Proc. IODP, 308, Data report: stress orientations from borehole breakouts, IODP Expedition 308, Ursa area, Mississippi Fan, Gulf of Mexico

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Chapter contents Abstract Introduction Description of breakouts Orientation of breakouts Implications Acknowledgments References Figures F1. Bathymetry, Ursa region. F2. Resistivity images. F3. Breakout orientations, Site U1322. F4. Breakout orientations, Site U1324. PDF file			Previous \| Next doi:10.2204/iodp.proc.308.212.2009 Implications Because the LWD resistivity imaging tool is located ~3 m above the bit and the borehole is drilled at 20–30 m/h, the breakouts must form a few minutes after drilling in order to be imaged. Thus, the breakouts represent a rapid, typically brittle failure mode and measure current in situ stress. Widespread gravitational failure in the Ursa region drilled by IODP (Sawyer et al., 2007) indicates that the maximum principal stress is vertical, which is typical of passive continental margins. Thus, S_Hmax and S_Hmin at Sites U1322 and U1324 are the intermediate and minimum principal stresses, respectively. The approximately north–south S_Hmax at Sites U1322 and U1324 is subparallel to the overall southward-dipping regional slope of the Gulf of Mexico. At Site U1322, S_Hmin is perpendicular to en echelon extensional fractures along the margin of a nearby submarine landslide. Top of page \| Previous \| Next

Implications