Surface-wave-based inversions of shallow seismic structure

Larson, Gregg D.; Alam, M. Shahria; Martin, James S.; Scott, Waymond R.; McClellan, J.H.; McCall, George S.; Norville, Pelham D.; Declety, Benjamin

doi:10.1117/12.487474

Cited by 6 publications

(3 citation statements)

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“…The effects of the prograde wave are diminished in the approximated gradient measurements because the prograde wave propagates faster than the Rayleigh wave in the experimental model. 11 The subsonic prograde wave ͑at approximately 180 m / s͒ produces an evanescent acoustic field in the air that decays more slowly with distance from the surface than the signal associated with the Rayleigh wave. Prograde waves have been measured as fast as 460 m / s at field test sites.…”

Section: Sensitivity Improvementsmentioning

confidence: 99%

“…Prograde waves have been measured as fast as 460 m / s at field test sites. 11 These would generate propagating air-acoustic signals with predominantly horizontal velocities that could be discriminated against by a measurement of the vertical pressure gradient.…”

Section: Sensitivity Improvementsmentioning

confidence: 99%

“…These are the lowest order P-SV ͑coupled pressure and vertical shear wave͒ mode that is guided by the interface between a vertically heterogeneous medium and the overlying air. In soil, over the frequency range of interest, these waves typically propagate at speeds between 70 and 160 m / s. 11,12 For the measurements reported here, Rayleigh wave speeds were measured at approximately 80 m / s. Because they are subsonic, soil-borne Rayleigh waves produce evanescent acoustic fields in the air above the soil. Below 2 kHz, these signals have been measured with microphones up to 10 cm above the air-soil interface.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Investigation of microphones as near-ground sensors for seismic detection of buried landmines

Larson

Martin

Scott

2007

The Journal of the Acoustical Society of America

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Commercially available microphones were investigated as near-ground sensors to measure the acoustic pressure and the vertical pressure gradient of evanescent air-acoustic waves associated with audio-frequency seismic waves. Measurements in close proximity to the surface and the use of waveguides were found to improve the microphone signal's quality, the comparison of its seismic sensitivity to its sensitivity to propagating sound (ambient acoustic noise and nonseismic reverberation). Landmine images formed using microphone data collected in a laboratory experimental model clearly locate buried inert landmines but exhibit more clutter than images of the same objects formed with seismic displacement data collected using other techniques.

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Section: Sensitivity Improvementsmentioning

confidence: 99%

Section: Sensitivity Improvementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Investigation of microphones as near-ground sensors for seismic detection of buried landmines

Larson

Martin

Scott

2007

The Journal of the Acoustical Society of America

Self Cite

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Passive detection of buried structures using elastic waves

Norville

Scott

2003

SPIE Proceedings

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An investigation of the feasibility of detecting structures buried underground through passive listening techniques will be presented. Passive detection of structures will be analyzed using elastic wave sources originating inside the structure and from sources exterior to the structure and on the surface. The primary method of investigation will be numerical models using the finite-difference time-domain method (FDTD).A source inside the structure excites elastic waves in the structure, a portion of which travel upward along the walls of the structure and onward to the surface. An alternate form of excitation is a source such as a train, large vehicle, or an explosion located on the surface, away from the structure. Waves from this source interact with the structure and a portion of them travel up from the structure to the surface.An array of sensors is constructed to map the field at the surface and to determine the location and basic characteristics of the structure. Generally, structures examined will be on the order of the size of an underground tunnel complex or buried room and elastic wave sources will be in the low frequency range of large machinery or vehicles.

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