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Results
Improvements in Time Domain FWI and its Applications
Yoon, Kwangjin (TGS) | Suh, Sang (TGS) | Cai, James (TGS) | Wang, Bin (TGS)
Summary In this abstract, we describe how to improve time domain full waveform inversion using source wavelet convolution, windowed back propagation and source side illumination. Instead of estimating the source wavelet from field data, a user defined source wavelet can be convolved to field data. This convolution makes waveform matching between modeled and field data easier. Increasing time window applied to residual enables top down velocity update and reduces the possibility of being stuck at a local minimum. The balance of gradient value can be improved by the illumination compensation using the square of source side wavefield. Well balanced gradient helps FWI restore the absolute value of velocity. We apply this method to estimate migration velocities using 2D and 3D synthetic and real data examples.
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling > Seismic Inversion (0.68)
Compensating Visco-Acoustic Effects in Anisotropic Resverse-Time Migration
Suh, Sang (TGS) | Yoon, Kwangjin (TGS) | Cai, James (TGS) | Wang, Bin (TGS)
SUMMARY Anelastic properties of the earth cause frequency dependent energy attenuation and phase distortion in seismic wave propagation. It is preferred that these unwanted effects be corrected in a prestack depth migration. Zhang et al (2010) introduced a visco-acoustic wave equation in the time domain for isotropic media. This paper extends the visco-acoustic wave equation for anisotropic case, and develops visco-acoustic reverse time migration algorithm for VTI medium. To validate the proposed wave equation, wave propagation is simulated on a homogeneous viscous VTI medium using a finite difference method. The wavefield snapshot shows predicted frequency dependent attenuation and dispersion. Synthetic and field data examples are also given.