Hydraulic fracturing in situ stress measurements to 2.1 km depth at Cajon Pass, California

Stress measurements to 2.1 km reveal stress changes with depth that cannot be explained by an elastic response to uniform crustal strain. The data at about 1 km depth suggest that the stress is limited by the frictional strength of rock and is perturbed at greater depths by faults which intersect the borehole. The stress data indicate that there is little or no right-lateral shear stress acting on planes parallel to the San Andreas fault.