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Changsoo Shin - One of the best experts on this subject based on the ideXlab platform.
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A comparison of the preconditioning effects of different parameterization methods for monoparameter full waveform inversions in the Laplace Domain
Journal of Applied Geophysics, 2020Co-Authors: Byeonggyeong Park, Changsoo ShinAbstract:Abstract We examined the preconditioning effects of model parameterizations using the bulk modulus, logarithmic velocity, slowness, and sloth instead of the P-wave velocity, which is commonly used, for monoparameter acoustic full waveform inversions in the Laplace Domain. Introducing the bulk modulus, logarithmic velocity, slowness, and sloth modifies the gradient direction of the velocity parameterization according to the chain rule, and these modifications function as preconditioners for the gradient direction and affect the inversion results. We compared five different parameterization methods for monoparameter Laplace-Domain full waveform inversions. We also compared the results obtained using an initial velocity model that varies linearly with those obtained using a constant initial velocity model. The logarithmic velocity, slowness, and sloth parameterization methods provided better inversion results than those from the bulk modulus and velocity parameterization in the numerical examples using the Pluto and SEG/EAGE salt models.
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interrelation between Laplace constants and the gradient distortion effect in Laplace Domain waveform inversion
Geophysics, 2017Co-Authors: Jungmin Kwon, Hyojoon Jin, Henri Calandra, Changsoo ShinAbstract:ABSTRACTLaplace-Domain waveform inversion (WI) is generally used to generate smooth initial velocity models for frequency- or time-Domain full-waveform inversion. However, in the inversion results of Laplace-Domain WI, anomalies such as salt domes are sometimes shifted. We evaluate the “gradient-distortion effect” that causes undesirable changes in parameter updates and found that this is caused by the relationship between the partial derivatives of Laplace wavefields with respect to two different parameters. By analyzing the gradient of the Laplace-Domain misfit function, we found that the gradient distortion effect increases as the Laplace constants used in the Laplace-Domain WI decrease. The velocity model inverted in the Laplace Domain is generally blurred from shallower parameters to deeper parameters because the partial derivatives of the Laplace wavefields with respect to shallower parameters tend to be larger than those of deeper parameters. We found two solutions for suppressing the gradient dist...
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Laplace Domain waveform modeling and inversion for the 3d acoustic elastic coupled media
Journal of Applied Geophysics, 2016Co-Authors: Jungkyun Shin, Changsoo Shin, Henri CalandraAbstract:Abstract Laplace-Domain waveform inversion reconstructs long-wavelength subsurface models by using the zero-frequency component of damped seismic signals. Despite the computational advantages of Laplace-Domain waveform inversion over conventional frequency-Domain waveform inversion, an acoustic assumption and an iterative matrix solver have been used to invert 3D marine datasets to mitigate the intensive computing cost. In this study, we develop a Laplace-Domain waveform modeling and inversion algorithm for 3D acoustic–elastic coupled media by using a parallel sparse direct solver library (MUltifrontal Massively Parallel Solver, MUMPS). We precisely simulate a real marine environment by coupling the 3D acoustic and elastic wave equations with the proper boundary condition at the fluid-solid interface. In addition, we can extract the elastic properties of the Earth below the sea bottom from the recorded acoustic pressure datasets. As a matrix solver, the parallel sparse direct solver is used to factorize the non-symmetric impedance matrix in a distributed memory architecture and rapidly solve the wave field for a number of shots by using the lower and upper matrix factors. Using both synthetic datasets and real datasets obtained by a 3D wide azimuth survey, the long-wavelength component of the P-wave and S-wave velocity models is reconstructed and the proposed modeling and inversion algorithm are verified. A cluster of 80 CPU cores is used for this study.
