San Andreas fault zone drilling project: scientific objectives and technological challenges

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We are leading a new international initiative to conduct scientific drilling within the San Andreas fault zone at depths of up to 10 km. This project is motivated by the need to understand the physical and chemical processes operating within the fault zone and to answer fundamental questions about earthquake generation along major plate-boundary faults. Through an integrated program of coring, fluid sampling, in-situ and laboratory experimentation and long-term monitoring, we hope to provide fundamental constraints on the structure, composition, mechanical behavior and physical state of the San Andreas fault system at depths comparable to the nucleation zones of great earthquakes. The drilling, sampling and observational requirements needed to ensure the success of this project are stringent. These include: 1) drilling stable vertical holes to depths of about 9 km in fractured rock at temperatures of up to 300??C; 2) continuous coring of inclined holes branched off these vertical boreholes to intersect the fault at depths of 3, 6 and 9 km; 3) conducting sophisticated borehole geophysical measurements and fluid/rock sampling at high temperatures and pressures; and 4) instrumenting some or all of these inclined core holes for continuous monitoring of seismicity and a broad range of physical and chemical properties over periods of up to several decades. For all of these tasks, because of the overpressured clay-rich formations anticipated within the fault zone at depth, we expect to encounter difficult drilling, coring and hole-completion conditions in the regions of greatest scientific interest.

Additional publication details

Publication type:
Conference Paper
Publication Subtype:
Conference Paper
San Andreas fault zone drilling project: scientific objectives and technological challenges
Year Published:
Publ by ASME
Publisher location:
New York, NY, United States
Larger Work Title:
American Society of Mechanical Engineers, Petroleum Division (Publication) PD
First page:
Last page:
Conference Title:
Proceedings of the Energy-Sources Technology Conference
Conference Location:
New Orleans, LA, USA
Conference Date:
23 January 1994 through 26 January 1994