Source radiation patterns for S-wave exploration

2017 ◽  
Author(s):  
James Gaiser
Keyword(s):  
Radiation Patterns ◽  
S Wave ◽  
Source Radiation

Borehole seismic‐source radiation pattern in transversely isotropic media

Geophysics ◽  
1995 ◽  
Vol 60 (1) ◽  
pp. 29-42 ◽  
Author(s):  
Wenjie Dong ◽  
M. Nafi Toksöz
Keyword(s):  
Radiation Effects ◽  
Low Frequency ◽  
Transversely Isotropic ◽  
Seismic Source ◽  
Wave Pattern ◽  
Radiation Patterns ◽  
S Wave ◽  
Source Radiation ◽  
Air Gun ◽  
Borehole Seismic

We extend previous discussions on crosswell tomography in anisotropic formations by deriving the radiation patterns of three typical downhole seismic sources (impulsive air gun or dynamite, wall‐clamped vertical vibrators, and cylindrical bender) inside a fluid‐filled borehole embedded in a transversely isotropic (TI) formation. The method of steepest descents, in conjuncture with the low‐frequency and far‐field assumptions, is applied to the exact displacement integrals of these sources to obtain their radiation patterns asymptotically. In spite of complications caused by quasi‐P‐ and quasi‐SV‐wave coupling and wavefront triplication in homogeneous TI media, the final results can still be expressed in slowness components determined by a ray direction, which is desired when source radiation effects are to be accounted for by ray‐based tomography techniques. Tests with the radiation patterns show that while the effect of anisotropy on P‐waves is moderate, its effect on the S‐wave pattern is significant even for slightly anisotropic formations. One can predict the S‐wave pattern from the sign of the Thomsen’s measure δ*.

Seismic point-source radiation patterns

2021 ◽  
pp. 463-484
Author(s):  
Charles J. Ammon ◽  
Aaron A. Velasco ◽  
Thorne Lay ◽  
Terry C. Wallace
Keyword(s):  
Point Source ◽  
Radiation Patterns ◽  
Source Radiation

scholarly journals Elastic orthorhombic anisotropic parameter inversion: An analysis of parameterization

Geophysics ◽  
2016 ◽  
Vol 81 (6) ◽  
pp. C279-C293 ◽  
Author(s):  
Ju-Won Oh ◽  
Tariq Alkhalifah
Keyword(s):  
Wave Velocity ◽  
Dimensionless Parameter ◽  
P Wave ◽  
Radiation Patterns ◽  
S Wave ◽  
Velocity Perturbation ◽  
Anisotropic Parameter ◽  
P Wave Velocity ◽  
Parameter Perturbations ◽  
Scattering Potential

The resolution of a multiparameter full-waveform inversion (FWI) is highly influenced by the parameterization used in the inversion algorithm, as well as the data quality and the sensitivity of the data to the elastic parameters because the scattering patterns of the partial derivative wavefields (PDWs) vary with parameterization. For this reason, it is important to identify an optimal parameterization for elastic orthorhombic FWI by analyzing the radiation patterns of the PDWs for many reasonable model parameterizations. We have promoted a parameterization that allows for the separation of the anisotropic properties in the radiation patterns. The central parameter of this parameterization is the horizontal P-wave velocity, with an isotropic scattering potential, influencing the data at all scales and directions. This parameterization decouples the influence of the scattering potential given by the P-wave velocity perturbation from the polar changes described by two dimensionless parameter perturbations and from the azimuthal variation given by three additional dimensionless parameters perturbations. In addition, the scattering potentials of the P-wave velocity perturbation are also decoupled from the elastic influences given by one S-wave velocity and two additional dimensionless parameter perturbations. The vertical S-wave velocity is chosen with the best resolution obtained from S-wave reflections and converted waves, and little influence on P-waves in conventional surface seismic acquisition. The influence of the density on observed data can be absorbed by one anisotropic parameter that has a similar radiation pattern. The additional seven dimensionless parameters describe the polar and azimuth variations in the P- and S-waves that we may acquire, with some of the parameters having distinct influences on the recorded data on the earth’s surface. These characteristics of the new parameterization offer the potential for a multistage inversion from high symmetry anisotropy to lower symmetry ones.