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Laplace-Domain waveform modeling and inversion for the 3D acoustic–elastic coupled media
Journal of Applied Geophysics, 2016Co-Authors: Jungkyun Shin, Changsoo Shin, Henri CalandraAbstract:Abstract Laplace-Domain waveform inversion reconstructs long-wavelength subsurface models by using the zero-frequency component of damped seismic signals. Despite the computational advantages of Laplace-Domain waveform inversion over conventional frequency-Domain waveform inversion, an acoustic assumption and an iterative matrix solver have been used to invert 3D marine datasets to mitigate the intensive computing cost. In this study, we develop a Laplace-Domain waveform modeling and inversion algorithm for 3D acoustic–elastic coupled media by using a parallel sparse direct solver library (MUltifrontal Massively Parallel Solver, MUMPS). We precisely simulate a real marine environment by coupling the 3D acoustic and elastic wave equations with the proper boundary condition at the fluid-solid interface. In addition, we can extract the elastic properties of the Earth below the sea bottom from the recorded acoustic pressure datasets. As a matrix solver, the parallel sparse direct solver is used to factorize the non-symmetric impedance matrix in a distributed memory architecture and rapidly solve the wave field for a number of shots by using the lower and upper matrix factors. Using both synthetic datasets and real datasets obtained by a 3D wide azimuth survey, the long-wavelength component of the P-wave and S-wave velocity models is reconstructed and the proposed modeling and inversion algorithm are verified. A cluster of 80 CPU cores is used for this study.
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Laplace-Domain Waveform Inversion for the 3D Acoustic-elastic Coupled Media
77th EAGE Conference and Exhibition 2015, 2015Co-Authors: Jungkyun Shin, Y Park, H. Jin, Changsoo ShinAbstract:In the marine streamer survey, the sources and receivers are located in the homogeneous acoustic media; however, the media below the sea bottom, which is the target area, has highly heterogeneous 3D elastic properties. Thus, the hydrophone pressure data contain various elastic effects, such as shear wave effects, mode converted waves and amplitude offset variation, and these effects impact the Laplace-transformed wavefield. Therefore, it is not possible to perfectly reduce the misfit between modelled and observed data using only acoustic wave equations. In this study, we developed a Laplace-Domain waveform inversion algorithm for 3D acoustic-elastic coupled media. We can precisely simulate the environment of a conventional streamer marine survey by coupling the 3D acoustic and elastic wave equations using a proper boundary condition at the solid-fluid interface. Also, for the matrix solver, we suggest using the parallel sparse direct solver library, which was developed by the MUltifrontal Massively Parallel Solver (MUMPS) team. Because this is a direct matrix solver, we do net lose the main advantage of implicit modeling (e.g., frequency or Laplace Domain modeling) over the explicit time-Domain modelling when we solve the wave field for a number of shots.
Wookeen Chung - One of the best experts on this subject based on the ideXlab platform.
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2d Laplace Domain waveform inversion of field data using a power objective function
Pure and Applied Geophysics, 2013Co-Authors: Eun-jin Park, Changsoo Shin, Wookeen Chung, Dong-joo MinAbstract:The wavefield in the Laplace Domain has a very small amplitude except only near the source point. In order to deal with this characteristic, the logarithmic objective function has been used in many Laplace Domain inversion studies. The Laplace-Domain waveform inversion using the logarithmic objective function has fewer local minima than the time- or frequency Domain inversion. Recently, the power objective function was suggested as an alternative to the logarithmic objective function in the Laplace Domain. Since amplitudes of wavefields are very small generally, a power <1 amplifies the wavefields especially at large offset. Therefore, the power objective function can enhance the Laplace-Domain inversion results. In previous studies about synthetic datasets, it is confirmed that the inversion using a power objective function shows a similar result when compared with the inversion using a logarithmic objective function. In this paper, we apply an inversion algorithm using a power objective function to field datasets. We perform the waveform inversion using the power objective function and compare the result obtained by the logarithmic objective function. The Gulf of Mexico dataset is used for the comparison. When we use a power objective function in the inversion algorithm, it is important to choose the appropriate exponent. By testing the various exponents, we can select the range of the exponent from 5 × 10−3 to 5 × 10−8 in the Gulf of Mexico dataset. The results obtained from the power objective function with appropriate exponent are very similar to the results of the logarithmic objective function. Even though we do not get better results than the conventional method, we can confirm the possibility of applying the power objective function for field data. In addition, the power objective function shows good results in spite of little difference in the amplitude of the wavefield. Based on these results, we can expect that the power objective function will produce good results from the data with a small amplitude difference. Also, it can partially be utilized at the sections where the amplitude difference is very small.
