Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5...
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Transcript of Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5...
![Page 1: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/1.jpg)
Expedition 314 SummaryExpedition 314: Sept - Nov, 2007
Logging-While-Drilling dedicated holes at 5 sites
Philippine Sea platemegasplay
top of subducting basement
accretionary prism
forearc basin
![Page 2: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/2.jpg)
Logging While DrillingLogging While Drilling
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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
![Page 4: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/4.jpg)
Site Overview
Philippine Sea platemegasplay
top of subducting basement
accretionary prism
forearc basin
![Page 5: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/5.jpg)
Site C0002: Kumano Forearc Basin and Underlying “inner wedge”
![Page 6: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/6.jpg)
Site C0002 LWD log summary
![Page 7: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/7.jpg)
Checkshot data for C0002
![Page 8: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/8.jpg)
Site Overview
Philippine Sea platemegasplay
top of subducting basement
accretionary prism
forearc basin
![Page 9: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/9.jpg)
Sites C0001 and C0004: Mega-splay thrust sheet
![Page 10: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/10.jpg)
C0001 Log Summary
![Page 11: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/11.jpg)
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 SHmax
SHmax
Shmin
![Page 12: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/12.jpg)
Site C000
1Synoptic view: large horizontal exaggeration
Breakouts well-developed from 60-550 mbsf
Deeper interval has rare breakouts, abundant tensile fractures
![Page 13: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/13.jpg)
Shmax ~ 336˚normal to thrust strike suggests
thrust stress state
… but convergence obliquity must be
taken up elsewhereConvergence at 310˚
- 315˚
SHmax
Shmin
Shmin
SHmax
![Page 14: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/14.jpg)
Site C0003 - stuck and abandoned LWD string
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![Page 16: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/16.jpg)
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Sites C0001 and C0004: Mega-splay thrust sheet
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Site C0004
Thrust fault zone at 250-292 mbsf
Breakouts cross this interval with no significant change in azimuth
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Site C0004
SHmax ~ 320˚
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QuickTime™ and a decompressor
are needed to see this picture.
C0004 main splay fault interval
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Site Overview
Philippine Sea platemegasplay
top of subducting basement
accretionary prism
forearc basin
![Page 22: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/22.jpg)
Site C0006 - toe of wedge
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Site C0006
SHmax ~ 330˚
![Page 24: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/24.jpg)
Site Overview
Philippine Sea platemegasplay
top of subducting basement
accretionary prism
forearc basin
![Page 25: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/25.jpg)
Site C0002: Kumano Forearc Basin and Underlying “inner wedge”
![Page 26: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/26.jpg)
Site C0002
Breakouts are well-developed to 1400 m depth
Mean azimuth = 134°
![Page 27: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/27.jpg)
C0001 C0004 C0006C0002
forearc basin prism toe
![Page 28: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/28.jpg)
These observations are consistent with:
• a compressional and/or transpressional stress state in the outer wedge
SHmax = 1
• an extensional stress state in the Kumano basin AND the underlying inner wedge, at least to 1400 mbsf.
SHmax = 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
![Page 29: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/29.jpg)
Faulting Stress Regimes
Thrust
![Page 30: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/30.jpg)
Stress Regimes from BreakoutsStress 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
extensional compressional +/- strike-slip
![Page 31: Expedition 314 Summary Expedition 314: Sept - Nov, 2007 Logging-While-Drilling dedicated holes at 5 sites Philippine Sea plate megasplay top of subducting.](https://reader034.fdocuments.us/reader034/viewer/2022051821/56649eb65503460f94bc079b/html5/thumbnails/31.jpg)
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?