Field comparison of shallow seismic sources

Miller, Richard D.; Pullan, Susan E.; Waldner, Jeffrey S.; Haeni, F.P.

doi:10.1190/1.1442061

Cited by 119 publications

(67 citation statements)

References 2 publications

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“…The wavelets shown in comparisons (Miller et al, 1986) of typical near-surface sources result in two dominant peaks for individual reflections from an interface in which a larger acoustic impedance is encountered, depending somewhat upon display parameters. Conversely, shallow seismic sources typically produce only one dominant peak per reflector when the signal is reflected from an interface characterized by a material having a smaller acoustic impedance.…”

Section: Data Interpretation Pitfallsmentioning

confidence: 99%

Avoiding pitfalls in shallow seismic reflection surveys

1998

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Acquiring shallow reflection data requires the use of high frequencies, preferably accompanied by broad bandwidths. Problems that sometimes arise with this type of seismic information include spatial aliasing of ground roll, erroneous interpretation of processed airwaves and air-coupled waves as reflected seismic waves, misinterpretation of refractions as reflections on stacked common-midpoint (CMP) sections, and emergence of processing artifacts. Processing and interpreting nearsurface reflection data correctly often requires more than a simple scaling-down of the methods used in oil and gas exploration or crustal studies. For example, even under favorable conditions, separating shallow reflections from shallow refractions during processing may prove difficult, if not impossible. Artifacts emanating from inadequate velocity analysis and inaccurate static corrections during processing are at least as troublesome when they emerge on shallow reflection sections as they are on sections typical of petroleum exploration. Consequently, when using shallow seismic reflection, an interpreter must be exceptionally careful not to misinterpret as reflections those many coherent waves that may appear to be reflections but are not. Evaluating the validity of a processed, shallow seismic reflection section therefore requires that the interpreter have access to at least one field record and, ideally, to copies of one or more of the intermediate processing steps to corroborate the interpretation and to monitor for artifacts introduced by digital processing.

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Section: Data Interpretation Pitfallsmentioning

confidence: 99%

Avoiding pitfalls in shallow seismic reflection surveys

1998

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“…Thus, an ideal source does not exist, and the "best" source at one site may not be the best source at the same site under different moisture or soil-compaction conditions or at another site. Several papers discuss source comparisons for SSR data collected at various sites (e.g., Miller et al, 1986Miller et al, , 1992Miller et al, , 1994) and a single site under different soil-moisture conditions and on different days (Baker et al, 1997;Jefferson et al, 1998).…”

Section: Discussionmentioning

confidence: 99%

Source-Dependent Frequency Content of Ultrashallow Seismic Reflection Data

Baker

Steeples

Schmeissner

et al. 2000

Bulletin of the Seismological Society of America

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Seismic surveying within the upper few meters of the Earth's shallow subsurface requires a high-frequency source. To ascertain the important features of such sources, experiments were conducted at test sites in central and eastern Kansas using various impulsive seismic sources (4.5-kg hammer, 30.06 rifle, and .22-caliber rifle) to examine the effects of minimizing source energy on the frequency content of reflection data. Results indicate that the higher energy near-surface seismicreflection sources (e.g., sledgehammer, large-caliber projectiles) lack some of the high-frequency energy exhibited by smaller sources, precluding the detection of reflection signal from ultrashallow depths (Ͻ3 m) at the sites tested. At the test site in eastern Kansas, the .22-caliber rifle yielded more energy above 250 Hz than either the sledgehammer or 30.06 rifle. At the test site in central Kansas, where three reflective interfaces shallower than 3 m exist, the .22-caliber rifle with subsonic ammunition yielded the largest amount of energy at frequencies above 300 Hz and produced the best data.

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“…A Betsy seisgun (Miller et al, 1986) firing 8-gauge lead slugs was used as the seismic source. A consistent minimum sourceto-receiver offset of 1.8 m (6 ft) was maintained during each test.…”

Section: Methodsmentioning

confidence: 99%

Effects of soil‐moisture content on shallow‐seismic data

et al. 1998

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Repeated shallow-seismic experiments were conducted at a site on days with different near-surface moisture conditions in unconsolidated material. Experimental field parameters remained constant to ensure comparability of results. Variations in the seismic data are attributed to the changes in soil-moisture content of the unconsolidated material. Higher amplitudes of reflections and refractions were obtained under wetter near-surface conditions. An increase in amplitude of 21 dB in the 100-300 Hz frequency range was observed when the moisture content increased from 18% to 36% in the upper 0.15 m (0.5 ft) of the subsurface. In the timedomain records, highly saturated soil conditions caused large-amplitude ringy wavelets that interfered with and degraded the appearance of some of the reflection information in the raw field data. This may indicate that an intermediate near-surface moisture content is most conducive to the recording of high-quality shallow-seismic reflection data at this site. This study illustrates the drastic changes that can occur in shallow-seismic data due to variations in near-surface moisture conditions. These conditions may need to be considered to optimize the acquisition timing and parameters prior to collection of data.

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Field comparison of shallow seismic sources

Cited by 119 publications

References 2 publications

Avoiding pitfalls in shallow seismic reflection surveys

Avoiding pitfalls in shallow seismic reflection surveys

Source-Dependent Frequency Content of Ultrashallow Seismic Reflection Data

Effects of soil‐moisture content on shallow‐seismic data

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