1. SOEE2102 – Geophysical Field Trip and Tutorials Malham Tarn (North Yorkshire) October 2009 Refraction Analysis Sebastian Rost University of Leeds 2009

2. Traveltime Curves

5. Peaceful Nuclear Explosions

6. Traveltime Curves

15. At critical distance: r = 90   i c = critical angle

16. Courtesy of M. Thorne (Univ. Utah) Seismic Wavefield and Seismic Raypaths

17. Traveltimes Direct wave: (from velocity = distance / time ) x

18. Refracted Wave: Snell’s Law

19. Different ways to express the refracted traveltime curve Intercept time

20. Crossover distance: T direct = T refracted X cross > 2z

21. Intercept Times 11 22  1c

22. General multi-layer formula Layer thickness: z Layer velocity: V

24. Up-Dip Down-Dip Q Q

25. Combining Up-Dip and Down-Dip shoots withand V d and V u are apparent velocities!

26. Field Experiment

28. Shot point geometries 12 element geophone spread Possible shot point locations

29. Off end reverse shot

30. Sat On end Forward

31. Sat On end reverse

35. Traveltime picks (from Claritas)

36. Traveltime Curves