735 research outputs found
An overview of Marchenko methods
No full textSince the introduction of the Marchenko method in geophysics, many variants have been developed. Using a compact unified notation, we review redatuming by multidimensional deconvolution and by double focusing, virtual seismology, double dereverberation and transmission-compensated Marchenko multiple elimination, and discuss the underlying assumptions, merits and limitations of these methods.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Applied Geophysics and Petrophysic
Plane-Wave Marchenko Imaging Method: Field Data Application
No full textSeismic imaging is often used to interpret subsurface formations. However, images obtained by conventional methods are contaminated with internal multiples. The Marchenko method provides the means to obtain multiple-free subsurface images. Due to the high computational cost of the conventional point-source Marchenko imaging method, the less expensive plane wave Marchenko imaging method can be used to produce subsurface images along planes. This method can be repeated for different incident angles to produce images that account for the variable dip of the subsurface structures. In this abstract, we present the results of applying the plane wave Marchenko imaging method to a 2D marine dataset over the Vøring basin, the North Sea. The results show that, in comparison to the conventional plane-wave image, the plane-wave Marchenko imaging method successfully suppressed internal multiples, resulting in improvements in both the amplitude and continuity of the seismic events.Accepted Author ManuscriptApplied Geophysics and PetrophysicsImPhys/Medical Imagin
Adaptive Marchenko internal multiple attenuation
No full textCuriosity regarding what we cannot see has always driven research. Science has helped us to uncover many of those hidden secrets. In particular, geophysics has helped us to image the inside of the Earth. By sending a seismic signal into the Earth and recording the signal that comes back, geophysicists can characterize the layers of the subsurface. Nowadays, geophysics is used for many purposes, for example, the localization of fossil fuels, the characterization of the subsurface for the construction of wind farms and the evaluation of reservoirs for geothermal energy. In order to decrease the risk and cost involved in these activities, we need images of the subsurface that are as accurate as possible. These images can only be obtained if we fully understand the propagation of the seismic signal in the subsurface. A long-standing problem in geophysical imaging is the presence of internal multiple reflections. When imaging the subsurface, we assume that the signal only reflects once when there is a contrast in velocity and/or density (for example, when changing from sand to rock). However, in reality, the signal can reflect many times inside the subsurface before being recorded at the surface. When treating the arrivals that have reflected many times as arrivals that have only reflected once, we incorrectly image the subsurface and create ghost reflectors that do not exist. This problem is particularly strong in geological settings that have a complex structure with many strong velocity and/or density contrasts above an area of interest. This may happen, for example, when there is a reservoir of oil below a thick stratified salt layer. In such cases, the image of the area of interest is unreliable due to the presence of many ghost reflectors. Therefore, we have to use knowledge of wave propagation to predict and attenuate the internal multiples in the data prior to imaging.In this thesis, I further develop the data-driven and wave-equation-based Marchenko method to make it suitable for the attenuation of internal multiples in seismic field data. In addition, I evaluate the performance of suitable methods by applying them to field datasets recorded in different geological settings. I start this evaluation by demonstrating that what we call the conventional Marchenko method is perhaps not the most suitable Marchenko method for the application to field data. I develop an alternative Marchenko method instead: the adaptive double-focusing method. I show that this method indeed produces improved results compared to the conventional Marchenko method when applying it to a line of 2D data of the Santos Basin, Brazil. Since the 2D results show promise, I continue with the extension to 3D applications. I first identify the key acquisition parameters that affect the result of our Marchenko method on 3D synthetic data and conclude that the limited crossline aperture and the coarse sail line spacing have the strongest effect on the quality of the result. Based on this evaluation, I interpolate the sail line spacing on 3D field data acquired in the Santos Basin and use the adaptive double-focusing method to predict and subtract internal multiples. I conclude that 3D Marchenko internal multiple attenuation seems to be sufficiently robust for the application to narrow