1. Seismic interferometry: a comparison of approaches Kees Wapenaar Deyan Draganov Joost van der Neut Jan Thorbecke Delft University of Technology

2. Contents Essentials of seismic interferometry Interferometry with multiple sources Interferometry with multiple receivers Interferometry with multiple scatterers

3. Contents Essentials of seismic interferometry Interferometry with multiple sources Interferometry with multiple receivers Interferometry with multiple scatterers

5. Cross-correlation

6. Cross-correlation result is equal to impulsive reflection response

7. Cross-correlation

8. Simplifying assumptions: Direct arrival at x A correlated with primary at x B Single diffractor Primaries only x A is the specular reflection point

9. Contents Essentials of seismic interferometry Interferometry with multiple sources Interferometry with multiple receivers Interferometry with multiple scatterers

10. Simplifying assumptions: Direct arrival at x A correlated with primary at x B Single diffractor Primaries only x A is the specular reflection point

11. Simplifying assumptions: Direct arrival at x A correlated with primary at x B Single diffractor Primaries only x A is the specular reflection point

12. Cross-correlation

13. Timing error

19. Simplifying assumptions: Direct arrival at x A correlated with primary at x B Single diffractor Primaries only x A is the specular reflection point

20. Simplifying assumptions: Direct arrival at x A correlated with primary at x B Single diffractor Primaries only Responses of many independent sources available

21. Simplifying assumptions: Direct arrival at x A correlated with primary at x B Single diffractor Primaries only Responses of many independent sources available

24. Simplifying assumptions: Direct arrival at x A correlated with primary at x B Single diffractor Primaries only Responses of many independent sources available

26. SEG 2002, Theory of acoustic daylight imaging revisited, p 2269-2272

27. Simplifying assumptions: Direct arrival at x A correlated with primary at x B Single diffractor Primaries only Responses of many independent sources available

28. Assume mutually uncorrelated sources

31. SEG 2002, Theory of acoustic daylight imaging revisited, p 2269-2272

32. 1500 m/s 2000 m/s

35. Conclusions for interferometry with multiple sources Reconstruction of reflection response Arbitrary medium Primaries and multiples Requires many sources that are mutually uncorrelated

36. Contents Essentials of seismic interferometry Interferometry with multiple sources Interferometry with multiple receivers Interferometry with multiple scatterers

37. Cross-correlation

38. Simplifying assumptions: Direct arrival at x A correlated with primary at x B Single diffractor Primaries only x A is the specular reflection point

39. Cross-correlation per receiver, followed by sum over receivers gives However ….. Position of specular reflection point is different for each diffractor, which makes this approach useless

40. 0 t Combine with downward extrapolation and imaging Forward extrapolation of ‘source’ Inverse extrapolation of receiver Cross-correlation

41. 0 t

42. t 0

43. Forward extrapolation of ‘source’ Inverse extrapolation of receiver Cross-correlation Integrate along receivers Repeat for all subsurface points Ghost

44. Schuster, EAGE, 2001 Artman et al., EAGE 2004 Draganov et al., SEG 2004, Wednesday afternoon, Poster presentation Mig P3.4

45. Conclusions for interferometry with multiple receivers No reconstruction of reflection response possible. Instead: imaging of subsurface reflectors Arbitrary medium Primaries only Hence, multiples are imaged as ghosts Requires small number of sources

46. Contents Essentials of seismic interferometry Interferometry with multiple sources Interferometry with multiple receivers Interferometry with multiple scatterers

47. Diffuse wavefield: Weaver and Lobkis, 2001, Phys. Rev. Lett. 87

49. Conclusions for interferometry with multiple scatterers Reconstruction of reflection response (Green’s function) Random medium Primaries and multiples Requires small number of sources

50. Multiple sources Multiple receivers Multiple scatterers Output Reflection response Imaged reflectors Green’s function Medium assumptions none random Multiples (coda) yes no yes Sources many few