Search

Seismic processing and imaging workflows have been refined over many decades to attenuate aspects of the recorded wavefield which would be improperly mapped into the image domain by legacy migration algorithms such as Kirchhoff prestack depth migration. These workflows, which include techniques such as deghosting, designature, demultiple, and regularization, have become increasingly complex and time-consuming due to the sequential fashion in which they must be tested and applied. The single-scattering (primary-only) preprocessed data are then migrated and used in extensive model building workflows, including reflection residual moveout tomography, to refine low-frequency subsurface models. Obtaining optimal results at each stage requires subjective assessment of a wide range of parameter tests. Results can be highly variable, with different decisions resulting in very different outcomes. Such workflows mean that projects may take many months or even years. Full-waveform inversion (FWI) imaging offers an alternative philosophy to this conventional approach. FWI imaging is a least-squares multiscattering algorithm that uses the raw field data (transmitted and reflected arrivals as well as their multiples and ghosts) to determine many different subsurface parameters, including reflectivity. Because this approach uses the full wavefield, the subsurface is sampled more completely during the inversion. Here, we demonstrate the application of a novel multiparameter FWI imaging technique to generate high-resolution amplitude variation with angle reflectivity simultaneously with other model parameters, such as velocity and anisotropy, directly from the raw field data. Given that these results are obtained faster than the conventional workflow with a higher resolution, improved illumination, and reduced noise, we highlight the potential of multiparameter FWI imaging to supersede the conventional workflow.

Quantitative investigations of ancient source-to-sink systems usually provide insights into either instantaneous conditions or mean conditions. Field-based channel palaeohydraulic approaches effectively recover instantaneous water discharges and sediment fluxes, whereas catchment- and regional-scale modelling approaches often recover mean annual water discharges and sediment fluxes, or mean discharges and fluxes on longer, million-year timescales. There is a critical gap between these timescales of investigation which reflects the intermittency of flow and sediment transport. However, at present, this gap is difficult to reconcile. In ancient source-to-sink systems, constraining the intermittency of flow and sediment transport is necessary to reconstruct water discharges and sediment fluxes and, therefore, investigate: (1) magnitudes and characteristics of ancient floods; (2) river behaviour in warmer palaeoclimates; (3) river response to climatic perturbation; and (4) catchment hydroclimate. Intermittency constraints are therefore crucial to decipher how landscapes evolved in response to tectonic and climatic forcing in the geological past. Here we take a multi-proxy approach to address this challenge. We combine fluvial stratigraphic datasets, flow and sediment transport models, and general circulation model (GCM) results to develop new methods to constrain intermittency in ancient source-to-sink systems. We illustrate these methods for ancient systems preserved in the Turonian Ferron Sandstone, USA, which records a Cretaceous greenhouse climate, and the Paleocene–Eocene Esplugafreda Formation and Claret Formation, Spain, which record the Paleocene–Eocene Thermal Maximum. To evaluate our methods, we compare our intermittency estimates with facies observations that reflect discharge regime and surface runoff regime, as well as terrestrial palaeoclimate proxies. We find these methods are effective and, further, we outline the necessary next steps to advance these methods. Our results demonstrate the potential to use multidisciplinary datasets to constrain intermittency and, therefore, the dynamics and evolution of ancient source-to-sink systems in response to tectonic and climatic forcing. Further, with continual advances in the use of GCMs to model palaeoclimates, our results highlight the potential to use GCMs to explore water discharges and sediment fluxes in systems where the rock record is incomplete or inaccessible.

