San Andreas Fault Observatory at Depth
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The San Andreas Fault Observatory at Depth (SAFOD) is one of three components of the Earthscope Project, funded by the National Science Foundation in conjunction with the USGS and NASA. The SAFOD site is located just north of the town of Parkfield, California. The SAFOD main hole was drilled to a depth of ~3.4 km in 2004 and 2005, crossing the San Andreas near a region of the fault where repeating Magnitude 2 earthquakes are generated.
A goal of this project is to install instruments to record data near the source of these earthquakes. In addition to the installation of these instruments, rock and fluid samples were continuously collected during the drilling process, and will also be used to analyze changes in geochemistry and mechanical properties around the fault zone. The project will lead to a better understanding of the processes that control the behavior of the San Andreas fault, and it is hoped that the development of instrumentation and analytic methods will help evaluate the possibility of earthquake prediction.
Drilling will be done in three phases. Drilling was started in the summer of 2004 (Phase 1), when the hole was drilled to a vertical depth 1.5 km (~4,500 ft), and then the trajectory of the hole was angled toward the fault. Drilling was resumed in summer of 2005, at which point the San Andreas was crossed at a depth of around 3 km. Phase 3 will be conducted in 2007, at which point 1 km (~3,000 ft) of core will be collected from active areas of the fault. Following completion of phase 3 instruments will be placed in the hole to monitor the long term behavior of the fault.
