Reflections on Q

Laurence R. Lines and Fereidoon Vasheghani

ABSTRACT

Seismic reflections are generally caused by contrasts in acoustic impedance. However, in media where there is significant absorption of seismic energy, reflections can also be caused by contrasts in the seismic absorption coefficient (or inverse-Q values). This note derives the reflection coefficient for a normally incident acoustic wave, and then uses seismic modeling of SH-wave reflections for absorptive media using the finite-difference codes of Carcione (2007). As predicted by theory and modeling, there are weak reflections due to contrasts in seismic absorption that show phase differences from reflections caused by impedance contrast.

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