1. Shear alignment of olivine crystals
Anisotropy
Shear alignment of olivine crystals

2. Shear wave splitting a c

3. Olivine Anisotropy: Basic (A-type)
[1 0 0] (a-axis) parallel to flow direction
(0 1 0) plane parallel to flow plane
Horizontal flow Vsh > Vsv
Vertical flow Vsh < Vsv
Polarization of faster shear wave parallel to flow direction

4. Olivine (a-axis projection)
[0 1 0]
[0 0 1]

5. Olivine (b-axis projection)
[0 0 1]
[1 0 0]

6. Olivine (c-axis projection)
[0 1 0]
A-type: [1 0 0] on (0 1 0)
[1 0 0]
Vertical Shear

7. Olivine (c-axis projection) [1 0 0] on (0 1 0)
Horizontal Shear
[0 1 0]
VSH > VSV
A-type

8. A-type [1 0 0] on (0 1 0)

9. Olivine anisotropy Vp a c b

10. Olivine anisotropy Vs a c b

11. Olivine anisotropy Vs (a-vibration direction is fast)

12. Olivine anisotropy (Karato et al, 2008)
A-type [1 0 0] on (0 1 0)
B-type [0 0 1] on (0 1 0)
C-type [0 0 1] on (1 0 0)
D-type [1 0 0] on {0 k l}
E-type [1 0 0] on (0 0 1)

13. Olivine (c-axis projection)
[0 1 0]
A-type: [1 0 0] on (0 1 0)
[1 0 0]
Vertical Shear

14. A-type [1 0 0] on (0 1 0)

15. Olivine (a-axis projection) (B-type)
[0 1 0]
[0 0 1]
[0 0 1] on (0 1 0)

16. B-type [0 0 1] on (0 1 0)

17. Olivine (b-axis projection) (C-type)
[1 0 0]
[0 0 1]

18. C-type [0 0 1] on (1 0 0)

19. Olivine (a-axis projection) (D-type)
[0 1 0]
[0 0 1]
[1 0 0] on (0 k l): Translation is normal to projection plane

20. D-type [1 0 0] on (0 k l)

21. Olivine (b-axis projection) (E-type)
[0 0 1]
[1 0 0]

22. E-type [1 0 0] on (0 0 1)

23. Olivine anisotropy
Olivine anisotropy

24. Olivine (a-axis projection)
[0 1 0]
[0 0 1]

25. Olivine anisotropy
Olivine anisotropy

26. Olivine anisotropy
Karato group experiments done only up to 2000 H per 106 Si.
Lower asthenosphere conditions allow up to 140,000 H per 106 Si in forsterite.
Explains why Karato sees B- and C-type textures at hydrous conditions.
More data at very hydrous conditions would help.

27. Olivine anisotropy
Expect B-type to predominate if H2O content > 1000 ppm at depth > 200km.
50,000
100,000

28. Olivine anisotropy
Crystal structure of hydrous forsterite shows vacancies concentrated at M1 with proton on O1-O2 edge.
M1 octahedra form chains parallel to c.
Very hydrous conditions in lower asthenosphere might favor deformations that have offsets along c (B-type and C-type).

29. Olivine (a-axis projection) (B-type)
[0 1 0]
[0 0 1]

30. B-type [0 0 1] on (0 1 0)

31. Olivine anisotropy A-type [1 0 0] on (0 1 0) B-type [0 0 1] on (0 1 0)
C-type [0 0 1] on (1 0 0)
D-type [1 0 0] on {0 k l}
E-type [1 0 0] on (0 0 1)
A, D, and E types align a-axis with shear
B, and C-types align c-axis with shear

32. Olivine textures

33. Shear wave splitting a c