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2D Laplace-Domain Waveform Inversion of Field Data Using a Power Objective Function
Pure and Applied Geophysics, 2013Co-Authors: Eun-jin Park, Changsoo Shin, Wookeen Chung, Dong-joo MinAbstract:The wavefield in the Laplace Domain has a very small amplitude except only near the source point. In order to deal with this characteristic, the logarithmic objective function has been used in many Laplace Domain inversion studies. The Laplace-Domain waveform inversion using the logarithmic objective function has fewer local minima than the time- or frequency Domain inversion. Recently, the power objective function was suggested as an alternative to the logarithmic objective function in the Laplace Domain. Since amplitudes of wavefields are very small generally, a power
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2 d acoustic Laplace Domain waveform inversion of marine field data
Geophysical Journal International, 2012Co-Authors: Wookeen Chung, Eun-jin Park, Changsoo ShinAbstract:SUMMARY The Laplace-Domain full waveform inversion method can build a macroscale subsurface velocity model that can be used as an accurate initial model for a conventional full waveform inversion. The acoustic Laplace-Domain inversion produced is promising for marine field data examples. Although applying an acoustic inversion method to the field data generally requires several pre-processing steps, pre-processing for the Laplace-Domain inversion has not been explained in detail. We provide a detailed explanation of how to apply the Laplace-Domain waveform inversion to field data through numerical tests with Gulf of Mexico data sets. The pre-processing includes bandpass filtering, muting of the noise before the first arrival, and extraction of the water depth. We choose the range and the interval between the Laplace damping constants empirically by applying a threshold value to the damped time traces and the Laplace-Domain wavefields. The observed data are transformed to the Laplace Domain using the selected damping; this method yielded a long-wavelength inversion result. The damping constant and the maximum offset affect the penetration depth of the inversion result. The maximum recording time is important for a stable Laplace-transformation and affects the inversion result; however, the latter effect is not significant.
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Laplace-Domain waveform inversion versus refraction-traveltime tomography
Geophysical Journal International, 2012Co-Authors: Ho Seuk Bae, Changsoo Shin, Sukjoon Pyun, Kurt J. Marfurt, Wookeen ChungAbstract:SUMMARY Geophysicists and applied mathematicians have proposed a rich suite of long-wavelength velocity estimation algorithms to construct starting velocity models for subsequent pre-stack depth migration and inversion. Refraction-traveltime tomography derives subsurface velocity models from picked first-arrival traveltimes. In contrast, Laplace-Domain waveform inversion recovers long-wavelength velocity structure using the weighted amplitudes of first and later arrivals. There are several implementations of first-arrival traveltime inversion, with most based on ray tracing, and some based on the damped monochromatic wave equation, which accurately represent simple and finite-frequency first arrivals. Computationally, Laplace-Domain wavefield inversion is quite similar to refraction-traveltime tomography using damped monochromatic wavefield, but the objective functions used in inversion are radically different. As in classical ray trace-based traveltime inversion, the objective of refraction-traveltime tomography using damped monochromatic wavefield is to match the phase (traveltime) of the first arrival of each measured seismic trace. In contrast, the objective of Laplace-Domain wavefield inversion is to match the weighted amplitudes of both first and later arrivals to the weighted amplitudes of the measured seismic trace. Principles of refraction-traveltime tomography were used to generate velocity models of the earth one century ago. Laplace-Domain waveform inversion is a more recently introduced algorithm and has been less rigorously studied by the seismic research community, with many workers believing it be equivalent to finite-frequency first-arrival traveltime tomography. We show that Laplace-Domain waveform inversion is both theoretically and empirically different from finite-frequency first-arrival traveltime tomography. Specifically, we examine the Jacobian (sensitivity) kernels used in the two inversion schemes to quantify the different sensitivities (and hence the inversion results) of the two methods. Analysing both surface responses and sensitivity results, we show that the Laplace-Domain waveform inversion's sensitivity to later arrivals provides significantly improved resolution of deeper velocity structure than the first-arrival traveltime tomography. We demonstrate this capability using numerical inversion examples using a synthetic five-layer model and the synthetic BP benchmark model. Because of the similar algorithmic structure, Laplace-Domain waveform inversion fits neatly as a starting velocity model pre-processing component of a larger (multi) frequency-Domain wave equation inversion solution package.
