Collaborative Research: San Andreas Scientific Drilling Project: High Resolution Studies of Fault-Zone Process

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9814605McEvillyThis award is one component of a comprehensive proposal to drill a 4-km deep hole into the San Andreas fault. The drill site is close to the hypocenter of the 1966 M~6 Parkfield earthquake, where the San Andreas fault slips through a combination of small-to-moderate earthquakes and aseismic creep. The project involves about 100 scientists from the U.S. and abroad and would be conducted in collaboration with the U.S. Geological Survey (USGS), the U.S. Department of Energy (DoE) and foreign institutions. This particular project covers half of a two-part cooperative and collaborative pre-drilling fault-zone characterization program at Parkfield. These two integrated pre-drilling projects are critical-path activities to acquire data that will define much of the downhole experimental program. The goals of the project are twofold: to determine the absolute locations of the drilling target earthquakes with sufficient accuracy and precision to assure a successful second stage of drilling, and to define systematics (space-time-magnitude) in microseismicity at small-scale (M0, recurrence times of weeks to months) in the drilling target volume of the fault zone. The proposed collaborative work involves (a) reanalysis of existing seismic data, (b) operation of a 15-station surface "calibration" seismic array, (c) installation of 3 new borehole stations near the drilling site, and (d) collaborative analysis of data from the new efforts. This information will be used to determine the drilling plan and engineering specifications for the hole, and to optimize the experiments to be conducted in the active fault zone.