Broadside interferometric and reverse‐time imaging of the San Andreas Fault at depth

Vasconcelos, Ivan; Taylor, Stewart; Snieder, Roel; Chavarria, J. Andres; Sava, Paul; Malin, Péter

doi:10.1190/1.2792918

Cited by 4 publications

(2 citation statements)

References 16 publications

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“…We argue ͑see also Vasconcelos et al, 2007͒ that this reflector coincides with the SAF's contact with metamorphic rocks to the northeast. Events indicated by red arrows 1 and 4 in Fig …”

Section: S136mentioning

confidence: 93%

Interferometry by deconvolution: Part 2 — Theory for elastic waves and application to drill-bit seismic imaging

2008

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Deconvolution interferometry successfully recovers the impulse response between two receivers without the need for an independent estimate of the source function. Here we extend the method of interferometry by deconvolution to multicomponent data in elastic media.As in the acoustic case, elastic deconvolution interferometry retrieves only causal scattered waves that propagate between two receivers as if one acts as a pseudosource of the point-force type. Interferometry by deconvolution in elastic media also generates artifacts because of a clamped-point boundary condition imposed by the deconvolution process. In seismic-while-drilling ͑SWD͒ practice, the goal is to determine the subsurface impulse response from drill-bit noise records. Most SWD technologies rely on pilot sensors and/or models to predict the drill-bit source function, whose imprint is then removed from the data. Interferometry by deconvolution is of most use to SWD applications in which pilot records are absent or provide unreliable estimates of bit excitation. With a numerical SWD subsalt example, we show that deconvolution interferometry provides an image of the subsurface that cannot be obtained by correlations without an estimate of the source autocorrelation. Finally, we test the use of deconvolution interferometry in processing SWD field data acquired at the San Andreas Fault Observatory at Depth ͑SAFOD͒. Because no pilot records were available for these data, deconvolution outperforms correlation in obtaining an interferometric image of the San Andreas fault zone at depth.

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“…We argue ͑see also Vasconcelos et al, 2007͒ that this reflector coincides with the SAF's contact with metamorphic rocks to the northeast. Events indicated by red arrows 1 and 4 in Fig …”

Section: S136mentioning

confidence: 93%

Interferometry by deconvolution: Part 2 — Theory for elastic waves and application to drill-bit seismic imaging

2008

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“…Calvert ͑2004, 2006͒ use their virtualsource method to image beneath a complex overburden from borehole sensors in a horizontal well with no knowledge of the overburden model parameters. Vasconcelos and Snieder ͑2008a;2008b͒ andVasconcelos et al ͑2007͒ use drill-bit noise recordings with a deconvolution interferometry method to perform broadside imaging of the San Andreas Fault at Parkfield, California. In the context of saltflank imaging, Willis et al ͑2006͒ present a numerical example that demonstrates that diving waves can be used for interferometric imaging of near-vertical salt reflectors.…”

Section: Introductionmentioning

confidence: 99%

Imaging internal multiples from subsalt VSP data — Examples of target-oriented interferometry

2008

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Seismic interferometry has become a technology of growing interest for imaging borehole seismic data. We demonstrate that interferometry of internal multiples can be used to image targets above a borehole receiver array. By internal multiples, we refer to all types of waves that scatter multiple times inside the model. These include, for instance, interbed, intrasalt, and water-bottom multiples as well as conversions among them. We use an interferometry technique that is based on representation theorems for perturbed media and targets the reconstruction of specific primary reflections from multiply reflected waves. In this interferometry approach, we rely on shot-domain wavenumber separation to select the directions of waves arriving at a given receiver. Using a numerical walkaway ͑WAW͒ VSP experiment recorded by a subsalt borehole receiver array in the Sigsbee salt model, we use the interference of internal multiples to image the salt structure from below. In this numerical example, the interferometric image that uses internal multiples reconstructs the bottomand top-of-salt reflectors above the receiver array as well as the subsalt sediment structure between the array and the salt. Because of the limited source summation in this interferometry example, the interferometric images show artifact reflectors within the salt body. We apply this method to a field walkaway VSP from the Gulf of Mexico. With the field data, we demonstrate that the choice of shot-domain wavenumbers in the target-oriented interferometry procedure controls the wavenumbers in the output pseudoshot gathers. Target-oriented interferometric imaging from the 20-receiver array recovers the top-of-salt reflector that is consistent with surface seismic images. We present our results with both correlationbased and deconvolution-based interferometry.

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Interferometry by deconvolution: Part 1 — Theory for acoustic waves and numerical examples

2008

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Interferometry allows for synthesis of data recorded at any two receivers into waves that propagate between these receivers as if one of them behaves as a source. This is accomplished typically by crosscorrelations. Based on perturbation theory and representation theorems, we show that interferometry also can be done by deconvolutions for arbitrary media and multidimensional experiments. This is important for interferometry applications in which ͑1͒ excitation is a complicated source-time function and/or ͑2͒ when wavefield separation methods are used along with interferometry to retrieve specific arrivals. Unlike using crosscorrelations, this method yields only causal scattered waves that propagate between the receivers. We offer a physical interpretation of deconvolution interferometry based on scattering theory. Here we show that deconvolution interferometry in acoustic media imposes an extra boundary condition, which we refer to as the free-point or clamped-point boundary condition, depending on the measured field quantity. This boundary condition generates so-called free-point scattering interactions, which are described in detail. The extra boundary condition and its associated artifacts can be circumvented by separating the reference waves from scattered wavefields prior to interferometry. Three wavefield-separation methods that can be used in interferometry are direct-wave interferometry, dual-field interferometry, and shot-domain separation. Each has different objectives and requirements.

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Broadside interferometric and reverse‐time imaging of the San Andreas Fault at depth

Cited by 4 publications

References 16 publications

Interferometry by deconvolution: Part 2 — Theory for elastic waves and application to drill-bit seismic imaging

Interferometry by deconvolution: Part 2 — Theory for elastic waves and application to drill-bit seismic imaging

Imaging internal multiples from subsalt VSP data — Examples of target-oriented interferometry

Interferometry by deconvolution: Part 1 — Theory for acoustic waves and numerical examples

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