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2‐D acoustic Laplace‐Domain waveform inversion of marine field data
Geophysical Journal International, 2012Co-Authors: Wookeen Chung, Eun-jin Park, Changsoo ShinAbstract:SUMMARY The Laplace-Domain full waveform inversion method can build a macroscale subsurface velocity model that can be used as an accurate initial model for a conventional full waveform inversion. The acoustic Laplace-Domain inversion produced is promising for marine field data examples. Although applying an acoustic inversion method to the field data generally requires several pre-processing steps, pre-processing for the Laplace-Domain inversion has not been explained in detail. We provide a detailed explanation of how to apply the Laplace-Domain waveform inversion to field data through numerical tests with Gulf of Mexico data sets. The pre-processing includes bandpass filtering, muting of the noise before the first arrival, and extraction of the water depth. We choose the range and the interval between the Laplace damping constants empirically by applying a threshold value to the damped time traces and the Laplace-Domain wavefields. The observed data are transformed to the Laplace Domain using the selected damping; this method yielded a long-wavelength inversion result. The damping constant and the maximum offset affect the penetration depth of the inversion result. The maximum recording time is important for a stable Laplace-transformation and affects the inversion result; however, the latter effect is not significant.
Sukjoon Pyun - One of the best experts on this subject based on the ideXlab platform.
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Laplace-Domain wave-equation modeling and full waveform inversion in 3D isotropic elastic media
Journal of Applied Geophysics, 2014Co-Authors: Woohyun Son, Changsoo Shin, Sukjoon Pyun, Han-joon KimAbstract:Abstract The 3D elastic problem has not been widely studied because of the computational burden. Over the past few years, 3D elastic full waveform inversion (FWI) techniques in the time and frequency Domains have been proposed by some researchers based on developments in computer science. However, these techniques still have the non-uniqueness and high nonlinearity problems. In this paper, we propose a 3D elastic FWI algorithm in the Laplace Domain that can mitigate these problems. To efficiently solve the impedance matrix, we adopt a first-order absorbing boundary condition that results in a symmetric system. A conjugate gradient (CG) solver can be used because the Laplace-Domain wave equation is naturally positive definite. We apply the Jacobi preconditioner to increase the convergence speed. We identify the permissible range of Laplace damping constants through dispersion analysis and accuracy tests. We perform the Laplace-Domain FWI based on a logarithmic objective function, and the inversion examples are designed for a land setting, which means that the source is vertically excited and multi-component data are considered. The inversion results indicate that the inversion that uses only the vertical component performs slightly better than the multi-component inversion. This unexpected result is obtained partly because we use a vertically polarized source. We analyze the residuals and Frechet derivatives for each component to examine the characteristics of the Laplace-Domain multi-component FWI. The results indicate that the residuals and Frechet derivatives for the horizontal component have a singularity problem. The numerical examples demonstrate that the singularity problem is related to the directivity of the displacement and to taking the logarithm of Laplace-Domain wave fields. To avoid this singularity problem, we use a simple method that excludes the data near the singular region. Although we can use either simultaneous or sequential strategies to invert the Laplace-Domain data, we apply a simultaneous inversion strategy in this paper. Nonetheless, the numerical examples demonstrate that our inversion algorithm yields reasonable long-wavelength velocity structures.
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Laplace-Domain waveform inversion versus refraction-traveltime tomography
Geophysical Journal International, 2012Co-Authors: Ho Seuk Bae, Changsoo Shin, Sukjoon Pyun, Kurt J. Marfurt, Wookeen ChungAbstract:SUMMARY Geophysicists and applied mathematicians have proposed a rich suite of long-wavelength velocity estimation algorithms to construct starting velocity models for subsequent pre-stack depth migration and inversion. Refraction-traveltime tomography derives subsurface velocity models from picked first-arrival traveltimes. In contrast, Laplace-Domain waveform inversion recovers long-wavelength velocity structure using the weighted amplitudes of first and later arrivals. There are several implementations of first-arrival traveltime inversion, with most based on ray tracing, and some based on the damped monochromatic wave equation, which accurately represent simple and finite-frequency first arrivals. Computationally, Laplace-Domain wavefield inversion is quite similar to refraction-traveltime tomography using damped monochromatic wavefield, but the objective functions used in inversion are radically different. As in classical ray trace-based traveltime inversion, the objective of refraction-traveltime tomography using damped monochromatic wavefield is to match the phase (traveltime) of the first arrival of each measured seismic trace. In contrast, the objective of Laplace-Domain wavefield inversion is to match the weighted amplitudes of both first and later arrivals to the weighted amplitudes of the measured seismic trace. Principles of refraction-traveltime tomography were used to generate velocity models of the earth one century ago. Laplace-Domain waveform inversion is a more recently introduced algorithm and has been less rigorously studied by the seismic research community, with many workers believing it be equivalent to finite-frequency first-arrival traveltime tomography. We show that Laplace-Domain waveform inversion is both theoretically and empirically different from finite-frequency first-arrival traveltime tomography. Specifically, we examine the Jacobian (sensitivity) kernels used in the two inversion schemes to quantify the different sensitivities (and hence the inversion results) of the two methods. Analysing both surface responses and sensitivity results, we show that the Laplace-Domain waveform inversion's sensitivity to later arrivals provides significantly improved resolution of deeper velocity structure than the first-arrival traveltime tomography. We demonstrate this capability using numerical inversion examples using a synthetic five-layer model and the synthetic BP benchmark model. Because of the similar algorithmic structure, Laplace-Domain waveform inversion fits neatly as a starting velocity model pre-processing component of a larger (multi) frequency-Domain wave equation inversion solution package.
