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Earth, Planets and Space
Fig. 4 | Earth, Planets and Space

Fig. 4

From: In situ stress magnitude and rock strength in the Nankai accretionary complex: a novel approach using paired constraints from downhole data in two wells

Fig. 4

Best-fit values (taken from the lowest residual of predicted versus observed breakout width) of a S Hmax and b UCS from our analysis as a function of depth. For both a and b, filled black circles indicate values associated with the best fit for the S hmin gradient defined by leak-off tests (green line); error bars show the range associated with S hmin of ±2 MPa from gradient (see text for details). Hydrostatic pore pressure (blue line), overburden stress (black line), and the limit on S Hmax for thrust failure (red line) are shown for reference. c Values of UCS (black-filled circles) determined from our analysis (b) versus P-wave velocity from logging data. Also shown are empirical V p–UCS relations for shale [after Chang et al. (2006) using data from Lal (1991) (1) and Horsrud (2001) (2–5)] (gray lines) and the results of triaxial tests on core samples from the Nankai margin (black open circles) (Olcott and Saffer 2013)

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