ERSC 3V93 Lecture Notes - Lecture 45: Seismic Refraction, Acoustic Impedance, Seismic Wave
4 May 2016
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Document Summary
For v2 > v1 there is a critical angle at which the incident ray is refracted along the interface with refr = 90 critically refracted wave called a head wave" basis of seismic refraction method. Plugging in 90 for the angle of refraction we get: Still get refracted p and s wave but no headwave. V1 < v2 ray refracted at angle greater than angle of incidence angles of reflection remain the same for v1 > v2 ray refracted at angle less than angle of incidence. At angles of incidence beyond critical all energy is reflected back to surface no headwaves or refracted waves. Seismic reflection method - record two- way travel times of reflections. Seismic refraction method - record travel times of critically refracted" waves. Proportions of energy reflected and transmitted are determined by the contrast in the acoustic impedance z. Measure of medium"s ability to transmit sound waves.
