Ray theory and its extensions: WKBJ and Maslov seismograms
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Asymptotic ray theory can be used to describe many seismic signals. Provided the wavefronts and amplitudes vary smoothly and the correct phase changes are included for caustics and reflection/transmission coefficients, it successfully describes direct and turning rays, on normal and reversed branches with multiple turning points, and partial and total reflections and transmissions. Nevertheless, many exceptions occur. Critical points, head waves, interference head waves, Airy caustics, Fresnel shadows, edge, point and interface diffractions and gradient coupling are examples discussed in this paper. Asymptotic ray theory can be simply extended to cover some of these problems. In this paper, the extension called the WKBJ or Maslov seismogram is discussed.
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