David Halliday

Interferometric surface-wave isolation and removal

Theremovalofsurfacewavesgroundrollfromlandseismicdataiscriticalinseismicprocessingbecausethesewaves tend to mask informative body-wave arrivals. Removal becomes difficult when surface waves are scattered, and data qualityisoftenimpaired.Weapplyamethodofseismicinterferometry, using both sources and receivers at the surface, to estimatethesurface-wavecomponentoftheGreen’sfunction betweenanytwopoints.Theseestimatesaresubtractedadaptively from seismic survey data, providing a new method of ground-roll removal that is not limited to nonscattering regions.

Seismic surface waves in a suburban environment: Active and passive interferometric methods

Seismic interferometry refers to a new range of methods where inter-receiver wavefields (those that would have been recorded if one of each pair of receivers had been a source) can be estimated by cross-correlation of wavefields recorded at each of the receivers. These methods have found many applications in different fields of seismology, including creating “virtual” sources in wells under complex overburdens, computational full-wavefield modelling, and passive construction of surface wave waveforms from background noise in the Earth. Curtis et al. (2006) provide an overview of various applications of seismic interferometry referred to herein, and more in-depth works can be found in the special supplement on Seismic Interferometry in the July-August issue of GEOPHYSICS.

Interferometric ground-roll removal: Attenuation of scattered surface waves in single-sensor data

Land seismic data are contaminated by surface waves (or ground roll). These surface waves are a form of source-generated noise and can be strongly scattered by near-surface heterogeneities. The resulting scattered ground roll can be particularly difficult to separate from the desired reflection data, especially when this scattered ground roll propagates in the crossline direction. We have used seismic interferometry to estimate scattered surface waves, recorded during an exploration seismic survey, between pairs of receiver locations. Where sources and receivers coincide, these interreceiver surface-wave estimates were adaptively subtracted from the data. This predictive-subtraction process can successfully attenuate scattered surface waves while preserving the valuable reflected arrivals, forming a new method of scattered ground-roll attenuation. We refer to this as interferometric ground-roll removal.

An interferometric theory of source-receiver scattering and imaging

It is known that there is a link between the theory of seismic interferometry and theories of seismic imaging and inversion. However, although this has been discussed in several studies, there are few where any explicit links have been derived. We use reciprocity theorems for scattering media to derive a new form of seismic interferometry that describes the scattered wavefield between a source and a receiver in an acoustic medium, using both sources and receivers on two enclosing boundaries. This form of seismic interferometry is equivalent to a generalized imaging condition (IC) that combines the full wavefield inside any finite-sized subregion of the medium of interest. By using the Born (single-scattering) approximation, this generalized IC reduces to the method of imaging by double-focusing originally derived by Michael Oristaglio in 1989. Thus an explicit link is made between seismic interferometry, new generalized full-wavefield ICs, and existing single-scattering imaging methods.

Directional balancing for seismic and general wavefield interferometry

In passive seismic interferometry using naturally occurring, heterogeneous noise sources and in active-source seismic interferometry where sources can usually only be distributed densely on the exterior of solid bodies, bias can be introduced in Green’s function estimates when amplitudes of energy have directional variations. We have developed an algorithm to remove bias in Green’s function estimates constructed using seismic interferometry when amplitudes of energy used have uncontrollable directional variations. The new algorithm consists of two parts:1 a method to measure and adjust the amplitudes of physical, incoming energy using an array of receivers and 2 a method to predict and remove nonphysical energy that remains and can be accentuated in interferometrically derived Green’s functions after applying the method in step 1. To accomplish step 2, we have created two data-driven methods to predict the nonphysical energy using direct computation or move-out-based methods, and a way to suppress such energy usingin this case helical leastsquares filters. Two-dimensional acoustic scattering examples confirm the algorithm’s effectiveness.

Full-wavefield, Towed-marine Seismic Acquisition and Applications

A four-component (4C) streamer recording pressure as well as the three-component particle velocity vector, addresses long-standing geophysical problems such as receiver-side sampling and deghosting. In this paper, we introduce multicomponent marine seismic sources generating monopole and dipole responses in the water. We describe a few different alternatives for generating such a source using existing technology. Three different application areas are described in some detail: source-side deghosting, source-side wavefield reconstruction and, finally, a vector-acoustic reverse-time imaging approach that requires monopole and dipole data on both the source and receiver side of the acquisition.

Source-receiver interferometry for seismic wavefield construction and ground-roll removal

Seismic interferometry describes the construction of unmeasured wavefield responses (or Greens functions) between two or more points by applying cross-correlation, deconvolution, or convolution to seismic data recordings. The practical implications are that, applying inter-receiver interferometry, a “virtual” (imaginary) source of energy can be created at the location to a real receiver by using energy recorded from surrounding sources. Similarly, by using inter-source interferometry, a virtual receiver can be created at the location of a real source by using energy recorded at surrounding receivers (Curtis et al., 2009). These two methods can be combined to create the new technique of source-receiver interferometry (Curtis, 2009; Curtis and Halliday, 2010; Halliday and Curtis, 2010) which synthesizes real-source to real-receiver Greens function estimates using only energy recorded at a surrounding boundary of receivers and from an additional surrounding boundary of sources. The boundary sources in each...

Scattered ground‐roll attenuation using model‐driven interferometry

Scattered ground roll is a type of noise observed in land seismic data that can be particularly difficult to suppress. Typically, this type of noise cannot be removed using conventional velocity-based filters. In this paper, we discuss a model-driven form of seismic interferometry that allows suppression of scattered ground-roll noise in land seismic data. The conventional cross-correlate and stack interferometry approach results in scattered noise estimates between two receiver locations (i.e. as if one of the receivers had been replaced by a source). For noise suppression, this requires that each source we wish to attenuate the noise from is co-located with a receiver. The model-driven form differs, as the use of a simple model in place of one of the inputs for interferometry allows the scattered noise estimate to be made between a source and a receiver. This allows the method to be more flexible, as co-location of sources and receivers is not required, and the method can be applied to data sets with a variety of different acquisition geometries. A simple plane-wave model is used, allowing the method to remain relatively data driven, with weighting factors for the plane waves determined using a least-squares solution. Using a number of both synthetic and real two-dimensional (2D) and three-dimensional (3D) land seismic data sets, we show that this model-driven approach provides effective results, allowing suppression of scattered ground-roll noise without having an adverse effect on the underlying signal.

Adaptive interferometry for ground-roll suppression

Generally, seismic interferometry refers to a method of extracting the wavefield responses between two receivers as if we had replaced one of those receivers by a source (van Manen et al., 2005; Wapenaar and Fokkema, 2006). This is done by a process of cross-correlation and summation of wavefields observed at those receivers. These recorded wavefields can be excited by active sources (earthquakes, dynamite, air guns, vibroseis, and others) or passive sources (oceanic microseisms, traffic on roads, industrial machinery, and others). When applying seismic interferometry using surface sources and surface receivers, the recovered inter-receiver response is dominated by surface waves. This phenomenon is observed in both global and regional seismology where passive seismic energy is used, and in exploration seismology, where active sources are used.

Extracting reflectivity response from point-receiver ambient noise

Summary We introduce a workflow that allows subsurface imaging using the upcoming body-wave arrivals extracted from ambient noise land data. Rather than using the conventional seismic interferometry approach (based on correlation), we propose a specific deconvolution technique to extract the earth response from the observed periodicity in the seismic traces. This technique consists of iteratively applying a gapped spiking deconvolution, providing sharper images, with higher resolution than conventional correlation. Our workflow is validated with simple synthetic data and real data recorded during a small point-receiver land seismic