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Yoon B.,Shins Geophysics | Ha W.,Shins Geophysics | Son W.,Shins Geophysics | Shin C.,Shins Geophysics | Calandra H.,Total S.A.
SEG Technical Program Expanded Abstracts | Year: 2011

3D Laplace-domain waveform inversion can recover a large velocity model for successive waveform inversion in the frequency domain. However, the grid interval in 3D Laplace-domain modeling and inversion cannot be sufficiently small because of the heavy computational cost. Therefore, we cannot assess whether or not the modeled wavefield is reliable if our model has an abruptly undulated sea bottom surface. The irregular finite element method can provide a solution; however, it increases the number of bands of the impedance matrix. Instead, we applied the Gaussian quadrature integration method in order to reflect two properties on one element at the irregular sea bottom. In order to verify this modeling algorithm, we compared our modeled wavefield with the analytic solutions for an unbounded homogeneous model, an unbounded two-layer model and an obliquely-inclined two-layer model. The results of the verification tests show that our modeling algorithm better describes a wavefield with an irregular sea bottom in the 3D Laplace domain than the conventional modeling algorithm. © 2011 Society of Exploration Geophysicists. Source

Ha W.,Shins Geophysics | Yoo J.,Shins Geophysics | Shin C.,Shins Geophysics
SEG Technical Program Expanded Abstracts | Year: 2011

In this paper, we suggest a new method for velocity estimation in the Laplace domain. We applied gain functions to observed data and used the results to calculate gradients. We started with a homogeneous velocity and used the analytic solution of the acoustic wave equation. This method is fast and efficient. On the other hand, only one velocity update is possible, as we used the analytic solution. A numerical example of field data shows that this method can be used to recover large-scale velocity structures. © 2011 Society of Exploration Geophysicists. Source

Kang S.,Shins Geophysics | Bae H.S.,Shins Geophysics | Shin C.,Shins Geophysics
SEG Technical Program Expanded Abstracts | Year: 2011

Most full waveform inversion algorithms have been developed assuming that the governing equation of the wave-propagation phenomenon is the acoustic wave equation. However, the majority of geophysical targets are generally situated in elastic media. For this reason, waveform inversion using an acoustic wave equation has its limitations with regard to building submarine geophysical features. Accordingly, we have proposed a full waveform inversion algorithm for coupled acoustic-elastic media with irregular submarine topography that is comparable to submarine geology systems. We developed a hybrid (Laplace-Fourier domain) waveform inversion technique that uses both frequency- and Laplace-domain wavefields properly. The frequency-domain wavefield has a short-wavelength component which can describe detailed velocity models. On the other hand, the employed Laplace coefficients have a long-wavelength component which can describe macro velocity structures. In addition, we proposed a strategy for selecting frequency bands, comprising selected real frequencies and Laplace coefficients. From numerical tests, using a synthetic model (2D AA profile of the SEG/EAGE salt model) and a field dataset (North-East Atlantic), our new hybrid waveform inversion strategy provided much higher resolution images than conventional hybrid inversion schemes. © 2011 Society of Exploration Geophysicists. Source

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