SHEAR WAVES FROM EXPLOSIVE SOURCES

Geophysics ◽  
1963 ◽  
Vol 28 (6) ◽  
pp. 1001-1019 ◽  
Author(s):  
J. E. White ◽  
R. L. Sengbush
Keyword(s):  
Shear Waves ◽  
Shear Velocity ◽  
Compressional Waves ◽  
Pierre Shale ◽  
Strong Shear ◽  
Water Pulse ◽  
Pulse Waves ◽  
Tube Wave ◽  
A Charge ◽  
Shear Energy

This experimental study of the generation of shear waves by explosive sources stemmed from Heelan’s theoretical result that pressure acting on the wall of a cylindrical hole in a solid should radiate shear waves quite as effectively as compressional waves. The measurements confirm this expectation, but good overall agreement was not achieved until expressions were derived which take into account radiation from strong water‐pulse waves in the shothole. Our results show that the ratio of shear‐to‐compressional amplitudes generated by an explosive source increases as the charge size decreases. At an angle of 45 degrees, the ratio is approximately unity for a charge consisting of 10 ft of Primacord. We found that the shot‐generated water pulse (tube wave) is a strong shear source, continuously generating shear energy in the formation as it travels in the borehole. This drastically affects the directivity of SV waves and in Pierre shale gives a pattern whose maximum is near‐vertical. This suggests the possibility of prospecting with shear waves, using a distributed charge detonated at shear velocity to generate substantial downward‐direction shear energy in the earth. However, the substantially larger attenuation of shear waves compared to compressional waves has discouraged us from pursuing this further.

Delineating a cased borehole in unconsolidated formations using dipole acoustic data from a nearby well

Geophysics ◽  
2021 ◽  
pp. 1-39
Author(s):  
Gu Xihao ◽  
Xiao-Ming Tang ◽  
Yuan-Da Su
Keyword(s):  
Shear Waves ◽  
Low Frequency ◽  
Well Being ◽  
Compressional Wave ◽  
Acoustic Imaging ◽  
Wave Radiation ◽  
Dipole Source ◽  
Compressional Waves ◽  
Single Well ◽  
Cased Borehole

A potential application for single-well acoustic imaging is the detection of an existing cased borehole in the vicinity of the well being drilled, which is important for drilling toward (when drilling a relief well), or away from (collision prevention), the existing borehole. To fulfill this application in the unconsolidated formation of shallow sediments, we propose a detection method using the low-frequency compressional waves from dipole acoustic logging. For this application, we perform theoretical analyses on elastic wave scattering from the cased borehole and derive the analytical expressions for the scattered wavefield for the incidence of compressional and shear waves from a borehole dipole source. The analytical solution, in conjunction with the elastic reciprocity theorem, provides a fast algorithm for modeling the whole process of wave radiation, scattering, and reception for the borehole acoustic detection problem. The analytical results agree well with those from 3D finite-difference simulations. The results show that compressional waves, instead of shear waves as commonly used for dipole acoustic imaging, are particularly advantageous for the borehole detection in the unconsolidated formation. Field data examples are used to demonstrate the application in a shallow marine environment, where dipole-compressional wave data in the measurement well successfully delineate a nearby cased borehole, validating our analysis results and application.

Assessing the Effects of Near Wall Corrections of the Force Acting on Particles in Gas-Solid Channel Flows

2005 ◽  
Author(s):  
Boris Arcen ◽  
Anne Tanie`re ◽  
Benoiˆt Oesterle´
Keyword(s):  
Channel Flow ◽  
Lift Force ◽  
Particle Concentration ◽  
Turbulent Channel Flow ◽  
Shear Velocity ◽  
Solid Particles ◽  
Wall Region ◽  
Wall Effects ◽  
Strong Shear ◽  
Near Wall

The importance of using the lift force and wall-corrections of the drag coefficient for modeling the motion of solid particles in a fully-developed channel flow is investigated by means of direct numerical simulation (DNS). The turbulent channel flow is computed at a Reynolds number based on the wall-shear velocity and channel half-width of 185. Contrary to most of the numerical simulations, we consider in the present study a lift force formulation that accounts for the weak and strong shear as well as for the wall effects (hereinafter referred to as optimum lift force), and the wall-corrections of the drag force. The DNS results show that the optimum lift force and the wall-corrections of the drag together have little influence on most of the statistics (particle concentration, mean velocities, and mean relative and drift velocities), even in the near wall region.