Understanding how sedimentary rocks represent time is one of the significant challenges in sedimentology. Sedimentation rates retrieved from vertical sections are strongly timescale dependent, which means that we cannot use empirical rate data derived from vertical sections in modern environments to interpret the temporal structure of ancient sedimentary deposits. We use the Lower to Middle Campanian Blackhawk Formation deposits in eastern Utah and western Colorado as a natural laboratory to test a source-to-sink methodology circumventing this timescale dependence by relating modern progradation rates to the deltaic shoreline progradation of ancient siliciclastic rocks. Our objective is to quantify how much time is needed to account for the observed cumulative deltaic shoreline progradation recorded by the shallow-marine sandstone bodies of the Blackhawk Formation in terms of progradation rates derived from comparable modern deltaic systems. By making the simplifying assumption that the Blackhawk Formation rocks were deposited along a linear coastline that only grew by aggradation and progradation, it is possible to argue that the stratigraphic completeness of two-dimensional dip-oriented stratigraphic cross-sections through these deposits should be high. Furthermore, we hypothesise that delta progradation estimates capture a significant portion of the biostratigraphically and radiometrically constrained duration of the succession. By comparing the recorded progradation with modern progradation rates, we estimate that we need ca. 20% (median value, with minimum and maximum estimates of 2% and 300%) of the time available from biostratigraphic and radiometric dating to account for the progradation recorded by the sedimentary deposits. This indicates that long-term progradation rates averaged over the entire duration of the Blackhawk Formation were only a factor of five times slower than the modern progradation rates derived from observations over periods that are five to six orders of magnitude shorter. We conclude that a significant amount of time is represented by prograding deltaic shoreline deposits and that by considering the cumulative shoreline progradation, we could limit the effects of timescale dependence on the rate estimates used in our analysis. publishedVersion

The flavor of this "Impact" department is somewhat different. In a pandemic, everybody has to come together. In April 2020, a call went out in the United Kingdom for groups to informally form and collaborate to study this brutal pathogen in whatever way they could. The five authors of this article, old friends from the geophysical industry with decades of experience in numerical modeling and big data, formed such a group.

Estimating [Formula: see text] using downgoing waves in zero-offset vertical seismic profiles (VSPs) can be challenging when scattered waves from near-borehole heterogeneities interfere with direct arrivals. In any [Formula: see text] estimation method that assumes a downgoing plane wave, constructive and destructive wave-mode interference can cause errors in the estimate. For example, in the spectral-ratio method, such interference modulates the amplitude spectra introducing significant variations and even nonphysical negative [Formula: see text] (amplification) estimates. We have investigated this phenomenon using synthetic and field data sets from offshore Australia and developed a two-step waveform-based method to characterize scattering anomalies and improve [Formula: see text] estimates. Waveform information is key to deal with closely spaced band-limited seismic events. First, we solve an inverse problem to locate and characterize scatterers by minimizing the traveltime and waveform misfits. Then, using the estimated parameters, we model the scatterers’ contribution to the VSP data and remove it from the observed waveforms. The resulting spectra resemble those that would have been acquired in the absence of the scatterers and are much more suitable for the spectral-ratio method. By assuming a 1D medium and a simple scatterer shape (i.e., circular), we parameterize a scattering heterogeneity using five parameters (depth, distance, size, velocity, and density) and seek a solution using a grid search to handle the nonuniqueness of the VSP inversion. Instead, adaptive subtraction is required to fine-tune the modeled interference to better fit the observation. We successfully use this method to characterize and mitigate the strongest wave interference in the field data. The final [Formula: see text] estimates contain milder variations and much less nonphysical negative [Formula: see text]. Our results demonstrate that the proposed method, readily extendible to multiple scatterer cases, can locate discrete scatterers, remove the effects of their interference, and thus significantly improve the [Formula: see text] estimates from VSP data.

Summary So-called “blended” seismic data acquisition has enjoyed increasing popularity recently because it is realising some of the potential economic and spatial sampling benefits it promised. However, actuations of seismic sources (“shots”) that overlap in time currently need to be separated (deblended) so that they can be processed as if they had been acquired without overlap. When a shot is fired on top of weak signal from an earlier shot, recovery of the weak signal is a well-known significant challenge.

Summary Images constructed from up-coming wavefields can be very effectively deconvolved using up/down deconvolution, however, they have geometry related drawbacks that reduce the quality of the shallower zones. In contrast, the down-going wavefield, which is imaged using mirror imaging, does not suffer from such geometry related disadvantages, however, it lacks a powerful deconvolution technique akin to up/down deconvolution. We use a modified Delft feedback model to describe the up- and down-going scattered wavefields. Using these results, we illustrate how up/down deconvolution works and then go on to introduce a new idea called down/down deconvolution. This new technique inverts the down-going wavefield for the Earth’s response in the absence of a free-surface. The free-surface multiples are removed and the 3D source wavefield is deconvolved to produce a result that is theoretically the same as up/down deconvolution. As a result we can combine the geometrical advantages of the down-going wavefield and the benefits of a powerful deconvolution technique. We illustrate this new idea using a synthetic dataset and a real 3D OBN dataset from the North Sea.

