Preliminary Heat Flow Measurements from Plate Boundary Observatory Boreholes along the San Andreas Fault System
Abstract
Knowledge of the subsurface thermal regime is critical for understanding lithospheric rheology, fault mechanics and geodynamic processes. We report new heat flow values from boreholes drilled during the installation of borehole strain meters as part of the Plate Boundary Observatory (PBO) help constrain the role of temperature in determining the spatial and temporal pattern of deformation within along strike-slip faults in California. The new boreholes sites along this plate boundary system are clustered in the San Francisco Bay Area (n=5), San Juan Batista (n=5), Parkfield (n=7), and Anza (n=5). The boreholes vary in depth from 97 to 245 m. Temperature profiles were measured in each borehole and more than 899 thermal conductivity measurements were determined from drill cuttings and core samples. Heat production measurements are currently in progress. Temperature gradients have been corrected for the perturbing effects of terrain and combined with thermal conductivity to form thermal resistance plots and calculate heat flow. In general these plots indicate constant heat flow in the lower parts of the holes consistent with conductive heat transfer. Overall heat flow values are consistent with elevated heat flow that characterizes much of the California Coast Ranges. This study will help constrain the role of temperature in determining the spatial and temporal pattern of deformation within and along strike-slip faults in California.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.T13C1900M
- Keywords:
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- 8106 TECTONOPHYSICS / Continental margins: transform;
- 8130 TECTONOPHYSICS / Heat generation and transport