The central scientific objective of SAFOD is to study the physical and chemical processes that control deformation and earthquake generation within an active plate-bounding fault zone. Hence, the principal reasons for drilling into the San Andreas Fault have been to conduct extensive investigations in situ and on exhumed materials that are representative of the fault at the pressures, temperatures, and conditions at which earthquakes nucleate. In particular, through an integrated program of downhole sampling, measurements, and long-term monitoring, SAFOD was designed to (1) measure stress, permeability, and pore pressure conditions in situ, (2) deter- mine frictional behavior, physical properties, and chemical processes controlling faulting through laboratory analyses of fault rocks and fluids, (3) characterize the three-dimensional volume of crust containing the fault, (4) directly monitor strain, pore pressure, and near-field seismic radiation during the cycle of repeating microearthquakes, and (5) observe earthquake nucleation and rupture processes in the near field.
Requests for core samples from the “10,480” fault zone. Investigators from around the world can view the core and select samples using a tool developed by EarthScope. Because each sample is unique (a) Simplified geologic cross section along the trajectory of the SAFOD borehole as constrained by surface mapping (courtesy M.Thayer and r.Arrowsmith) and subsurface information.(b)view of the plane of the San Andreas Fault at ~2.7-km depth looking to the northeast. The red, blue, and green circles represent seismogenic patches that produce regularly repeating target microearthquakes. (c) Cross-sectional view of the target earthquakes looking to the northwest, including the trajectory of the SAFOD borehole.