L12_WavesAndRays-page7 - Therefore high frequencies decay...

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Applied Geophysics – Waves and rays - I Attenuation The amplitude of an arrival decreases with distance from the source 1. Geometric spreading Energy spread over a sphere: 4 µ r 2 Amplitude 1/r 2. Intrinsic attenuation Rocks are not perfectly elastic. Some energy is lost as heat due to frictional dissipation. Amplitude e - α r where α is the absorption coefficient (dependent on wavelength) Total attenuation A= (A 0 e - α r )/r Higher frequencies attenuate over shorter distances due to their shorter wavelengths.
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Unformatted text preview: Therefore, high frequencies decay first leaving a low frequency signal remaining. Applied Geophysics – Waves and rays - I Reflection and transmission Seismic rays obey Snell’s Law (just like in optics) The angle of incidence equals the angle of reflection, and the angle of transmission is related to the angle of incidence through the velocity ratio. 2 1 1 sin sin sin P P P P P P V r V R V i = =...
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This note was uploaded on 01/07/2012 for the course PHYSICS 384 taught by Professor Wei during the Spring '09 term at SUNY Stony Brook.

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