2D acoustic-elastic coupled waveform inversion in the Laplace domain

ABSTRACT Although waveform inversion has been intensively studied in an effort to properly delineate the Earth's structures since the early 1980s, most of the time‐ and frequency‐domain waveform inversion algorithms still have critical limitations in their applications to field data. This may b...

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Bibliographic Details
Published in:Geophysical Prospecting Vol. 58; no. 6; pp. 997 - 1010
Main Authors: Bae, Ho Seuk, Shin, Changsoo, Cha, Young Ho, Choi, Yunseok, Min, Dong-Joo
Format: Journal Article
Language:English
Published: Oxford, UK Blackwell Publishing Ltd 01.11.2010
Blackwell
Subjects:
Acoustic-elastic coupled media
Acoustics
Algorithms
Applied geophysics
Earth
Earth sciences
Earth, ocean, space
Exact sciences and technology
Finite-element method
Geophysics
Internal geophysics
Inversions
Laplace domain
Long-wavelength
Mathematical models
Prospecting
Two dimensional
Waveform inversion
Waveforms
wavelength
algorithms
models
inverse problem
interfaces
elastic media
exploration
density
S-waves
pressure
velocity
finite element analysis
low frequency
frequency
Earth
depth
propagation
noise
waveforms
direction
ISSN:0016-8025, 1365-2478
Online Access:Get full text
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Summary:ABSTRACT Although waveform inversion has been intensively studied in an effort to properly delineate the Earth's structures since the early 1980s, most of the time‐ and frequency‐domain waveform inversion algorithms still have critical limitations in their applications to field data. This may be attributed to the highly non‐linear objective function and the unreliable low‐frequency components. To overcome the weaknesses of conventional waveform inversion algorithms, the acoustic Laplace‐domain waveform inversion has been proposed. The Laplace‐domain waveform inversion has been known to provide a long‐wavelength velocity model even for field data, which may be because it employs the zero‐frequency component of the damped wavefield and a well‐behaved logarithmic objective function. However, its applications have been confined to 2D acoustic media. We extend the Laplace‐domain waveform inversion algorithm to a 2D acoustic‐elastic coupled medium, which is encountered in marine exploration environments. In 2D acoustic‐elastic coupled media, the Laplace‐domain pressures behave differently from those of 2D acoustic media, although the overall features are similar to each other. The main differences are that the pressure wavefields for acoustic‐elastic coupled media show negative values even for simple geological structures unlike in acoustic media, when the Laplace damping constant is small and the water depth is shallow. The negative values may result from more complicated wave propagation in elastic media and at fluid‐solid interfaces. Our Laplace‐domain waveform inversion algorithm is also based on the finite‐element method and logarithmic wavefields. To compute gradient direction, we apply the back‐propagation technique. Under the assumption that density is fixed, P‐ and S‐wave velocity models are inverted from the pressure data. We applied our inversion algorithm to the SEG/EAGE salt model and the numerical results showed that the Laplace‐domain waveform inversion successfully recovers the long‐wavelength structures of the P‐ and S‐wave velocity models from the noise‐free data. The models inverted by the Laplace‐domain waveform inversion were able to be successfully used as initial models in the subsequent frequency‐domain waveform inversion, which is performed to describe the short‐wavelength structures of the true models.
Bibliography:ark:/67375/WNG-0XGK4HX8-S
ArticleID:GPR879
istex:F40FD9271E2F7007987B689893D69E0716A904DF
ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 23
ISSN:0016-8025
1365-2478
DOI:10.1111/j.1365-2478.2010.00879.x