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San Andreas Fault Zone Observatory at Depth



SAFODThe San Andreas Fault Observatory at Depth (SAFOD) is a component of EarthScope. EarthScope will investigate the structure and evolution of the North American continent and the physical processes controlling earthquakes and volcanic eruptions. EarthScope is funded by the National Science Foundation and conducted in partnership with the US Geological Survey.

SAFOD is motivated by the need to answer fundamental questions about the physical and chemical processes controlling faulting and earthquake generation within a major plate-bounding fault. SAFOD will drill and instrument an inclined borehole across the San Andreas Fault Zone to a depth of 3.2 km, targeting a repeating microearthquake source. The drill site is located west of the vertical San Andreas Fault on a segment of the fault that moves through a combination of aseismic creep and repeating microearthquakes (Figure). It lies at the extreme northern end of the rupture zone of the 1966, Magnitude 6 Parkfield earthquake, the most recent in a series of events that have ruptured the fault five times since 1857. The Parkfield region is the most comprehensively instrumented section of a fault anywhere in the world, and has been the focus of intensive study for the past two decades.

(Figure ©:USGS)




North America, U.S.A., United States of America, California, San Andreas Fault Zone, near by Parkfield



35° 58' 26.5'' N, 120° 33' 8.73'' W (Please scroll down to end of page for more information.)


Project Start and End
  • Pilot Hole
    • Begin of drilling June 6, 2002
    • End of drilling July 24, 2002
  • Main Hole, Phase I
    • Begin of drilling June 11, 2004
    • End of drilling October 6, 2004
  • Main Hole, Phase II
    • Begin of drilling June 8, 2005
    • End of drilling August 28, 2005
  • Main Hole, Phase III
    • Begin of drilling June 14, 2007
    • End of drilling September 15, 2007


Programs and Funding


Principal Investigators
  • Mark D. Zoback, Stanford University, School of Earth Sciences, Department of Geophysics
  • Stephen Hoyt Hickman, U.S. Geological Survey at Menlo Park, Earthquake Hazards Program, Northern California
  • William L. Ellsworth, U.S. Geological Survey at Menlo Park, Earthquake Hazards Program, Northern California


Partners and Contractors



Active Faulting, California, Directional Drilling, Downhole Monitoring, Earthquakes, ICDP-2004/04, Parkfield, SAFOD, San Andreas Fault, U.S.A.


Current State





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