inverse theory
DE: 3285 Wave propagation (0689, 2487, 4275, 4455, 6934)
DE: 7270 Tomography (6982, 8180)
DE: 7290 Computational seismology
SC: Seismology [S]
MN: Fall Meeting 2005