azimuth streamer data in a deep marine setting, provided that there is sufficient aperture in the crossline direction and that the sail lines are interpolated. In addition, the adaptive double-focusing method is suitable for the attenuation of internal multiples generated by a complex overburden and for simultaneously redatuming to a level below this overburden. Next, I modify the adaptive double-focusing method to obtain an adaptive double dereverberation method that is suitable when only aiming to attenuate internal multiples generated in an overburden without redatuming. Moreover, this method does not require a velocity model. I apply this method to a 2D line of data acquired in the very shallow Arabian Gulf. Also, I assess how to meet the data requirements for the Marchenko method in shallow water environments (e.g., the removal of surface-related multiples, the deconvolution of the source signature) and demonstrate that the state-of-the-art Robust Estimation of Primaries by Sparse Inversion (R-EPSI) method is capable of producing the correct input data for the Marchenko method in such settings. Subsequently, I discuss the role of the adaptive filter in the application of the Marchenko method to field data. I argue that developments in seismic data processing allow us to predict internal multiples with more accuracy, such that only a conservative adaptive filter is needed to correct for the unavoidable minor amplitude and phase discrepancies between the internal multiples in the data and the predicted internal multiples. I demonstrate this by using a conservative adaptive filter to subtract internal multiples that were predicted by applying an adaptive Marchenko multiple elimination method to a 2D line of field data acquired in the Norwegian North Sea. Finally, based on the results presented in this thesis, I conclude that the Marchenko method is an effective, data-driven and robust method for the prediction of internal multiples in marine seismic data. Different Marchenko methods are suitable for different purposes. There are two key elements for the successful application of a Marchenko method to field data: 1) the acquisition geometry needs to be sufficiently dense and 2) a careful processing workflow needs to be constructed that accounts for the specifics of the geological setting at hand, with significant emphasis on amplitude and phase preservation.Applied Geophysics and Petrophysic
Iphidozercon altaicus Gwiazdowicz & Marchenko 2012, sp. n.
No full textIphidozercon altaicus sp. n. (Figs 1–4) <p>Description. Female (N = 3). Dorsum (Fig. 1). Dorsal shield oval, length 375–380 µm, width 230–250 µm distinct foveate sculpture throughout. 18 pairs of setae on podonotal part of shield and 14 pairs of setae on opisthonotal part of shield. All setae fine, smooth and pointed, length of 25–30 µm, except j1 (10 µm, inserted ventrally), and two antero-lateral setae s1, s2 (15 µm).</p> <p>Venter (Fig. 2) Tritosternum with trapezoidal base (25 µm) and finely pilose laciniae (35 µm). Sternal shield rectangular, 70 × 55 µm, setae st1–st3 smooth and pointed, length 10 µm. Metasternal setae st4 (10 µm) on soft membrane. Genital shield small and narrow (55 µm), spatulate posteriorly. Genital setae st5 (15 µm) outside the shield. Anal shield relatively large 60 µm long, 70 µm wide with para-anal setae (15 µm) and post-anal seta (20 µm). Narrow cribrum below post-anal seta. Sternal, genital and anal shields are unornamented. Peritremes ending anteriorly to coxae I, stigmata at level of coxae IV. Peritremal shields wide, with weak posterior lineate ornamentation. Opisthogastric integument behind coxae IV with one pair of oval metapodal plates, a pair of smaller plates near posterior ends of peritrematal shields. Opisthogastric setae JV1–JV5, ZV1–ZV2 15 µm long, others (R2–R4) approximately 20 µm.</p> <p>Gnathosoma. Hypostome with robust horn-like corniculi and four pairs of setae. Anterior seta h1 longest (30 µm), internal seta h3 (20 µm), palp coxal seta h4 (25 µm) shorter, external seta h2 (10 µm) shortest. Seven transverse rows of hypostomal denticles present, numbers of denticles per row (anterior to posterior) 12, 15, 17, 15, 17, 16, 13 (Fig. 3a). Chelicera typical of genus, fixed digit with three teeth, movable digit with two teeth (Fig. 3b), other details of chelicerae not visible in available specimens. Epistome with central prong longest, lateral prongs shorter, with denticulate outer margins (Fig. 3c).</p> <p>Legs and palps. Lengths of legs: I – 230 µm, II – 200 µm, III – 180 µm, IV – 210 µm. Setation of genua I–II–III–IV: 12–10–7–7 (Fig. 4a); tibiae 12–9–7–7 (Fig. 4b). Tarsus II to IV each with the dorsoproximal setae ad2 and pd2 short and straight (Fig 4c). Palp apotele 2-tined.</p> <p> Material examined: Holotype: Female. Russia, North-East of Altai Mountains, Teletskoe lake region, environs of Obogo village, in litter of <i>Betula pubescens – Populus tremula</i> forest, (51°30’48’’ N, 87°18’7’’ E, 900 m a.s.l.), 6 August 2007, leg. I.I. MARCHENKO. Paratypes: 2 females, North-East of Altai Mountains, Teletskoe lake region, environs of Obogo village, in litter of <i>Abies sibirica – Pinus sibirica</i> forest, (51°30’48’’N, 87°18’7’’E, 900 m a.s.l.), 6 August 2007, leg. I. I. MARCHENKO.