THE USE OF SEISMIC SHEAR WAVES AND COMPRESSIONAL WAVES FOR LITHOLOGICAL PROBLEMS OF SHALLOW SEDIMENTS*

1984 ◽  
Vol 32 (4) ◽  
pp. 662-675 ◽  
Author(s):  
H. STUMPEL ◽  
S. KAHLER ◽  
R. MEISSNER ◽  
B. MILKEREIT
Keyword(s):  
Shear Waves ◽  
Compressional Waves ◽  
Seismic Shear ◽  
Shallow Sediments

ATTENUATION OF SHEAR AND COMPRESSIONAL WAVES IN PIERRE SHALE

Geophysics ◽  
1958 ◽  
Vol 23 (3) ◽  
pp. 421-439 ◽  
Author(s):  
F. J. McDonal ◽  
F. A. Angona ◽  
R. L. Mills ◽  
R. L. Sengbush ◽  
R. G. Van Nostrand ◽  
...  
Keyword(s):  
Band System ◽  
Vertical Motion ◽  
Wide Band ◽  
Wave Form ◽  
Frequency Content ◽  
Frequency Range ◽  
Compressional Waves ◽  
Pierre Shale ◽  
Velocity Wave ◽  
Wave Forms

Attenuation measurements were made near Limon, Colorado, where the Pierre shale is unusually uniform from depths of less than 100 ft to approximately 4,000 ft. Particle velocity wave forms were measured at distances up to 750 ft from explosive and mechanical sources. Explosives gave a well‐defined compressional pulse which was observed along vertical and horizontal travel paths. A weight dropped on the bottom of a borehole gave a horizontally‐traveling shear wave with vertical particle motion. In each case, signals from three‐component clusters of geophones rigidly clamped in boreholes were amplified by a calibrated, wide‐band system and recorded oscillographically. The frequency content of each wave form was obtained by Fourier analysis, and attenuation as a function of frequency was computed from these spectra. For vertically‐traveling compressional waves, an average of 6 determinations over the frequency range of 50–450 cps gives α=0.12 f. For horizontally‐traveling shear waves with vertical motion in the frequency range 20–125 cps, the results are expressed by α=1.0 f. In each case attenuation is expressed in decibels per 1,000 ft of travel and f is frequency in cps. These measurements indicate, therefore, that the Pierre shale does not behave as a visco‐elastic material.

scholarly journals Shear wave imaging from traffic noise using seismic interferometry by cross-coherence

Geophysics ◽  
2011 ◽  
Vol 76 (6) ◽  
pp. SA97-SA106 ◽  
Author(s):  
Norimitsu Nakata ◽  
Roel Snieder ◽  
Takeshi Tsuji ◽  
Ken Larner ◽  
Toshifumi Matsuoka
Keyword(s):  
Surface Waves ◽  
Traffic Noise ◽  
Random Noise ◽  
Shear Waves ◽  
Shear Velocity ◽  
Body Waves ◽  
Seismic Interferometry ◽  
Spectral Amplitude ◽  
Interval Velocity ◽  
Wide Range

We apply the cross-coherence method to the seismic interferometry of traffic noise, which originates from roads and railways, to retrieve both body waves and surface-waves. Our preferred algorithm in the presence of highly variable and strong additive random noise uses cross-coherence, which uses normalization by the spectral amplitude of each of the traces, rather than crosscorrelation or deconvolution. This normalization suppresses the influence of additive noise and overcomes problems resulting from amplitude variations among input traces. By using only the phase information and ignoring amplitude information, the method effectively removes the source signature from the extracted response and yields a stable structural reconstruction even in the presence of strong noise. This algorithm is particularly effective where the relative amplitude among the original traces is highly variable from trace to trace. We use the extracted, reflected shear waves from the traffic noise data to construct a stacked and migrated image, and we use the extracted surface-waves (Love waves) to estimate the shear velocity as a function of depth. This profile agrees well with the interval velocity obtained from the normal moveout of the reflected shear waves constructed by seismic interferometry. These results are useful in a wide range of situations applicable to both geophysics and civil engineering.

