High magnitude global seismicity and lateral velocity gradients

1970 ◽  
Vol 80 (1) ◽  
pp. 92-101
Author(s):  
Harsh K. Gupta ◽  
Janardan G. Negi
Keyword(s):  
Lateral Velocity ◽  
Velocity Gradients ◽  
High Magnitude ◽  
Global Seismicity

Reply to Peter Hubral by the Author

Geophysics ◽  
1978 ◽  
Vol 43 (5) ◽  
pp. 1024-1025
Author(s):  
Paul Michaels
Keyword(s):  
Velocity Gradient ◽  
Horizontal Velocity ◽  
Lateral Velocity ◽  
Velocity Gradients ◽  
Coordinate Rotation

Peter Hubral’s extension of the raypath migration calculator program to include a lateral velocity gradient is quite ingenious. In such cases where the vertical and horizontal velocity gradients are constant, the net effect is a simple coordinate rotation. The theoretical raypath remains circular, but is only rotated about its intersection with the datum plane.

Plate tectonics and lateral velocity gradients

1973 ◽  
Vol 16 (3-4) ◽  
pp. 145-154
Author(s):  
Harsh K. Gupta
Keyword(s):  
Plate Tectonics ◽  
Lateral Velocity ◽  
Velocity Gradients

Lateral variation of rayleigh-wave dispersion characteristics in Australia

1970 ◽  
Vol 60 (6) ◽  
pp. 1897-1906
Author(s):  
Harsh K. Gupta ◽  
Janardan G. Negi
Keyword(s):  
Rayleigh Wave ◽  
Wave Dispersion ◽  
Dispersion Characteristics ◽  
Lateral Variation ◽  
Lateral Velocity ◽  
Entire Family ◽  
Period Range ◽  
Velocity Gradients ◽  
Dispersion Data ◽  
Rayleigh Wave Dispersion

Abstract Rayleigh wave dispersion data on Australia by Bolt and Niazi (1964) and Thomas (1969) are examined in detail in the period range of 20 to 40 sec. The dispersion characteristics correspond well to region 7 in Santô's (1965) classification. A further and similar inspection of the African mass, Brazilian shield, Canadian shield etc. reveals that the entire family of shield areas systematically belongs to Santô's regions 6 and/or 7. They are uniformly characterized by the absence of appreciable lateral velocity gradients in clear contrast to corresponding extremely steep gradients for high seismicity areas.

Wave‐equation migration in the presence of lateral velocity variations

Geophysics ◽  
1982 ◽  
Vol 47 (7) ◽  
pp. 1001-1011 ◽  
Author(s):  
Richard Jay Castle
Keyword(s):  
Wave Equation ◽  
Three Dimensional ◽  
Scalar Wave ◽  
Lateral Velocity ◽  
Scalar Wave Equation ◽  
Common Depth Point ◽  
Velocity Gradients ◽  
Velocity Variations ◽  
Integral Solutions ◽  
Dimensional Wave

An algorithm for three‐dimensional wave equation migration in the presence of lateral velocity gradients is developed. The algorithm is based geophysically on the exploding reflector model and mathematically on integral solutions to the scalar wave equation. In addition, the velocity is assumed to vary slowly over a seismic wavelength. The primary application of the algorithm is to stacked sections. However, if the velocity is a function of depth only, the algorithm may be used to migrate and/or image common‐depth‐point gathers.

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