</p> <p>Etymology. The name of this species reflects the fact that it was collected in the Altai Mountains.</p> <p> Differential diagnosis. <i>Iphidozercon altaicus</i> sp. n. is similar to <i>Iphidozercon foveatus</i> GWIAZDOWICZ et HALLIDAY, 2008. Both species have foveate sculpture on the dorsal shield and similar lengths of dorsal setae. The length of peritreme and the shape of genital shield is similar in both species. Nevertheless, many differences have been detected, such as shapes of the peritremal and anal shields. In <i>I. foveatus</i> the anal shield is narrow, while in <i>I. altaicus</i> it is wider than long. In <i>I. foveatus</i> the peritremal shield is wide, with tiny denticles on the internal side and in <i>I. altaicus</i> the shield is narrower and without denticles. In <i>I. foveatus</i> five pairs of smaller platelets bearing pores are located on the ventral side, in <i>I. altaicus</i> there are no such platelets. In <i>I. foveatus</i> the epistome has a central elongated prong ending in three denticles, but in <i>I. altaicus</i> the prong ends in spikes. In <i>I. foveatus</i> the movable digit has three teeth, but in <i>I. altaicus</i> it has two teeth.</p>Published as part of <i>Gwiazdowicz, D. J. & Marchenko, I. I., 2012, Two New Species Of Iphidozercon (Acari: Ascidae) With A Key To Females, pp. 41-52 in Acta Zoologica Academiae Scientiarum Hungaricae 58 (1)</i> on pages 42-44, DOI: <a href="http://zenodo.org/record/5732065">10.5281/zenodo.5732065</a>
Investigating the robustness of Green’s function retrieval via Marchenko focusing and Seismic Interferometry
No full textSeismic interferometry and Marchenko focusing are alternative techniques to retrieve the Green’s function between a virtual source in the subsurface and receivers at the surface. Seismic interferometry requires the presence of a receiver in the subsurface at the position of the virtual source, while Marchenko focusing utilizes only the reflection measurements at the Earth’s surface and an estimate of the direct wave from the virtual source to the acquisition level. I find that, for both methodologies, limited recording aperture of the acquisition array is a strong limiting factor when trying to retrieve events caused by interactions with curved scattering objects in the subsurface. It is also established that, given the dense sampling of the wave field, applying the Marchenko focusing scheme provides a more accurate retrieval of the Green’s functions in such scenarios. However, if the source and receiver arrays are subsampled, Marchenko focusing provides less robust retrieval of the accurate subsurface fields. Marchenko focusing also has more severe requirements on the reflection response. When an erroneous scaling of the amplitudes and/or a constant phase-shift is introduced the method fails to retrieve accurate subsurface wave fields without artifacts caused by internal multiples. I propose a workflow to calibrate the reflection response, prior to Green’s function retrieval via Marchenko focusing, using additional information in the form of a VSP dataset. First a virtual VSP dataset is estimated via Marchenko focusing, to subsequently compare its upgoing component to the upgoing part of the recorded VSP. Thereby, making it possible to correct for a constant phase shift applied to the reflection data. By identifying the minimum residual energy between the virtual VSP and the recorded VSP wave fields, an erroneous scaling of the reflection response can also be corrected. This workflow leads to a more robust Marchenko focusing approach where the reflection response can be redatumed to a target zone in the subsurface: the resulting ghost-free gathers, and ultimately images of the subsurface, show more illumination and improved resolution, leading to better delineation of thin stratigraphy as well as faulted structures.Civil Engineering and GeosciencesGeoscience & EngineeringMaster in Applied Geophysics - IDEA Leagu
The role of ubiquitination in the direct mitochondrial death program of p53
No full textp53 ubiquitination at C-terminal lysines by MDM2 and other E3 ligases had been considered a straightforward negative regulation of p53 with only one function, that is marking the protein for proteasomal degradation. In this review, we will focus on the recently uncovered activating role of ubiquitination in the transcription-independent direct mitochondrial death program of p53
Marchenko imaging by unidimensional deconvolution