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Equivalent source distribution for efficient 3-D acoustic wave equation modelling in the Laplace Domain
Geophysical Journal International, 2011Co-Authors: Sukjoon Pyun, Changsoo Shin, Wookeen ChungAbstract:SUMMARY Since the recent introduction of the Laplace-Domain full waveform inversion, an efficient and accurate modelling technique for the 3-D Laplace-Domain wave equation has been sought. The efficiency and accuracy of the 3-D acoustic wave equation modelling in the Laplace Domain stronglydependsonhowtoaccuratelyaccountforfreesurfaceconditionsandtheactualsource and receiver locations. In terms of efficiency, fortunately, the Laplace-Domain wave equation can be solved on a coarse grid because the field is not propagating as if it were a potential field. However, it is not possible to accurately compute the Laplace-Domain response by assuming that the source and the receivers are located at the grid nodes when we use a coarse grid. To resolve this problem, we propose an equivalent source distribution algorithm that allows us to simulate the free surface condition accurately using a coarse-grid finite-element or finitedifference method. It is shown that the equivalent source vector obtained from a homogeneous half-space model can be used for arbitrarily complex models. The extension of the equivalent source to complex heterogeneous media is explained by the approximation of the Dirac delta function. Numerical tests show that our algorithm is better than the Kaiser windowed sinc function method in the Laplace Domain. Our technique for solving the 3-D Laplace-Domain wave equation can significantly reduce the computational time required for the 3-D LaplaceDomain acoustic full waveform inversion because we can use the coarse grid to accurately simulate conventional marine seismic exploration.
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The Comparison between Refraction-traveltime Tomography and Laplace-Domain Waveform Inversion
73rd EAGE Conference and Exhibition incorporating SPE EUROPEC 2011, 2011Co-Authors: Ho Seuk Bae, Changsoo Shin, Sukjoon Pyun, H. CanlandraAbstract:Since both refraction-traveltime tomography and Laplace-Domain waveform inversion recover long-wavelength velocity structures, both methods are widely used to construct a starting velocity model for full waveform inversion. Unfortunately, the characteristics and theoretical aspects of Laplace-Domain waveform inversion have not been studied as fully as those of refraction-traveltime tomography. Accordingly, it has been suggested that Laplace-Domain waveform inversion is equivalent to refraction-traveltime tomography. However, Laplace-Domain waveform inversion is different from refraction-traveltime tomography in many aspects. From sensitivity images, we can note that the result of refraction-traveltime tomography is significantly affected by anomalies in shallow areas. If we use excessively long offset distances to recover deeper layers, refraction-traveltime tomography fails to delineate not only deep structures but also shallow structures. In Laplace-Domain waveform inversion, on the other hand, it is possible to detect the deeper structures using small Laplace damping constants and long offset distances. From the inversion examples using a synthetic BP model, we observe that refraction-traveltime tomography cannot detect the structures in the deep area, while Laplace-Domain waveform inversion can successfully recover the deep structures in addition to the shallow structures.
