1. Making CMP’s From chapter 16 “Elements of 3D Seismology” by Chris Liner

2. Outline Normal Moveout Stacking

3. Normal Moveout x T Hyperbola:

4. Normal Moveout x T “Overcorrected” Normal Moveout is too large Chosen velocity for NMO is too (a) large (b) small

5. Normal Moveout x T “Overcorrected” Normal Moveout is too large Chosen velocity for NMO is too small (a) large (b) small

6. Normal Moveout x T “Under corrected” Normal Moveout is too small Chosen velocity for NMO is (a) too large (b) too small

7. Normal Moveout x T “Under corrected” Normal Moveout is too small Chosen velocity for NMO is too large (a) too large (b) too small

8. Vinterval from Vrms Dix, 1955

9. Vrms V1 V2 V3 Vrms < Vinterval

10. Vinterval from Vrms

11. Primary seismic events x T

12. x T

13. x T

14. x T

15. Multiples and Primaries x T M1 M2

16. Conventional NMO before stacking x T NMO correction V=V(depth) e.g., V=mz + B M1 M2 “Properly corrected” Normal Moveout is just right Chosen velocity for NMO is correct

17. Over-correction (e.g. 80% Vnmo) x T NMO correction V=V(depth) e.g., V=0.8(mz + B) M1 M2 x T M1 M2

18. f-k filtering before stacking (Ryu) x T NMO correction V=V(depth) e.g., V=0.8(mz + B) M1 M2 x T

19. Correct back to 100% NMO x T NMO correction V=V(depth) e.g., V=(mz + B) M1 M2 x T M1 M2

20. Outline Convolution and Deconvolution Normal Moveout Stacking

21. NMO stretching V1 V2 T0T0 “NMO Stretching”

22. NMO stretching V1V1 V2V2 T0T0 “NMO Stretching” V 1 <V 2

23. NMO stretching V1V1 V2V2 V 1 <V 2 NMO “stretch” = “linear strain” Linear strain (%) = final length-original length original length X 100 (%)

24. NMO stretching V1V1 V2V2 V 1 <V 2 X 100 (%) original length = final length = NMO “stretch” = X 100 (%)

25. stretching for T=2s,V1=V2=1500 m/s Green line assumes V1=V2 Blue line is for general case, where V1, V2 can be different and delT0=0.1s (this case: V1=V2) Matlab code

26. Stacking + + =

27. + + = Stacking improves S/N ratio

28. + = Semblance Analysis “Semblance” + X Twtt (s)

29. + = Semblance Analysis + X Twtt (s) V3V3 V1V1 V2V2 V Peak energy