Some problems in velocity analysis for marine deep seismic profiles

McBride, John H.; Lindsey, G.; Hobbs, Richard; Snyder, David B.; Totterdell, I.

doi:10.3997/1365-2397.1993018

Cited by 11 publications

(5 citation statements)

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“…Stacking velocities used throughout the processing were picked using semblance, mini-stack panels, and trial midpoint gathers (e.g., McBride et al, 1993) to maximize the coherency of primary reflections. These stacking velocities were kept consistent with coincident interval velocity models estimated from refracted seismic P-wave arrivals recorded on the streamer, ocean bottom seismometers, and landstations (Brittan et al, this volume; Christeson et al, this volume).…”

Section: Seismic Data Processingmentioning

confidence: 99%

Deep seismic reflection profiles across the Chicxulub Crater

Snyder¹,

Hobbs²

1999

Large Meteorite Impacts and Planetary Evolution; II

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The deep seismic reflection profiles acquired during the British Institutions Reflection Profiling Syndicate (BIRPS) survey off the north coast of Yucatán, during September-October 1996, have clarified the geometries of several major features of the Chicxulub impact structure. The most prominent reflectors observed on each of the four radial profiles are related to a Jurassic-Cretaceous stratum at 2-3-km depths and to the Moho at 30-35-km depths. The prominent Mesozoic reflector provides a key marker of near-surface deformation within the preimpact strata at depths great enough to avoid immediate erosion after the impact, and it indicates three major "rings" of impact-related deformation to the upper crust. Prominent reflectors within the lower crust are generally continuous for 1-10 km. The Moho reflectors indicate, in conjunction with the velocity models, variations of only a few kilometers in the thickness of crust beneath the crater. Several crustal reflectors project upward at dips of ca. 30° from Moho depths to the primary deformation zones defined by disruptions to the prominent Mesozoic reflector, suggesting that these reflectors represent shear zones whose reflectivity was enhanced by the rapid injection of impact melt.

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Section: Seismic Data Processingmentioning

confidence: 99%

Deep seismic reflection profiles across the Chicxulub Crater

Snyder¹,

Hobbs²

1999

Large Meteorite Impacts and Planetary Evolution; II

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“…for arrivals with zero-offset traveltimes of 10 to 15 s TWT at offsets where the normal moveout approximation is still valid (McBride et al 1993;Dahl-Jensen et al 1995), although with decreasing fold and signal-to-noise ratio this may drop to rt400 m s-' (Law 1993).…”

Section: T H E B a B E L Pre-critical W I D E -A N G L E D A T Amentioning

confidence: 99%

Determination of Poisson's ratio from pre-critical wide-angle seismic reflection data from the BABEL project

Law¹,

Snyder²,

Singh³

1995

Geophysical Journal International

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S U M M A R YThe pre-critical wide-angle seismic reflection data collected during the BABEL survey using multireceiver spreads contain high-amplitude P-wave and modeconverted S-wave reflected arrivals. The two phases can be partially separated and their signal-to-noise ratio emphasized by exploiting the multifold nature and the increased sensitivity of velocity analysis afforded by these data to produce zero-offset-corrected stacked sections. Using these sections, a method has been developed to derive estimates of Poisson's ratio by optimizing the cross-correlation of P-wave and S-wave arrivals, and hence to constrain petrological models of the crust sampled by these data. Although the apparently high degree of temporal and spatial resolution of reflected arrivals that are visible within the stacked sections must be reduced to achieve a satisfactory degree of correlation robustness, the results shed some light on crustal petrology, and concur with existing estimates of Poisson's ratio for the Baltic shield.

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“…These offsets provide good velocity resolution on the uppermost few kilometres of sediment in typical sedimentary basin settings, but little velocity information at greater depths (McBride et al 1993). Single-ship seismic surveys have used offsets governed by the length of the streamer: in the 1960s this was generally 2.4 km, increasing steadily through the years until 6 km is the norm at present for single-ship surveys, and under special circumstances up to 12 km streamers have been deployed.…”

Section: Introductionmentioning

confidence: 99%

“…Single-ship seismic surveys have used offsets governed by the length of the streamer: in the 1960s this was generally 2.4 km, increasing steadily through the years until 6 km is the norm at present for single-ship surveys, and under special circumstances up to 12 km streamers have been deployed. These offsets provide good velocity resolution on the uppermost few kilometres of sediment in typical sedimentary basin settings, but little velocity information at greater depths (McBride et al 1993).…”

Section: Introductionmentioning

confidence: 99%

A comparison between airguns and explosives as wide‐angle seismic sources

Staples

Hobbs²,

White

1999

Geophysical Prospecting

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The relative merits of a 48‐gun, 9324 cu. in. (153 litre) airgun array and a 200 kg explosive source are considered for the purposes of long‐range (0–400 km) refraction seismic work, with particular reference to traveltime modelling. Theoretical source calculations indicate that in the frequency range 2.5–12.0 Hz, the airgun source will produce an RMS pressure ∼ 8% of that produced by the explosive source and an initial burst pressure ∼17% of that produced by the explosive source. Observed data support these calculations at short ranges and illustrate the greater attenuation of the airgun signal with range due to its lack of very low frequency (< 5 Hz) content. At short offsets, the airgun array provides a preferable seismic source to the explosives, due to densely spaced shots and a consistent waveform resulting in excellent trace‐to‐trace coherence. With increasing offsets, it may be necessary to stack the airgun data to enhance its signal‐to‐noise ratio: here we use a 4‐fold stack. Large explosive shots, although more powerful, produce a less consistent waveform and are more widely spaced due to operational constraints. The offset at which airguns provide a preferable source is dependent on the ambient noise. This practical comparison of real sources demonstrates that, even without advanced processing, a well‐tuned airgun array may provide a preferable source to explosives at offsets up to 160 km, under favourable experimental conditions.

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Some problems in velocity analysis for marine deep seismic profiles

Cited by 11 publications

References 0 publications

Deep seismic reflection profiles across the Chicxulub Crater

Deep seismic reflection profiles across the Chicxulub Crater

Determination of Poisson's ratio from pre-critical wide-angle seismic reflection data from the BABEL project

A comparison between airguns and explosives as wide‐angle seismic sources

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