Continuous Analysis of the Velocity Function and of the Move Out Corrections*

Garotta, Robert; Michon, D.

doi:10.1111/j.1365-2478.1967.tb01805.x

Cited by 26 publications

(9 citation statements)

References 0 publications

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“…The CMP recording technique is usually employed to improve the signal-to-noise ratio with redundant recording during reflection seismic-data acquisition (Garotta and Michon, 1967; Yilmaz, 1987), and has also been applied successfully to GPR surveys (Fisher and others, 1992; Greaves and others, 1996). In addition, multifold coverage with nonzero-offset recording yields velocity information about the subsurface.…”

Section: Data Equipment and Methodsmentioning

confidence: 99%

Electromagnetic wave speed in polar ice: validation of the common-midpoint technique with high-resolution dielectric-profiling and γ-density measurements

et al. 2002

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The accuracy of the travel-time–velocity and travel-time–depth profile derived from ground-penetrating radar (GPR) common-midpoint (CMP) surveys at different frequencies is investigated for the first time ever by direct comparison with the profile calculated from high-resolution dielectric-profiling (DEP) ice-core data. In addition, we compare two travel-time profiles calculated from ice-core density data by means of different dielectrical mixture models with the DEP-based profile. CMP surveys were carried out at frequencies of 25,50,100 and 200 MHz near the new European deep-drilling site DML05 in Dronning Maud Land, Antarctica, during the 1998/99 field season. An improved scanning capacitor for high-resolution DEP and a γ-densiometer for density measurements were used to determine the complex dielectric constant and the density at 5 mm increments along the ice core B32, retrieved in 1997/98 at DML05. The comparisons with DEP- and density-based velocity series show that the CMP velocity series are slightly higher but asymptotically approach the core-based velocities with depth. Root-mean-square differences of the DEP velocity series range between 8% for the 25 MHz CMP and 2% in the case of the 200 MHz survey. Density-based velocities differ from the DEP velocities by 51 %. The travel-time–depth series calculated from the interval velocities show a better agreement between all series than the velocity series. Differences are 5.7–1.4% for the 25 and 200 MHz CMP measurements, and <0.6% for the density data. Based on these comparisons, we evaluate the accuracy with which the depth of electromagnetic reflectors observed in common-offset profiles can be determined, and discuss reasons for the observed differences between CMP- and core-based profiles. Moreover, we compare the errors determined from the field measurements with those estimated from GPR system characteristics to provide a measure that can be used to estimate the accuracy of GPR analyses for the planning of GPR campaigns. Our results show that CMP surveys are a useful technique to determine the depth of radar reflectors in combination with common-offset measurements, especially on a region-wide basis.

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Section: Data Equipment and Methodsmentioning

confidence: 99%

Electromagnetic wave speed in polar ice: validation of the common-midpoint technique with high-resolution dielectric-profiling and γ-density measurements

et al. 2002

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“…For the CMP recording technique, the distance between TX and RX is symmetrically increased relative to the stationary centre point, basically yielding information about the wave speed–depth profile. This method is a standard tool in seismic data acquisition (Garotta and Michon, 1967; Yilmaz, 1987), and has also been applied successfully in modified versions to glaciological GPR surveys (Gudmandsen, 1971; Hempel et al, 2000; Murray et al, 2000).…”

Section: Gpr Methodologymentioning

confidence: 99%

Alpine ice cores and ground penetrating radar: combined investigations for glaciological and climatic interpretations of a cold Alpine ice body

Eisen¹,

Nixdorf²,

Keck³

et al. 2003

Tellus B

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Accurate interpretation of ice cores as climate archives requires detailed knowledge of their past and present geophysical environment. Different techniques facilitate the determination and reconstruction of glaciological settings surrounding the drilling location. During the ALPCLIM 1 project, two ice cores containing long-term climate information were retrieved from Colle Gnifetti, Swiss-Italian Alps. Here, we investigate the potential of ground penetrating radar (GPR) surveys, in conjuction with ice core data, to obtain information about the internal structure of the cold Alpine ice body to improve climatic interpretations. Three drill sites are connected by GPR profiles, running parallel and perpendicular to the flow line, thus yielding a three-dimensional picture of the subsurface and enabling the tracking of internal reflection horizons between the locations. As the observed reflections are of isochronic origin, they permit the transfer of age-depth relations between the ice cores. The accuracy of the GPR results is estimated by comparison of transferred timescales with original core datings, independent information from an older ice core, and, based on glaciological surface data, findings from flow modeling. Our study demonstrates that GPR is a mandatory tool for Alpine ice core studies, as it permits mapping of major transitions in physical-chemical properties, transfer of age-depth relations between sites, correlate signals in core records for interpretation, and establish a detailed picture of the flow regime surrounding the climate archive.

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“…Velocity analysis refers to a class of methods of estimating the sound speed through some best-fit data processing approach in which the optimum alignment of echoes is chosen using some index of coherence. [22][23][24][25] To our knowledge, the direct calculation of sound speed from echo data aligned using cross correlation was first proposed and applied by Schneider and Backus. 23 The differences in the signal processing approach used by Schneider and Backus and that described in Sec.…”

Section: Fig 2 ͑Top͒mentioning

confidence: 99%

The direct estimation of sound speed using pulse–echo ultrasound

Anderson

Trahey

1998

The Journal of the Acoustical Society of America

104

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A method for the direct estimation of the longitudinal speed of sound in a medium is presented. This estimator derives the speed of sound through analysis of pulse-echo data received across a single transducer array following a single transmission, and is analogous to methods used in exploration seismology. A potential application of this estimator is the dynamic correction of beamforming errors in medical imaging that result from discrepancy between the assumed and actual biological tissue velocities. The theoretical basis of this estimator is described and its function demonstrated in phantom experiments. Using a wire target, sound-speed estimates in water, methanol, ethanol, and n-butanol are compared to published values. Sound-speed estimates in two speckle-generating phantoms are also compared to expected values. The mean relative errors of these estimates are all less than 0.4%, and under the most ideal experimental conditions are less than 0.1%. The relative errors of estimates based on independent regions of speckle-generating phantoms have a standard deviation on the order of 0.5%. Simulation results showing the relative significance of potential sources of estimate error are presented. The impact of sound-speed errors on imaging and the potential of this estimator for phase aberration correction and tissue characterization are also discussed.

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Continuous Analysis of the Velocity Function and of the Move Out Corrections*

Cited by 26 publications

References 0 publications

Electromagnetic wave speed in polar ice: validation of the common-midpoint technique with high-resolution dielectric-profiling and γ-density measurements

Electromagnetic wave speed in polar ice: validation of the common-midpoint technique with high-resolution dielectric-profiling and γ-density measurements

Alpine ice cores and ground penetrating radar: combined investigations for glaciological and climatic interpretations of a cold Alpine ice body

The direct estimation of sound speed using pulse–echo ultrasound

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