Radiation patterns: Possibility for monitoring seismic sources

Geophysics ◽  
1996 ◽  
Vol 61 (1) ◽  
pp. 282-287
Author(s):  
Philip Carrion ◽  
José Carcione ◽  
Edson E. S. Sampaio
Keyword(s):  
Point Source ◽  
Field Measurements ◽  
Seismic Sources ◽  
Seismic Events ◽  
Elastic Media ◽  
Radiation Patterns ◽  
Source Radiation ◽  
Earth Environment ◽  
Source Excitation ◽  
Homogeneous Media

Recent field measurements of the radiation in boreholes indicate that the radiation patterns of real seismic sources are not always in agreement with those corresponding to the point‐source excitation in unbounded homogeneous and isotropic acoustic or elastic media [we refer the reader to Aki and Richards (1980) for the basic discussion on the radiation patterns in homogeneous media]. This mismatch results from the fact that the point‐source radiation patterns corresponding to homogeneous media are too simplistic to satisfy any experiment in the more realistic Earth environment. A study of radiation patterns is certainly important not only to predict possible seismic events but also to analyze the source performance itself by recording seismic arrivals.

RADIATION OF BODY WAVES FROM NEAR‐SURFACE EXPLOSIVE SOURCES

Geophysics ◽  
1966 ◽  
Vol 31 (6) ◽  
pp. 1057-1065 ◽  
Author(s):  
I. N. Gupta ◽  
C. Kisslinger
Keyword(s):  
Free Surface ◽  
Body Waves ◽  
Radiation Patterns ◽  
S Wave ◽  
Near Surface ◽  
S Waves ◽  
Nuclear Explosions ◽  
Plexiglas Sheet ◽  
Chemical Explosions ◽  
Seismic Models

Amplitude distributions obtained from field observations of the azimuthal distribution of motion from cratering shots near a vertical face in a limestone section yielded data on radiation into a half‐space. These effects have been approximately reproduced in the laboratory by means of two‐dimensional seismic models. Small chemical explosions were fired on or near the edge of a large plexiglas sheet and the radiation of both P and S waves observed. Shots on the edge of the model sheet produce P and S radiation patterns expected from a normal downward impulse on the free surface. The radiation patterns from cratering shots may be qualitatively explained by the combined action on the free surface of a normal downward stress and a pair of horizontal stresses (dipole without moment) at the source point. The observed data are not sufficient for verifying theoretical S wave distributions. Observations of SV amplitudes from nuclear explosions could yield useful information concerning the relation between the angle at which the waves leave the source and the distance at which the wave emerges.

Average body-wave radiation coefficients

1984 ◽  
Vol 74 (5) ◽  
pp. 1615-1621
Author(s):  
David M. Boore ◽  
John Boatwright
Keyword(s):  
High Frequency ◽  
Body Wave ◽  
Strike Slip ◽  
Wave Radiation ◽  
Radiation Patterns ◽  
S Wave ◽  
P Waves ◽  
Effective Radiation ◽  
Average Body

Abstract Averages of P- and S-wave radiation patterns over all azimuths and various ranges of takeoff angles (corresponding to observations at teleseismic, regional, and near distances) have been computed for use in seismological applications requiring average radiation coefficients. Various fault orientations and averages of the squared, absolute, and logarithmic radiation patterns have been considered. Effective radiation patterns combining high-frequency direct and surfacere-flected waves from shallow faults have also been derived and used in the computation of average radiation coefficients at teleseismic distances. In most cases, the radiation coefficients are within a factor of 1.6 of the commonly used values of 0.52 and 0.63 for the rms of P- and S-wave radiation patterns, respectively, averaged over the whole focal sphere. The main exceptions to this conclusion are the coefficients for P waves at teleseismic distances from vertical strike-slip faults, which are at least a factor of 2.8 smaller than the commonly used value.

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