Virtual shear source makes shear waves with air guns

Geophysics ◽  
2007 ◽  
Vol 72 (2) ◽  
pp. A7-A11 ◽  
Author(s):  
Andrey Bakulin ◽  
Albena Mateeva ◽  
Rodney Calvert ◽  
Patsy Jorgensen ◽  
Jorge Lopez
Keyword(s):  
Shear Wave ◽  
Shear Waves ◽  
Shear Velocity ◽  
Velocity Profiles ◽  
Virtual Source ◽  
S Wave ◽  
Converted Wave ◽  
Source Method ◽  
Vsp Data ◽  
Walkaway Vsp

We demonstrate a novel application of the virtual source method to create shear-wave sources at the location of buried geophones. These virtual downhole sources excite shear waves with a different radiation pattern than known sources. They can be useful in various shear-wave applications. Here we focus on the virtual shear check shot to generate accurate shear-velocity profiles in offshore environments using typical acquisition for marine walkaway vertical seismic profiling (VSP). The virtual source method is applied to walkaway VSP data to obtain new traces resembling seismograms acquired with downhole seismic sources at geophone locations, thus bypassing any overburden complexity. The virtual sources can be synthesized to radiate predominantly shear waves by collecting converted-wave energy scattered throughout the overburden. We illustrate the concept in a synthetic layered model and demonstrate the method by estimating accurate P- and S-wave velocity profiles below salt using a walkaway VSP from the deepwater Gulf of Mexico.

Sonic to ultrasonic Q of sandstones and limestones: Laboratory measurements at in situ pressures

Geophysics ◽  
2009 ◽  
Vol 74 (2) ◽  
pp. WA93-WA101 ◽  
Author(s):  
Clive McCann ◽  
Jeremy Sothcott
Keyword(s):  
Wave Attenuation ◽  
Shear Waves ◽  
Compressional Wave ◽  
Ultrasonic Frequency ◽  
Laboratory Measurements ◽  
Compressional Waves ◽  
Wave Velocities ◽  
Poisson's Ratios ◽  
Poisson’S Ratios

Laboratory measurements of the attenuation and velocity dispersion of compressional and shear waves at appropriate frequencies, pressures, and temperatures can aid interpretation of seismic and well-log surveys as well as indicate absorption mechanisms in rocks. Construction and calibration of resonant-bar equipment was used to measure velocities and attenuations of standing shear and extensional waves in copper-jacketed right cylinders of rocks ([Formula: see text] in length, [Formula: see text] in diameter) in the sonic frequency range and at differential pressures up to [Formula: see text]. We also measured ultrasonic velocities and attenuations of compressional and shear waves in [Formula: see text]-diameter samples of the rocks at identical pressures. Extensional-mode velocities determined from the resonant bar are systematically too low, yielding unreliable Poisson’s ratios. Poisson’s ratios determined from the ultrasonic data are frequency corrected and used to calculate thesonic-frequency compressional-wave velocities and attenuations from the shear- and extensional-mode data. We calculate the bulk-modulus loss. The accuracies of attenuation data (expressed as [Formula: see text], where [Formula: see text] is the quality factor) are [Formula: see text] for compressional and shear waves at ultrasonic frequency, [Formula: see text] for shear waves, and [Formula: see text] for compressional waves at sonic frequency. Example sonic-frequency data show that the energy absorption in a limestone is small ([Formula: see text] greater than 200 and stress independent) and is primarily due to poroelasticity, whereas that in the two sandstones is variable in magnitude ([Formula: see text] ranges from less than 50 to greater than 300, at reservoir pressures) and arises from a combination of poroelasticity and viscoelasticity. A graph of compressional-wave attenuation versus compressional-wave velocity at reservoir pressures differentiates high-permeability ([Formula: see text], [Formula: see text]) brine-saturated sandstones from low-permeability ([Formula: see text], [Formula: see text]) sandstones and shales.

