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Testing Fundamental Theories of Earthquakes and Faulting: The San Andreas Fault Observatory at Depth

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Date and time Feb 15, 2007
from 04:10 PM to 05:00 PM
Location McLennan Physics (MP) 102
Host Sabine Stanley

Mark Zoback

The SAFOD (San Andreas Fault Observatory at Depth) main borehole has been drilled through multiple active traces of the San Andreas fault zone at a depth of 3.2 km in central California where repeating microearthquakes define the active fault at depth. In this talk I will provide an introduction to the goals of the experiment, the status of drilling, sampling and downhole measurement activities and an overview of the initial scientific results.  Geophysical measurements in the borehole reveal the San Andreas Fault zone to be relatively broad (~250 m) with discrete shear zones where localized deformation is taking place. There are no indications of anomalous pore pressure in the core of the fault zone. Stress and heat flow measurements in the SAFOD main hole and co-located pilot hole indicate that the San Andreas Fault is a weak fault in an otherwise strong crust, confirming three decades of inferences about fault strength from heat flow and stress orientation measurements at shallower depth and greater distance from the fault. Construction of the multi-component SAFOD observatory is now underway. This instrumentation will make it possible to study rupture nucleation, propagation and arrest directly within the fault zone.
Affiliation Stanford University
Contact Name Sabine Stanley
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