Imaging refractors with the convolution section

Palmer, Derecke

doi:10.1190/1.1487103

Cited by 50 publications

(45 citation statements)

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“…This study describes two approaches to full waveform refraction seismology, using common offset gathers (COG) (Palmer, 2010c(Palmer, , 2013 and the refraction convolution section (RCS) (Palmer, 2001a). These methods are applied to the first break refraction data which were acquired as part of regional seismic reflection investigations, over part of the Palaeozoic Lachlan Fold Belt in south-eastern Australia (Barton and Jones, 2003).…”

Section: Introductionmentioning

confidence: 99%

Is It Time To Modernize Near-Surface Refraction Seismology With Full Waveform Methods?

Palmer

2015

ASEG Extended Abstracts

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Section: Introductionmentioning

confidence: 99%

Is It Time To Modernize Near-Surface Refraction Seismology With Full Waveform Methods?

Palmer

2015

ASEG Extended Abstracts

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“…of Palmer (2001aPalmer ( , 2001bPalmer ( , 2001c. How this method is used to estimate relative physical layer properties is also discussed.…”

Section: Thesis Methodology and Outlinementioning

confidence: 99%

“…Palmer, 2000Palmer, , 2001aPalmer, , 2001bPalmer, , 2001c. In these papers, the offset dependence is removed by convolving forward and reverse shot records.…”

Section: Previous Head-wave Amplitude Studiesmentioning

confidence: 99%

“…In these papers, the offset dependence is removed by convolving forward and reverse shot records. It is suggested that the amplitude of the resulting refraction convolution section (RCS) is proportional to the head-wave coefficient (Palmer, 2001b). The RCS is then used to estimate lateral changes in physical properties, specifically seismic velocity.…”

Section: Previous Head-wave Amplitude Studiesmentioning

confidence: 99%

“…Whiteley (2011) One process that does attempt to derive relative layer velocity information from refraction amplitudes is called the refraction convolution section (RCS) (Palmer, 2001a(Palmer, , 2001b(Palmer, , 2001c.…”

Section: Previous Head-wave Amplitude Studiesmentioning

confidence: 99%

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Inversion of seismic refraction amplitudes for near-surface velocity control

Meulenbroek¹

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Analysis of seismic refraction amplitudes has the potential to produce a richer geological interpretation than if only travel-times are considered. In theory, the amplitude of a seismic head-wave is dependent on the strength of the shot and the offset at which it is measured. A constant of proportionality, called the head-wave coefficient, is a function of the elastic properties either side of the refracting interface. As the velocity contrast between the two media decreases, the head-wave coefficient increases.A detailed examination of refraction amplitude theory reveals that the head-wave coefficient is a product of two Zoeppritz transmission coefficients, a downgoing one at the source end and an upgoing one at the receiver end. The bulk amplitude of the head-wave coefficient is mainly due to the transmission coefficient at the receiver end. However, the receiver component is relatively insensitive to lateral changes. On the other hand, the transmission coefficient at the source end is sensitive to lateral changes.Theoretical models, which simulate laterally inhomogeneous geologies, are used to forwardmodel refraction amplitudes. The head-wave coefficient is then estimated via non-linear inversion of refraction amplitudes. Inverted shot and receiver terms are shown to be related to the transmission coefficients at the shot and receiver ends. The product of the inverted shot and receiver terms are related to the full head-wave coefficient. The inversion cannot separate the effect of velocity contrast from short-wavelength shot/geophone coupling effects. Smoothing of the inverted solution is suggested as a means of reducing coupling effects.For laterally inhomogeneous models, offset limiting is required prior to inversion in order to achieve successful separation of constituent amplitude components. For offset-limited model data, the estimated model parameters exhibit consistency with the true model parameters in a relative sense.iii Non-uniqueness between parameter groups prohibits successful estimation of model parameters in an absolute sense. Calibration is therefore required to adjust the relative results obtained from inversion to results which are consistent with geology. This calibration uses independent estimates of weathering-layer velocity at several points along the seismic line.Calibration can be performed on the inverted shot terms alone, or the product of the inverted shot and receiver terms.The inversion methodology is evaluated on three real data sets. For the first Vibroseis dataset, the relative head-wave coefficient profile is consistent with that derived using an alternative approach (the Refraction Convolution Section). However, the implied weathering-layer velocity profile differs from that estimated by analysis of direct arrivals.For the second Vibroseis dataset, the derived weathering-layer velocity is reasonably consistent with the long-wavelength velocity profile derived from analysis of hammer shot records, acquired as part of the original survey. The CMP stack, incorporating t...

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Seismic Methods

Schuck¹,

Lange²

2007

Environmental Geology

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Imaging refractors with the convolution section

Cited by 50 publications

References 12 publications

Is It Time To Modernize Near-Surface Refraction Seismology With Full Waveform Methods?

Is It Time To Modernize Near-Surface Refraction Seismology With Full Waveform Methods?

Inversion of seismic refraction amplitudes for near-surface velocity control

Seismic Methods

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