1. Interferometric Extraction of SSP from Passive Seismic Data Yanwei Xue Feb. 7, 2008

2. OUTLINE  Motivation  Theory  Field data test  Conclusions and the way ahead

3. Motivation   No individual experiment required   Can get Green’s function between two randomly selected receivers Why? How?   Interferometric Transform

4. OUTLINE  Motivation  Theory  Field data test  Conclusions and the way ahead

5. Random Sources =δ(x-x’)S(ω) =δ(x-x’)S(ω) P(B) = P(B) = ∫ G(B|x)N(x)d x 2 S src Im[G(A|B)] = k Im[G(A|B)] = k = k = k ∫ G(B|x)G(A|x)*d x2 S src A B..S0 S src x x’ z

6. Random Scatterers

7. Workflow Input data d Truncate d in time into several data panels Truncate d in time into several data panels Crosscorrelate each trace with a given trace at x Crosscorrelate each trace with a given trace at x Sum and average the crosscorrelation panels Sum and average the crosscorrelation panels Output

8. OUTLINE  Motivation  Theory  Field data test  Conclusion and the way ahead

9. Data Introduction 8 receiver lines 779 receivers Receiver interval: 27 - 30 m 1 2 3 4 5 6 7 8 6100 0 06100 X (m) Y (m) Receiver position

10. Amplitude Time (s)0960 Trace Example

11. Virtual Shot Gather Receiver line 6 90 receivers Frequency used to do the interferometry is 1 - 11.5 Hz Event velocity 1450 m/s 0.0 2.4 0 2500 Time (s) X (m)

12. 0.0 2.4 0 2500 Time (s) X (m) Receiver line 6 90 receivers Frequency used: 1 – 9 Hz Event velocity 1450 m/s Virtual Shot Gather

13. 0.0 2.4 0 2500 Time (s) X (m) Receiver line 8 95 receivers Frequency used: 1 - 9 Hz Event velocity 1455 m/s

14. 0.0 2.4 0 2500 Time (s) X (m) Virtual Shot Gather Receiver line 2 90 receivers Frequency used: 1 - 5 Hz

15. Receiver line 2 90 receivers Frequency used: 1 - 44 Hz Left-going events removed 0.0 2.4 0 2500 Time (s) X (m) Virtual Shot Gather

16. OUTLINE  Introduction  Theory  Field data test  Conclusions and the way ahead

17. Conclusions  Field data test gives continuous events  Low frequency results have a velocity of 1450 m/s  High frequency (1 - 44 Hz) results look like reflections  We need records with longer time to get better results

18. Road Ahead  Test the data with longer time records  Velocity analysis of the virtual gathers  Migrate the virtual data

19. Thanks!