New Heat Flow Values Along the San Andreas Fault System

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EAR-00877577Harris, RobertThe investigators at University of Utah will conduct a thermal investigation with the U.S.G.S of the San Francisco Bay Area along the San Andreas, Hayward and Calaveras faults. Thermal measurements will be collected in boreholes currently scheduled for drilling as part of the 'Mini Plate Boundary Observatory' experiment for the emplacement of borehole strainmeters. The field component of the study consists of thermal logging and the collection of drill cuttings and rock samples for the determination of thermal physical rock properties. Thermal physical rock properties will be measured using modern laboratory techniques. These boreholes will be re-logged through time to investigate thermal transients (e.g., fluid flow, ground surface temperature changes, thermal events associated with faulting). The modeling component of this project is aimed at resolving: I ) the nature of heat transfer and variation of heat flow along this complex plate boundary; 2) the thermal conditions at both the lower and upper limits of seismicity; and 3) the thermal influence on deformation transients as determined from geodetic data and viscoelastic models of deformation. The field area is ideal for the proposed work because the San Francisco Bay Area has relatively high heat flow (~85 mW m-2) and high strain rates. These two properties maximize opportunities to investigate relationships between the thermal regime of the crust and aseismic transients.