In siliciclastic and carbonate reservoirs, depositional facies are often described as being organized in cyclic successions that are overprinted by diagenesis. Most reservoir modelling workflows are not able to reproduce stochastically such patterns. Herein, a novel geostatistical method is developed to model depositional facies architectures that are rhythmic and cyclic, together with superimposed diagenetic facies. The method uses truncated Pluri-Gaussian random functions constrained by transiograms. Cyclicity is defined as an asymmetric ordering between facies, and its direction is given by a three-dimensional vector, called shift. This method is illustrated on two case studies. Outcrop data of the Triassic Latemar carbonate platform, northern Italy, are used to model shallowing-upward facies cycles in the vertical direction. A satellite image of the modern Bermuda platform interior is used to model facies cycles in the windward-to-leeward lateral direction. As depositional facies architectures are modelled using two Gaussian random functions, a third Gaussian random function is added to model diagenesis. Thereby, depositional and diagenetic facies can exhibit spatial asymmetric relations. The method is applied in two regions of the Latemar carbonate platform that experience two different types of diagenetic transformation: syn-depositional dolomite formation, and post-depositional fracture-related diagenesis. The method can also incorporate proportion curves to model non-stationary facies proportions. This is illustrated in Cretaceous shallow-marine sandstones and mudstones, Book Cliffs, Utah, for which cyclic facies and diagenetic patterns are constrained by embedded transition probabilities.

SUMMARY One of the aims of time-lapse seismic feasibility studies is to determine whether a desired time-lapse signal is distinguishable from incoherent noise. Acquisition parameters play a key role in repeatability, with sourcereceiver positioning errors commonly being regarded as the most important issue. A normalised root-mean-square (NRMS) variogram analysis measures the effect of source-receiver geometry differences on observed nonrepeatability of traces. The overall trend of the variogram is strongly controlled by the heterogeneous characteristics of the overburden. We investigate the influence of heterogeneity on seismic repeatability using a NRMS variogram on synthetic data. We generate synthetic seismic data (with no incoherent noise) from velocity models with a variety of overburden characteristics and run finite-difference simulations over them. Variograms are generated from the synthetic data and show similar trends to those observed in real seismic data. We demonstrate that the length of the coherent signal of a target reflector (derived from the variogram) is directly related to the size and position in depth of the heterogeneity.

In marine geophysics it is difficult to acquire very short offsets due to a number of operational constraints. This is a widely recognised problem in shallow water because SRME needs the near offset primary reflections to predict the free surface multiples. However, given the data with multiples measured at the available offsets, we can derive a multichannel prediction filter which is an excellent approximation of the sea-bed reflector and any other reflectors included in the design. The filter is designed by minimizing the energy in the output of a prediction error process, in a somewhat analogous manner to predictive deconvolution. By use of the focal transform, it is constrained to be composed of a sparse set of hyperbolic functions based upon the wave equation. Given this filter, we may proceed to predict the multiples and remove them as part of an adaptive subtraction scheme.

In marine geophysics it is difficult to acquire very short offsets due to a number of operational constraints. This is a widely recognised problem in shallow water because SRME needs the near offset primary reflections to predict the free surface multiples. However, given the data with multiples measured at the available offsets, we can derive a multichannel prediction filter which is an excellent approximation of the sea-bed reflector and any other reflectors included in the design. The filter is designed by minimizing the energy in the output of a prediction error process, in a somewhat analogous manner to predictive deconvolution. By use of the focal transform, it is constrained to be composed of a sparse set of hyperbolic functions based upon the wave equation. Given this filter, we may proceed to predict the multiples and remove them as part of an adaptive subtraction scheme.

In marine geophysics it is difficult to acquire very short offsets due to a number of operational constraints. This is a widely recognised problem in shallow water because SRME needs the near offset primary reflections to predict the free surface multiples. However, given the data with multiples measured at the available offsets, we can derive a multichannel prediction filter which is an excellent approximation of the sea-bed reflector and any other reflectors included in the design. The filter is designed by minimizing the energy in the output of a prediction error process, in a somewhat analogous manner to predictive deconvolution. By use of the focal transform, it is constrained to be composed of a sparse set of hyperbolic functions based upon the wave equation. Given this filter, we may proceed to predict the multiples and remove them as part of an adaptive subtraction scheme.

