[MIS22-P03] Estimation of in-situ stress by a new analysis method of Diametrical Core Deformation Analysis (DCDA)
Keywords:DCDA, core sample, principal stress
The new analysis method is based on an assumption that principal stresses are in horizontal plane and a vertical direction. Then circumstance distribution of core diameter is given by a theoretic equation with SHmax, Shmin and vertical stress (Sv). We can get the optimum SHmax and Shmin values and the azimuth analytically by fitting to the observed core diameter by this equation. In this study, we adopted this new method to three cores from a vertical borehole at depths of ~1540 mbsf in site C0009 drilled during the IODP Expedition 319 and estimated the principal stress magnitudes and orientation. Moreover, we compared this result to other results measured by other methods at same depth.
As a result, azimuth of SHmax was N140°, SHmax and Shmin magnitudes were ~65MPa, 42MPa (average of three cores), respectively. The result of SHmax azimuth was consistent to that from breakout. In particular, the SHmax and Shmin magnitudes estimated by the new method were reasonable, and showed the same stress regime with the others. It suggests the new analysis method may be valid.