Wookeen Chung

Non-uniqueness of waveform inversions in the Laplace domain

The non-uniqueness of the solution is one of the major obstacles for a successful full waveform inversion. This paper shows that there are at least two solutions for waveform inversions in the Laplace domain: the true velocity model; the long-wavelength background velocity model. The Laplace domain inversion can recover the true velocity model if provided with an accurate initial model, but it will instead result in a smooth long-wavelength velocity model if the initial model is inaccurate and smooth. In this case, the inverted long-wavelength velocity model can still be used for either migration or as an initial velocity model for frequency domain waveform inversion.

A proposal of seismic oceanography for temperature model inversion of the East Sea, Korea

Much attention has recently been paid to the East Sea because of the great influence it exerts on weather in the Korean peninsula as well as its peculiar oceanographic features. A large number of oceanographic observations have been made to probe the physical properties of the waters at the East Sea. However, until now, measuring the physical properties of a broad oceanic area simultaneously was impractical. To address this problem, this study presents a methodology to measure the physical properties of seawater by introducing seismic oceanography (SO) into marine seismic surveys. SO has been attracting attention as a new technology capable of concurrent analysis of a broad oceanic area; however, hardly any research of this type has been conducted in Korea to date. The technique proposed in this study involves derivation of a seawater temperature model based on the 1D seismic waveform inversion and Leroy equations using seismic data and non-stationary ARGO data. The proposed technique was validated through numerical model experiments using the seawater temperature information obtained at the East Sea in 2013, through which much insight into the ocean currents and seawater characteristics of the East Sea could be gained.

Kirchhoff prestack migration using the suppressed wave equation estimation of traveltime (SWEET) algorithm in VTI media

This paper examines anisotropic prestack Kirchhoff migration. We used pseudo-acoustic wave equations in the complex frequency domain to describe the wave propagation in a vertical transversely isotropic (VTI) medium. Both amplitudes and traveltimes were calculated efficiently using the suppressed wave equation estimation of traveltime (SWEET) algorithm. The accuracy of the traveltimes obtained with the SWEET algorithm was verified by comparing the traveltime contours simulated with the anisotropic elastic wave equation using a staggered-grid method. Finally, we tested our migration algorithm using the two-dimensional HESS VTI model. We correctly imaged the shape of both the salt and background layer structures. We also reduced the numerical artefacts compared to the isotropic technique. This paper examines anisotropic prestack Kirchhoff migration using the pseudo-acoustic wave equation in a vertical transversely isotropic (VTI) medium. Both amplitudes and traveltimes were calculated efficiently for migration using the suppressed wave equation estimation of traveltime (SWEET) algorithm.