SAFOD is the deep drilling component of EarthScope to address fundamental questions about processes that control faulting and earthquake generation within a major plate-boundary fault. The 3.2 kilometer [2 mile] drillhole through California's famous San Andreas Fault has resulted in the collection of rock samples that are supporting physical and chemical investigations of the active earthquake zone.
San Andreas Fault Borehole
The drill site is ~ 1.8 km SW of the San Andreas fault near Parkfield, CA, near a fault segment that moves through a combination of aseismic creep and repeating microearthquakes and is just north of the rupture zone of the 2004, magnitude 6 Parkfield earthquake, the most recent in a series of events that have ruptured the fault seven times since 1857. The SAFOD borehole extends ~3.2 kilometers vertically and ~1.8 kilometers horizontally to intersect the area of microearthquakes. Sections of coring material have been extracted and the cores are being analyzed by the scientific community. A suite of instruments in the borehole directly measure the physical conditions under which earthquakes occur. The pilot hole is a separate, 2.2-km-deep vertical borehole drilled from the same surface location as SAFOD. For more information visit the ICDP site.
Phase III of SAFOD during the summer of 2007 involved several multilateral holes drilled off of the main hole to obtain continuous core within the San Andreas Fault Zone. A pilot hole, drilled in 2002, is a collaborative effort between the International Continental Drilling Program (ICDP), NSF, and the U.S. Geological Survey.