Blended or simultaneous sources have been the focus of a good deal of interest recently. In conventional acquisition the time intervals between successive sources are large enough to avoid interference in time. In blended acquisition, temporal overlap between source responses is allowed. The procedure of retrieving data as if they were acquired in the conventional way is called deblending. This is an essential step if standard processing flows are to be applied. Several inversion techniques have been proposed for solving this ill‐posed problem. We study the properties of an iterative estimation and subtraction algorithm that integrates a coherency‐pass filter in a dedicated iteration. We begin by stating the problem we wish to solve and develop a new, more general, interpretation of the method. We then apply an algebraic analysis of the iteration to establish the convergence characteristics of the algorithm. In order to facilitate this analysis, the notion of leakage subspace is introduced, i.e., a subspace where energy that cannot be uniquely assigned to one of the sources resides. We find that a unique solution exists, if, and only if, there is no leakage subspace. If a unique solution does not exist, then the iteration converges to a least‐norm solution contaminated by the projection of the initial guess onto the leakage subspace. The insights gained by this analysis lead us to the development of a simple tool that can provide valuable information during the design of a blended survey. Finally we present results from the application of this method to real blended marine data and then draw our conclusions.

Seismic resolution of towed marine-streamer data is affected by free-surface reflections. They strongly modulate the spectrum reducing energy at the so-called notch frequencies, fn = iv/2z {i = 0,1,…,∞}, in which v is the water velocity and z is the source or receiver depth. As a result there is a very strong loss of useful low-frequency energy and usually a similar loss at higher frequencies. The ghost effect occurs both at the source and at the receiver. At the source, the upgoing part of the source wavefield is reflected off the free surface with inverted polarity before its delayed journey into the Earth. At the receiver, the upgoing part of the receiver wavefield is reflected off the free surface with inverted polarity before it travels down to the receiver again. The over/under acquisition method allows separation of the up- and downgoing wavefields at the source (or receiver) using a vertical pair of sources (or receivers) to determine wave direction. In this article, we present the results of two ...

Many prospective passive ocean margins are covered by large areas of basalts. These basalts are often extremely heterogeneous and scatter the seismic energy of the conventional seismic reflection system so that it becomes difficult to obtain information on deeper reflectors. Since high frequencies are scattered more than low frequencies, we argue that the acquisition system for sub-basalt targets should be modified to emphasize the low frequencies, using much larger airguns, and towing the source and receivers at about 20 m depth. In the summer of 2001 we obtained seismic reflection data over basalt in the northeast Atlantic using a system modified to enhance the low-frequency energy. These new data show deep reflections that are not visible on lines shot in the same places with a conventional system.

Abstract We present a case study from the North West Shelf of Australia where the complexity of the overburden consists of several thin multi-level channel systems filled with a combination of anomalously high or low velocity sediments. Not accounting for these strong velocity variations accurately, can lead to subtle image distortions affecting the underlying section down to and including the reservoir level. This can have significant impact on the volumetric estimates of reserves in place. To resolve these complexities in the overburden, full waveform inversion (FWI) was utilized to generate an updated earth model exploiting both early arrivals and reflection events. One caveat to using full waveform inversion is the need for low frequencies to be present in the seismic data, or, the initial starting velocity model must contain the correct low wavenumber components. However, conventional seismic data acquired at shallow tow depths are usually band limited particularly at the very low frequencies. Our case study will discuss these issues along with other limitations that this "conventional data" presented along with the workflows and quality control methods adapted to this data in order to converge to a plausible, high resolution earth model. Introduction An accurate earth model is fundamental to any depth imaging project. Full waveform inversion is an advanced model building technique incorporating the full two way wave equation. Full waveform inversion produces an accurate high resolution earth model by simultaneously using the information of travel time, amplitude and phase contained in the full recorded seismic wavefield. One pre-requisite to full waveform inversion is an initial starting model. In this case study, the initial starting model was derived from a smooth version of a reflection travel time tomography velocity field derived from a depth migration workflow. The full waveform inversion process utilizes this model and a two-way wave equation finite difference acoustic wavefield propagator to generate modelled seismic data. These modelled shots are then compared to the acquired (observed) recorded seismic shots. The residual differences are backward propagated from time to depth domain, into velocity gradients and velocity changes required to obtain an updated model (see Figure 1). As with solving any non-linear inversion problem, it is an iterative process and is repeated as required until the residuals between the modelled shots and the actual observed seismic data are minimized. Iterations start at low frequencies and progress to higher frequencies.

