References

• Cole, S., Claerbout, J.F., Nichols, D., and Zhang, L., 1989, The ambient seismic field in three dimensions: Presented at the 59th Ann. Int'l. Mtg., Soc. Expl. Geophys.

• Nikolaev, A.V., and Troitskiy, P.A., 1987, Lithospheric studies based on array analysis of P-coda and microseisms: Tectonophysics 140, 103-113.

• Vanyan, L., and Cole, S., 1990, Comparison of different approaches to processing ambient noise data: SEP-65, 191-208.

 

l1
Figure 6 Semblance computed along moveout trajectories for possible source locations in 3-D. Each panel corresponds to a different depth. The limits of each picture are the boundaries of the array. Data in the low-frequency range (10-60 Hz) were used, and not surprisingly noise from pumps on the surface dominates the results.

 

gl1 Figure 7 Maximum value of semblance from Figure 6 as a function of depth. Verifies that surface sources dominate.

 

l2
Figure 8 Same semblance computation in 3-D as Figure 6, but for record 2. Surface noise sources dominate again.

 

gl2 Figure 9 Maximum value of semblance vs. depth for Figure 8. Surface sources are not as dominant as in record 1.

 

h1
Figure 10 Semblance computation in 3-D for record 1, using the high frequency range (40-120 Hz) over which pump noise is less dominant. Unlike the low-frequency case (Figure 6), here there are large semblance values at depth.

 

gh1 Figure 11 Maximum value of semblance as a function of depth for Figure 10. Note the increase at around 700 meters, suggesting that non-surface sources are present.

 

h2
Figure 12 Same semblance computation as Figure 10, but for record 2.

 

gh2 Figure 13 Maximum value of semblance vs. depth for Figure 12. Here also there is a semblance increase at depth.