Velocity Gradients in the Continental Crust from Head-Wave Amplitudes
CALIFORNIA INST OF TECH PASADENA SEISMOLOGICAL LAB
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Small velocity gradients in a refracting horizon have a pronounced effect on the spectral amplitudes of head waves. Negative velocity gradients and anelasticity Q sup -1 result in a similar amplitude decay with distance for narrow-bandwidth data. Positive velocity gradients result in a net amplitude gain with distance compared with the head wave from a homogeneous, perfectly elastic refractor. Wave-theoretical expressions for these effects applied to published amplitude data for the major crustal refraction branches.