Summary A workflow for integrating full waveform inversion (FWI) with reflection tomography has been refined using narrow azimuth towed streamer (NATS) 3D seismic data from the North West Shelf (NWS) of Australia. We show that FWI using relatively short offset NATS data with limited low frequency content can provide a high resolution velocity field if it is combined with reflection tomography in the workflow. Although other techniques exist for building an initial FWI model, reflection tomography was chosen here since a reasonably mature model was accessible from a project being run in parallel. Integration of reflection tomography and associated quality control (QC) practices into the frequency domain FWI model building sequence was found to be necessary to help the FWI converge to a satisfactory solution when turning ray energy was limited or non-existent. Investigation of typical FWI parameters was also necessary to refine each frequency update.

Far-field designature is a standard step in the marine processing sequence which converts the source far-field signature to a desired output. The conversion is made by convolving the data by the derived shaping filter. Usually a filter is derived to combine the operations of debubbling and zero-phasing. This approach leaves the source ghost notch in the spectrum of the data and produces a tight zero phase wavelet. The far-field signature is often derived using modeling software (e.g., Nucleus (PGS Seres AS) or Gundalf (Oakwood computing associates Ltd)).

The effects of source and receiver motion on seismic data are considered using extensions of the standard convolutional model. In particular, receiver motion introduces a time-variant spatial shift into data, while source motion converts the effect of the source signature from a single-channel convolution in time to a multichannel convolution in time and space. These results are consistent with classical Doppler theory and suggest that Doppler shifting can introduce distortions into seismic data even at relatively slow acquisition speeds. It is shown that, while both source and receiver motion are known to be important for marine vibroseis acquisition, receiver motion alone can produce significant artifacts in marine 3D data. Fortunately, the convolutional nature of the distortions renders them amenable to correction using simple deconvolution techniques. Specifically, the effects of receiver motion can be neutralized by applying an appropriate reverse time-variant spatial shift, while those due to source motion can be addressed by introducing time-variant spatial shifts both before and after standard, deterministic, signature deconvolution or correlation.

So-called blended or simultaneous source techniques are interesting because they offer the potential for better acquisition sampling, improved illumination and greatly enhanced computational efficiency. The procedure of retrieving data as if they were acquired in the conventional way is called deblending. Several inversion techniques have been proposed for solving this ill-posed problem with the iterative estimation and subtraction algorithm being one of them. This particular method uses a dedicated iteration that integrates a coherency-pass filter. However, fundamental questions regarding the convergence and limitations of this method have not previously been addressed. The notion of the leakage subspace is hereby introduced to aid in this quest.

We appreciate the interest that Saha et al. have shown in our paper and thank them for their prompt response to our request for specific details of their numerical experiments. Our interpretation of these details is given in Appendix A.

The term “simultaneous source” refers to the idea of firing several seismic sources so that their combined energy is recorded into the same set of receivers during a single conventional shotpoint timing cycle. The idea is to collect the equivalent of two or more shots worth of data in the same time as it takes to collect one. The potential advantages include cost or time savings in field acquisition, which is of renewed interest due to the popularity and expense of WATS data. We were motivated to the work presented here by observations made on a 3D dataset acquired over the Petronius field in the Gulf of Mexico with two source vessels. The second source was fired with a random delay compared to the first, so that the energy from secondary source is similar to asynchronous noise. While the random nature of the crosstalk in combination with the two known geometries had been enough to successfully apply relatively standard processing techniques for other studied datasets, we found that this one required an improvement on those techniques. This paper describes a high-resolution (sparse) Radonbased separation technique with that aim. We find that while the technique does not by itself do all the required separation, it sufficiently separates the data to allow subsequent standard noise attenuation techniques to complete the task.

The acquisition of n-shots, more or less simultaneously, increases acquisition efficiency and collects a wider range of information for imaging and reservoir characterisation. Its success relies critically on the ability to separate n-shots from one recording. Stefani et al (2007) showed that while some datasets may be easily separated, others are more difficult. Using the more difficult data example from Stefani et al (loc.cit.), we show that a PEF-based adaptive subtraction (Spitz, 2007) of the estimated wavefield due to a secondary source provides an effective separation of the sources.

