US Geological Survey


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Published in JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 93, NO. B12, PAGES 15,183-15,195, DECEMBER 10, 1988


Hydraulic fracturing stress measurements were made in a 592-m-deep well at Hi Vista, California, 32 km from the San Andreas fault in the western Mojave Desert. The relative magnitudes of the horizontal principal stresses and the calculated overburden stress indicate that the stress regime at this site is transitional between thrust faulting and strike-slip faulting. The azimuths of the induced hydraulic fractureast Hi Vista exhibit considerable scatter, and the indicated direction of them aximum horizontal principal stress ranges from north-northeast to northwest. The measured magnitudes of the horizontal principal stresses and the horizontal deviatoric stress in this well are less than or equal to those measured in a nearby well of comparable depth 4 km from the San Andreas fault. This result contrasts with the increase in these stress components with distance from the San Andreas fault that was observed in a shallower borehole profile in the same area. Marked fluctuations in both stress magnitudes and orientations with depth in the Hi Vista well, however, may result from a localized perturbation to the regional stress regime. No correlation was found to exist in this well between stress magnitudes and either P wave velocities or natural fracture densities, although the low stresses measured at a depth of about 540 m may reflect proximity to an intensely fractured and permeable zone at the bottom of the well.