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2D Elastic Waveform Inversion in the Laplace Domain
Bulletin of the Seismological Society of America, 2010Co-Authors: Wookeen Chung, Changsoo Shin, Sukjoon PyunAbstract:Abstract There are many obstacles to applying waveform inversion to seismic data. However, the most critical factor is the absence of the low-frequency components that are needed for constructing long-wavelength structure. This problem stems from the highly nonlinear property of waveform inversion, which causes the algorithm to be trapped in a local minimum. The waveform inversion in the Laplace Domain, rather than the usual frequency Domain, is capable of producing velocity models with long-wavelength information. A study on this method was recently published, which was limited to the problem of acoustic media. In this paper, we extend Laplace-Domain waveform inversion to elastic media. Unlike acoustic inversion, elastic inversion requires sophisticated manipulation of the gradient direction. We suggest a method to modify pseudo-Hessian matrices by using a heuristic weighting function. We test our inversion algorithm on synthetic seismic data generated using the Society of Exploration Geophysicists/European Association of Geoscientists & Engineers (SEG/EAGE) salt-dome model and the Commission on Controlled-Source Seismology (CCSS) model. Inversion results using these data sets also produce the long-wavelength velocity model and demonstrate that Laplace-Domain waveform inversion is robust to the initial velocity model. Furthermore, we provide an example showing that our inverted result is a suitable initial model for the frequency-Domain waveform inversion.
Ho Seuk Bae - One of the best experts on this subject based on the ideXlab platform.
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Laplace-Domain waveform inversion versus refraction-traveltime tomography
Geophysical Journal International, 2012Co-Authors: Ho Seuk Bae, Changsoo Shin, Sukjoon Pyun, Kurt J. Marfurt, Wookeen ChungAbstract:SUMMARY Geophysicists and applied mathematicians have proposed a rich suite of long-wavelength velocity estimation algorithms to construct starting velocity models for subsequent pre-stack depth migration and inversion. Refraction-traveltime tomography derives subsurface velocity models from picked first-arrival traveltimes. In contrast, Laplace-Domain waveform inversion recovers long-wavelength velocity structure using the weighted amplitudes of first and later arrivals. There are several implementations of first-arrival traveltime inversion, with most based on ray tracing, and some based on the damped monochromatic wave equation, which accurately represent simple and finite-frequency first arrivals. Computationally, Laplace-Domain wavefield inversion is quite similar to refraction-traveltime tomography using damped monochromatic wavefield, but the objective functions used in inversion are radically different. As in classical ray trace-based traveltime inversion, the objective of refraction-traveltime tomography using damped monochromatic wavefield is to match the phase (traveltime) of the first arrival of each measured seismic trace. In contrast, the objective of Laplace-Domain wavefield inversion is to match the weighted amplitudes of both first and later arrivals to the weighted amplitudes of the measured seismic trace. Principles of refraction-traveltime tomography were used to generate velocity models of the earth one century ago. Laplace-Domain waveform inversion is a more recently introduced algorithm and has been less rigorously studied by the seismic research community, with many workers believing it be equivalent to finite-frequency first-arrival traveltime tomography. We show that Laplace-Domain waveform inversion is both theoretically and empirically different from finite-frequency first-arrival traveltime tomography. Specifically, we examine the Jacobian (sensitivity) kernels used in the two inversion schemes to quantify the different sensitivities (and hence the inversion results) of the two methods. Analysing both surface responses and sensitivity results, we show that the Laplace-Domain waveform inversion's sensitivity to later arrivals provides significantly improved resolution of deeper velocity structure than the first-arrival traveltime tomography. We demonstrate this capability using numerical inversion examples using a synthetic five-layer model and the synthetic BP benchmark model. Because of the similar algorithmic structure, Laplace-Domain waveform inversion fits neatly as a starting velocity model pre-processing component of a larger (multi) frequency-Domain wave equation inversion solution package.
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The Comparison between Refraction-traveltime Tomography and Laplace-Domain Waveform Inversion
73rd EAGE Conference and Exhibition incorporating SPE EUROPEC 2011, 2011Co-Authors: Ho Seuk Bae, Changsoo Shin, Sukjoon Pyun, H. CanlandraAbstract:Since both refraction-traveltime tomography and Laplace-Domain waveform inversion recover long-wavelength velocity structures, both methods are widely used to construct a starting velocity model for full waveform inversion. Unfortunately, the characteristics and theoretical aspects of Laplace-Domain waveform inversion have not been studied as fully as those of refraction-traveltime tomography. Accordingly, it has been suggested that Laplace-Domain waveform inversion is equivalent to refraction-traveltime tomography. However, Laplace-Domain waveform inversion is different from refraction-traveltime tomography in many aspects. From sensitivity images, we can note that the result of refraction-traveltime tomography is significantly affected by anomalies in shallow areas. If we use excessively long offset distances to recover deeper layers, refraction-traveltime tomography fails to delineate not only deep structures but also shallow structures. In Laplace-Domain waveform inversion, on the other hand, it is possible to detect the deeper structures using small Laplace damping constants and long offset distances. From the inversion examples using a synthetic BP model, we observe that refraction-traveltime tomography cannot detect the structures in the deep area, while Laplace-Domain waveform inversion can successfully recover the deep structures in addition to the shallow structures.