In this paper we give a new solution to the problem of factoring p′(t) = a(t) * b(−t) * δ(t−τ) into its maximum‐phase, minimum‐phase, and pure‐delay components. Our method is based on the “winding number” and the solution of three Toeplitz systems of equations. First we use the winding number from complex analysis to estimate the pure‐delay component, which we subsequently remove using p(t)=p′(t)*δ(t+τ). Then we solve the symmetrical Toeplitz system of equations, considering only t ⩾ 0, p(t)*p(-t)*[a(t)*b(t)]-1=a(-t)*b(-t) to get [a(t)*b(t)]-1. Finally, we similarly solve the two asymmetrical Toeplitz systems of equations, p(-t)*[a(t)*b(t)]-1*a(t)=a(-t) for a(t) and p(t)*[a(t)*b(t)]-1*b(t)=b(-t) for b(t). The practical effectiveness of the method is confirmed by application to a synthetic waveform and to an air‐gun signature. When stabilization of the Toeplitz solution is required, we find that it is important to be frugal with the addition of white noise. The computation of the winding number is robust.

Figure 1: Basalt covered areas of the North-East Atlantic Margin and associated igneous centres. Penetrating boreholes and hydrocarbon discoveries near the Shetlands are also shown. Following the findings that one has to use low frequency data to image beneath a multi-layered basalt sequence (Mack, 1997), Veritas DGC and Texaco UK re-shot a profile in August 2001 using a solid streamer and an additional low-frequency setting (Ziolkowski et al., 2001). Comparing the new low-frequency data with the old data shows not only a superior data quality due to the solid streamer used but also improved low-frequency response from beneath the basalt.

The purpose of this work is to help understand the effects of 3D spatial sampling on the quality of the CMP stack in the presence of coherent noise.

Abstract Traditionally seismic spatial sampling has been restricted by operational constraints. Typically shot sampling has been poorer than receiver sampling, yielding non-optimum stacking geometry and aliased contaminated data. Recent advances inthe understanding of the effects of sampling in seismic data and the introduction of techniques that allow interpolationbeyond aliasing, have permitted the pseudo-creation of optimum geometry or 'stack array' from non-optimum acquisition geometry. Two examples are used to show how careful handling of aliased energy and stacking geometry can yield apparently successful results from non-optimum sampled data. The first example is taken from a deep water environment NW of Britain. Data were acquired with a flip-flop source yielding a sub-surface shot interval four times greater than the group interval. In addition the poor sampling intervals lead to the recording of severe spatially aliased water bottom multiples. Application of a spatial antialias filter within the common shot domain followed by interpolation beyond aliasing in the common receiver domain, provides significant improvements to the stack. In the second example, a 2D site survey vessel was used to acquire a high resolution 3D survey with a shot interval equal to half the group interval. However, the larger than desired group interval passed aliased energy. A combination of interpolation beyond aliasing and spatial antialias filtering applied to both shot and receiver domains permitted theunwrapping and removal of aliased energy. The difference between stacks with and without re-sampling is striking. Introduction Seismic surveys are usually acquired with a compromise between theory and finance. Often we design surveys that at least adequately sample in time, but inadequately sample in space. In particular the high costs and limitations on source generation lead to shot sampling that is poorer than receiver sampling, yielding non-optimum stacking geometry and aliased contaminated data. Aliasing is an inherent property of all sampling systems and its effects can be found in a number of seismic processing domains and ultimately in the stack. The consequences of poor spatial sampling were recognized by Anstey1 in his paper 'What ever happened to ground roll?'. More recently authors such as Vermeer2 and Hampson3 have provided further advances in the understanding of spatial sampling theory, particularly in the two dimensional wavenumber domain. A number of processing strategies that overcome the effects of poor field sampling have been suggested,. including pre-stack interpolation (Spitz4, Jakubowicz5) and post-stack wave number notch filtering (Hampson3). This paper intends to demonstrate that a combination of these processing techniques can lead to successful results. Sampling Geometry Optimum symmetrical sampling defined by Vermeer2, is rarely adopted in modem marine 3D acquisition. More commonly, flip-flop source geometries lead to poorer asymmetricalsampling.

In this paper we propose a novel method of acquiring marine seismic data in which screw noise is used as the seismic source. This approach has many potential advantages and might be suitable for seismic acquisition beneath the ice-cap in polar regions .