No full textObtaining an accurate image of the subsurface still remains a great challenge for the seismic method. Migration algorithms aim mainly on positioning seismic events in complex geological contexts. Multiple reflections are typically not accounted for in this process, which can lead to the emergence of artefacts. In Marchenko imaging, we retrieve the complete up- and downgoing wavefields in the subsurface to construct an image without such artefacts. The quality of this image depends on the type of imaging condition that is applied. In this paper, we propose an imaging condition that is based on stabilized unidimensional deconvolution. This condition is computationally much cheaper than multidimensional deconvolution, which has been proposed for Marchenko imaging earlier. Two specific approaches are considered. In the first approach, we use the full up- and downgoing wavefields for deconvolution. Although this leads to balanced and relatively accurate amplitudes, the crosstalk is not completely removed. The second approach is to incorporate the initial focussing function in the deconvolution process, in such a way that the retrieval of crosstalk is avoided. We compare images with the results of the classical cross-correlation imaging condition, which we apply to reverse-time migrated wavefields and to the up- and downgoing wavefields that are retrieved by the Marchenko method.Accepted Author ManuscriptImPhys/Acoustical Wavefield Imagin
The role of ubiquitination in the direct mitochondrial death program of p53
No full textp53 ubiquitination at C-terminal lysines by MDM2 and other E3 ligases had been considered a straightforward negative regulation of p53 with only one function, that is marking the protein for proteasomal degradation. In this review, we will focus on the recently uncovered activating role of ubiquitination in the transcription-independent direct mitochondrial death program of p53
Marchenko redatuming, imaging and multiple elimination, and their mutual relations
No full textWith the Marchenko method it is possible to retrieve Green's functions between virtual sources in the subsurface and receivers at the surface from reflection data at the surface and focusing functions. A macro model of the subsurface is needed to estimate the first arrival; the internal multiples are retrieved entirely from the reflection data. The retrieved Green's functions form the input for redatuming by multidimensional deconvolution (MDD). The redatumed reflection response is free of internal multiples related to the overburden. Alternatively, the redatumed response can be obtained by applying a second focusing function to the retrieved Green's functions. This process is called Marchenko redatuming by double focusing. It is more stable and better suited for an adaptive implementation than Marchenko redatuming by MDD, but it does not eliminate the multiples between the target and the overburden. An attractive efficient alternative is plane-wave Marchenko redatuming, which retrieves the responses to a limited number of plane-wave sources at the redatuming level. In all cases, an image of the subsurface can be obtained from the redatumed data, free of artefacts caused by internal multiples. Another class of Marchenko methods aims at eliminating the internal multiples from the reflection data, while keeping the sources and receivers at the surface. A specific characteristic of this form of multiple elimination is that it predicts and subtracts all orders of internal multiples with the correct amplitude, without needing a macro subsurface model. Like Marchenko redatuming, Marchenko multiple elimination can be implemented as an MDD process, a double dereverberation process, or an efficient plane-wave oriented process. We systematically discuss the different approaches to Marchenko redatuming, imaging and multiple elimination, using a common mathematical framework
Interbed demultiple using Marchenko redatuming on 3D field data of the Santos basin
No full textWe apply Marchenko redatuming using an adaptive double-focusing method to 3D field data of the Santos basin, Brazil. This method was already successfully applied to 2D field data and we now study the acquisition geometry and preprocessing requirements in 3D. We start from 3D synthetic data modeled on a dense grid of colocated sources and receivers and decimate down to a realistic NAZ streamer acquisition. The synthetic tests show that the sail line spacing and the missing outer cables are the acquisition parameters with the strongest effect on Marchenko redatuming. We can interpolate for the sail line spacing and the near offsets, but the missing outer cables are unfortunately a limitation of the acquisition. After applying the proposed interpolation to 3D field data, interbed multiples are successfully predicted and subtracted from the target area, resulting in a significant improvement in the geological interpretation. Naturally, the pre-processing requirements and challenges strongly depend on the acquisition geometry and the geology of the area under investigation (e.g. water depth, shape of the overburden, maximum dip). Hence, these tests only give a general idea about the limitations of 3D Marchenko redatumingAccepted author manuscriptApplied Geophysics and PetrophysicsImPhys/Acoustical Wavefield Imagin
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