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Collaborating Authors
Results
ABSTRACT We present an interferometric interpretation of the iterative Marchenko scheme including both free-surface multiples and internal multiples. Cross-correlations are used to illustrate the combination of causal and acausal events that are essential for the process of multiple removal. The first 4 steps in the scheme are discussed in detail, where the effect of different contributions on the result is displayed and the formation of individual events is illustrated. We highlight the events that are necessary to understand the process that removes both internal multiples and free-surface multiples from the data. We demonstrate that additional contributions are needed to correct for the presence of free-surface multiples. Presentation Date: Monday, October 17, 2016 Start Time: 3:45:00 PM Location: 147/154 Presentation Type: ORAL
Electromagnetic Marchenko imaging in 1D for dissipative media
Zhang, Lele (Delft University of Technology) | Slob, Evert (Delft University of Technology, Delphi Consortium) | Van Der Neut, Joost (Delft University of Technology, Delphi Consortium) | Wapenaar, Cornelis (Delft University of Technology, Delphi Consortium)
ABSTRACT We present a one-dimensional lossless scheme to compute an image of a dissipative medium from two single-sided reflection responses. One reflection response is measured at or above the top reflector of a dissipative medium and the other reflection response is computed as if measured at or above the top reflector of a medium with negative dissipation which we call the effectual medium. These two reflection responses together can be used to construct the approximate reflection data of the corresponding lossless medium by multiplying and taking the square root in time domain. The corresponding lossless medium has the same reflectors as the dissipative medium. Then the constructed reflection data can be used to compute the focusing wavefield which focuses at the chosen location in subsurface of the dissipative medium. From the focusing function and constructed reflection response the Green’s function for a virtual receiver can be obtained. Because the up- and downgoing parts of the Green’s function are retrieved separately, these are used to compute the image. We show with an example that the method works well for a sample in a synthesized waveguide that could be used for measurements in a laboratory. Presentation Date: Wednesday, October 19, 2016 Start Time: 10:20:00 AM Location: Lobby D/C Presentation Type: POSTER
ABSTRACT We propose a novel acoustic decomposition operator for time slices, loosely based on conventional surface decomposition operators. The proposed operators hold for constant velocity models and require two 2D Fourier Transforms (one forward, one backward) per decomposed time slice per decomposition direction. We then demonstrate the capabilities of our operators on a constant velocity model and the Marmousi model. The decomposition results prove that we can decompose into up-, down-, left- and right-going waves for complex velocity media. Presentation Date: Thursday, October 20, 2016 Start Time: 9:20:00 AM Location: 171/173 Presentation Type: ORAL
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling (0.88)
From closed-boundary to single-sided homogeneous Green's function representations
Wapenaar, Cornelis (Delft University of Technology) | Thorbecke, Jan (Delft University of Technology) | Van Der Neut, Joost (Delft University of Technology, Delphi Consortium) | Slob, Evert (Delft University of Technology, Delphi Consortium) | Singh, Satyan (University of the West Indies)
ABSTRACT The homogeneous Green’s function (i.e., the Green’s function and its time-reversed counterpart) plays an important role in optical, acoustic and seismic holography, in inverse scattering methods, in the field of time-reversal acoustics, in reverse-time migration and in seismic interferometry. Starting with the classical closed-boundary representation of the homogeneous Green’s function, we modify the configuration to two parallel boundaries. We discuss step-by-step a process that eliminates the integral along the lower boundary. This leads to a single-sided representation of the homogeneous Green’s function. Apart from imaging, we foresee interesting applications in inverse scattering, time-reversal acoustics, seismic interferometry, passive source imaging, etc. Presentation Date: Monday, October 17, 2016 Start Time: 1:25:00 PM Location: 147/154 Presentation Type: ORAL
Beyond Marchenko: Obtaining virtual receivers and virtual sources in the subsurface
Singh, Satyan (University of the West Indies) | Wapenaar, Cornelis (Delft University of Technology, Delphi Consortium) | Van Der Neut, Joost (Delft University of Technology, Delphi Consortium) | Snieder, Roelof (Colorado School of Mines)
ABSTRACT By solving the Marchenko equations, the Green’s function can be retrieved between a virtual receiver in the subsurface to points at the surface (no physical receiver is required at the virtual location). We extend the idea of these equations to retrieve the Green’s function between any two points in the subsurface; i.e, between a virtual source and a virtual receiver (no physical source or physical receiver is required at either of these locations). This Green’s function is called the virtual Green’s function and includes all the primaries, internal and free-surface multiples. Similar to the Marchenko Green’s function, we require the reflection response at the surface (single-sided illumination) and an estimate of the first arrival travel time from the virtual location to the surface. Presentation Date: Monday, October 17, 2016 Start Time: 3:20:00 PM Location: 147/154 Presentation Type: ORAL
- North America > United States (0.28)
- Europe (0.28)
ABSTRACT We present a scheme for Marchenko imaging in a dissipative heterogeneous medium. The scheme requires measured reflection and transmission data at two sides of the dissipative medium. The effectual medium is the same as the dissipative medium, but with negative dissipation. We show how the measured double-sided data can be combined to obtain the single-sided reflection response of the effectual medium. Two sets of single-sided Marchenko equations follow that are used to compute to the focusing wavefield and the Green functions. Each uses single-sided reflection responses of the dissipative and effectual medium. To start the solution for these equations an initial estimate of the dissipation is required in addition to the estimate of the travel time of the first arrival. Avoiding the estimate of dissipation of the first arrival in a low-loss medium does not have a detrimental effects on the image quality. The numerical example shows the effectiveness of this strategy. Presentation Date: Monday, October 17, 2016 Start Time: 2:15:00 PM Location: 147/154 Presentation Type: ORAL
Marchenko wavefield redatuming, imaging conditions, and the effect of model errors
de Ridder, Sjoerd (University of Edinburgh) | Curtis, Andrew (University of Edinburgh) | Van Der Neut, Joost (Delft University of Technology, Delphi Consortium) | Wapenaar, Cornelis (Delft University of Technology, Delphi Consortium)
ABSTRACT Recently, a novel method to redatum the wavefield in the sub-surface from a reflection response measured at the surface has gained interest for imaging primaries in the presence of strong internal multiples. A prerequisite for the algorithm is an accurate and correct estimate of the direct-wave Green's function. However, usually we use an estimate for the direct-wave Green's function computed in a background velocity medium. Here, we investigate the effect of amplitude and phase errors in that estimate. We formulate two novel imaging conditions based on double-focusing the measured reflection response inside the subsurface. These yield information on the amplitude error in the estimate for the direct-wave Green's function which we can then correct, but the phase error remains elusive. Presentation Date: Monday, October 17, 2016 Start Time: 1:50:00 PM Location: 147/154 Presentation Type: ORAL