Converted shear waves as seen by ocean bottom seismometers and surface buoys

1977 ◽  
Vol 67 (5) ◽  
pp. 1291-1302 ◽  
Author(s):  
Brian T. R. Lewis ◽  
James McClain
Keyword(s):  
Shear Waves ◽  
Shear Velocity ◽  
Ocean Bottom ◽  
Sediment Layer ◽  
S Waves ◽  
High Attenuation ◽  
Ocean Bottom Seismometers ◽  
Sedimentary Layer ◽  
Low Shear

abstract It is found that ocean bottom seismometers (O.B.S.) deployed in sedimented areas produce markedly different seismograms from surface hydrophones. These differences are found to be due to ringing on the O.B.S. records produced by converted shear waves trapped in the sediment layer. These shear waves do not propagate into the water and hence the hydrophone record is much “cleaner” than the O.B.S. record. It is also shown that the presence of refracted shear waves like P-S-P and P-S-S may be related to the presence of a sedimentary layer in some areas. It is suggested that the disappearance of refracted S waves in some areas without sediment is related to high attenuation and/or very low shear velocities caused by cracks and inhomogeneities in the crust. Under sedimented areas the cracks may be sufficiently filled so as to substantially reduce the attenuation and/or increase the bulk shear velocity.

A multiscale study of the mechanisms controlling shear velocity anisotropy in the San Andreas Fault Observatory at Depth

Geophysics ◽  
2006 ◽  
Vol 71 (5) ◽  
pp. F131-F146 ◽  
Author(s):  
Naomi L. Boness ◽  
Mark D. Zoback
Keyword(s):  
Seismic Anisotropy ◽  
San Andreas Fault ◽  
Shear Waves ◽  
Shear Velocity ◽  
Granitic Rocks ◽  
Velocity Anisotropy ◽  
Bedding Planes ◽  
San Andreas ◽  
State Of Stress ◽  
Sonic Logs

We present an analysis of shear velocity anisotropy using data in and near the San Andreas Fault Observatory at Depth (SAFOD) to investigate the physical mechanisms controlling velocity anisotropy and the effects of frequency and scale. We analyze data from borehole dipole sonic logs and present the results from a shear-wave-splitting analysis performed on waveforms from microearthquakes recorded on a downhole seismic array. We show how seismic anisotropy is linked either to structures such as sedimentary bedding planes or to the state of stress, depending on the physical properties of the formation. For an arbitrarily oriented wellbore, we model the apparent fast direction that is measured with dipole sonic logs if the shear waves are polarized by arbitrarily dipping transversely isotropic (TI) structural planes (bedding/fractures). Our results indicate that the contemporary state of stress is the dominant mechanism governing shear velocity anisotropy in both highly fractured granitic rocks and well-bedded arkosic sandstones. In contrast, within the finely laminated shales, anisotropy is a result of the structural alignment of clays along the sedimentary bedding planes. By analyzing shear velocity anisotropy at sonic wavelengths over scales of meters and at seismic frequencies over scales of several kilometers, we show that the polarization of the shear waves and the amount of anisotropy recorded are strongly dependent on the frequency and scale of investigation. The shear anisotropy data provide constraints on the orientation of the maximum horizontal compressive stress [Formula: see text] and suggest that, at a distance of only [Formula: see text] from the San Andreas fault (SAF), [Formula: see text] is at an angle of approximately 70° to the strike of the fault. This observation is consistent with the hypothesis that the SAF is a weak fault slipping at low levels of shear stress.

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