Analysis of In-situ Stress in the Cajon Pass Borehole to 3.5 KM Depth and Technical Planning and Cost Estimation for Phase III

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The Cajon Pass scientific drilling project is aimed at resolving a 20 year-old controversy about he level of shear stress required to cause motion on major plate-bounding faults. Phase II drilling activities ended at a depth of 3.5 km at Cajon Pass in the spring of 1988. This award provides for 1) complete analysis and interpretation of the nearly continuous profile of stress orientation and relative magnitude as a function of depth that was obtained in the Cajon Pass borehole, and 2) an attempt to obtain uncontaminated pore fluids from a depth of 3.5 km at the bottom of the existing borehole and compute bulk permeability and pore pressure. Funds are also provided to enable the principal investigator to participate in hydraulic fracturing tests in the deep borehole the Germans are drilling. This will be an important opportunity to document the state of stress at appreciable depths in an intraplate environment and the knowledge and experience gained by the principal investigator will be of direct benefit to the U.S. Continental Scientific Drilling Program.