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2D acoustic-elastic coupled waveform inversion in the Laplace Domain
Geophysical Prospecting, 2010Co-Authors: Ho Seuk Bae, Changsoo Shin, Young Ho Cha, Yunseok Choi, Dong-joo MinAbstract: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 frequencyDomain 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 acousticelastic 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 finiteelement 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.
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2D acoustic-elastic coupled waveform inversion in the Laplace Domain
Geophysical Prospecting, 2010Co-Authors: Ho Seuk Bae, Changsoo Shin, Young Ho Cha, Yunseok Choi, Dong-joo MinAbstract: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. © 2010 European Association of Geoscientists & Engineers
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2-D Waveform inversion in the Laplace Domain for acoustic-elastic coupled media
SEG Technical Program Expanded Abstracts 2010, 2010Co-Authors: Ho Seuk Bae, Changsoo Shin, Dong-joo Min, Henri CalandraAbstract:Summary The waveform inversion in the time or frequency Domain has a highly nonlinear characteristic resulting from many local minima. Furthermore, in the absence of low frequencies in real exploration data, it is difficult to restore long-wavelength structures using a time or frequency Domain waveform inversion algorithm. Recently, an acoustic waveform inversion algorithm in the Laplace Domain emerged to restore long-wavelength structures, playing a key role in imaging subsurface structures and velocity inversions, even if low frequencies are absent. This Laplace-Domain inversion algorithm mitigates local minima problems in the inversion procedure. We extended the Laplace-Domain waveform inversion to acoustic-elastic coupled media. We applied our algorithm to the synthetic example of a 2D elastic model containing a flat water layer, which is modified from the SEG/EAGE salt model. From the numerical example, we claim that the Laplace-Domain waveform inversion, which generates long-wavelength structures of the true model for acoustic-elastic coupled media, would be a method that provides a good initial velocity model for frequency-Domain waveform inversion.
Ho-young Lee - One of the best experts on this subject based on the ideXlab platform.
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Source estimation and direct wave reconstruction in Laplace-Domain waveform inversion for deep-sea seismic data
Geophysical Journal International, 2011Co-Authors: Nam-hyung Koo, Changsoo Shin, Dong-joo Min, Keun-pil Park, Ho-young LeeAbstract:SUMMARY We propose a strategy to overcome the high sensitivity to early-time noise of the Laplace-Domain waveform inversion. In deep-sea seismic data, this problem is particularly crucial to obtaining accurate velocity structures. To this end, rather than simply filtering or muting early-time data, we propose replacing the original, noise-contaminated direct waves with analytically computed noise-free waves. To reconstruct the noise-free direct waves, we compute Green's functions for half-space media, estimate the source wavelet from the original direct waves using the full Newton method in the frequency Domain and then convolve the Green's functions with the estimated source wavelet. The data obtained by merging the reconstructed direct waves with the original late-time data set can then be used for Laplace- and Laplace-Fourier-Domain waveform inversions. To verify the source estimation and direct wave reconstruction strategy, we applied it to field data acquired in a deep-sea environment and obtained a realistic 2-D velocity model. The source estimation and direct wave reconstruction methods can also be applied to 3-D Laplace-Domain waveform inversion.
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Source Estimation And Direct Wave Reconstruction For the Laplace-Domain Waveform Inversion of Deepwater Seismic Data
SEG Technical Program Expanded Abstracts 2010, 2010Co-Authors: Nam-hyung Koo, Mrinal Shin, Dongkweon Lee, Keun-pil Park, Ho-young LeeAbstract:We propose an alternative strategy for overcoming the high sensitivity of the Laplace-Domain waveform inversion to early time noises, especially of deepwater seismic data. We estimate the source wavelet from the raw direct wave using the full Newton method in the frequency Domain and reconstruct the direct wave without noise using the estimated source wavelet and the Green’s function in a constant velocity medium. The data set adequate for the Laplace-Domain waveform inversion can be made by merging the reconstructed direct wave with the original data set without direct wave. Our strategy is applied to field data from deepwater environments and a realistic velocity model can be recovered from the Laplace-Domain waveform inversion of the reconstructed seismic data.
