Experimental confirmation of "Reflections on Q"

Laurence R. Lines, Carl Sondergeld, Kristopher A. Innanen, Joe Wong, Sven Treitel, Tadeusz Ulrych

While seismic reflection amplitudes are generally dominated by acoustical impedance contrasts, there is recent interest in reflections due to contrasts in seismic absorption coefficients (or inverse-Q values). In this note, we compare the anelastic reflection coefficient computations with laboratory measurements for such reflections, showing laboratory measurements of reflections at boundaries where there is virtually no contrast in the real part of seismic impedance (product of density and seismic velocity) but where there is a significant contrast in Q. The experiments performed independently by Carl Sondergeld and Joe Wong show reflections from a water/Crisco boundary (where there is Q contrast but no real impedance contrast) that are similar in amplitude but phase-shifted compared to a water/aluminum boundary (where is a large contrast in the real part of seismic impedance). The Sondergeld results are shown in Figure 1 below and the Wong results are shown in an accompanying CREWES report. It is gratifying that both sets of experiments have verified the existence of Q-contrast reflections. However, the Q-contrast reflections are larger than our theories predict and we are revisiting the viscoelastic theories.