1. Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting basement accretionary prism forearc basin

2. Logging While Drilling

3. Bulk density/Porosity/Caliper Vp by check shot Data transfer/annular P Sonic velocity Resistivity image LWD (Logging-While-Drilling) Drill bit 1-2 rot/sec

4. Site Overview Philippine Sea plate megasplay top of subducting basement accretionary prism forearc basin

5. Site C0002: Kumano Forearc Basin and Underlying “inner wedge”

6. Site C0002 LWD log summary

7. Checkshot data for C0002

8. Site Overview Philippine Sea plate megasplay top of subducting basement accretionary prism forearc basin

9. Sites C0001 and C0004: Mega-splay thrust sheet

10. C0001 Log Summary

11. Borehole Breakouts: Indicators of Principal Stress Orientations LWD Resistivity Image log Walls of the borehole fracture or “break out” perpendicular to the direction of horizontal maximum compressional stress S Hmax S Hmax S hmin

12. Site C0001 Synoptic view: large horizontal exaggeration Breakouts well- developed from 60-550 mbsf Deeper interval has rare breakouts, abundant tensile fractures

13. Shmax ~ 336˚ normal to thrust strike suggests thrust stress state … but convergence obliquity must be taken up elsewhere Convergence at 310˚ - 315˚ SHmax Shmin SHmax

14. Site C0003 - stuck and abandoned LWD string

17. Sites C0001 and C0004: Mega-splay thrust sheet

18. Site C0004 Thrust fault zone at 250-292 mbsf Breakouts cross this interval with no significant change in azimuth

19. Site C0004 S Hmax ~ 320˚

20. C0004 main splay fault interval

21. Site Overview Philippine Sea plate megasplay top of subducting basement accretionary prism forearc basin

22. Site C0006 - toe of wedge

23. Site C0006 S Hmax ~ 330˚

24. Site Overview Philippine Sea plate megasplay top of subducting basement accretionary prism forearc basin

25. Site C0002: Kumano Forearc Basin and Underlying “inner wedge”

26. Site C0002 Breakouts are well- developed to 1400 m depth Mean azimuth = 134°

27. C0001C0004 C0006 C0002 forearc basinprism toe

28. These observations are consistent with: a compressional and/or transpressional stress state in the outer wedge S Hmax =  1 an extensional stress state in the Kumano basin AND the underlying inner wedge, at least to 1400 mbsf. S Hmax =  2 This does not require a rotation of principal stress axes, only a change in their relative magnitude. Upper 950 m:forearc basin Lower 450 m: prism

29. Faulting Stress Regimes Thrust

30. Stress Regimes from Breakouts Horizontal principal stress axis change is sharp, lies between Sites C0001 and C0002 Consistent with change in relative magnitude of principal stresses extensionalcompressional +/- strike-slip

31. Future Work 1.Constrain stress magnitudes through strength testing of core samples 2.Drill deeper at C0002 (forearc basin site) Will stress axes flip/rotate with depth?