PROJECT SUMMARY
This is a proposal to conduct a 4.0-km-deep scientific drilling project into the San Andreas fault zone at Parkfield, California. The scientific rationale for fault zone drilling is to provide direct observational data on the composition, physical state and mechanical behavior of a major active fault zone at depth. Such data will test and constrain a diverse (and continually expanding) spectrum of hypotheses pertaining to faulting and earthquake generation. Moreover, a drill hole within a section of the San Andreas fault that is both creeping and producing numerous microearthquakes will permit direct, continuous monitoring of an active plate boundary fault at depth. The data we propose to collect is essential to better understand the physical and chemical processes controlling the mechanics of faulting and will contribute appreciably to earthquake hazards reduction.
The fundamental scientific issue addressed in this proposal, obtaining an improved understanding of the physical and chemical processes responsible for earthquakes along major fault zones, is clearly of global scientific interest. Throughout the planning process leading to the development of this proposal we have invited participation by scientists from around the world. As a result, the workshops and meetings we have held for this project have involved about 350 scientists and engineers from about a dozen countries.
This proposal follows a previous proposal submitted to the NSF Continental Dynamics (CD) Program in June, 1996 (hereafter referred to as Z&H'96) which laid out the scientific rationale for fault zone drilling and a specific proposal to drill and core to a total depth of 2.5 km in the Parkfield area. In the present proposal we present a revised drilling and coring plan that involves penetrating the fault to a total depth of 4.0 km, thereby addressing one of the principal recommendations of the CD panel to conduct all of the key experiments at depths closer to that of the on-going seismicity. In response to our previous proposal, the CD panel also recommended that we assemble a team of scientists, whose proposals would be evaluated concurrently with this one, to conduct allied investigations critical to the scientific success of this project. Accordingly, in this proposal we provide summary work plans and budgets from over seventy principal investigators proposing:
At the present time, this science team includes 33 principal investigators from 19 U.S. universities, about 15 scientists from the U.S. Geological Survey, several scientists from Lawrence Berkeley and Lawrence Livermore National Laboratories of the U.S. Department of Energy and scientists from 12 institutions in 4 foreign countries. If the proposed project becomes a reality, these numbers are expected to increase.
Although this project is intended as a comprehensive and complete investigation that stands on its own scientific merits, it may also be the first step toward conducting a much more ambitious program of deep (~10 km) drilling and surface-based geological and geophysical site investigations along the San Andreas fault system (see Hickman et al., 1994). By sampling the San Andreas fault zone and making direct measurements of fault zone properties to 4.0 km at Parkfield we will be studying an active plate-boundary fault at a depth where aseismic creep and small earthquakes occur and where a number of the scientific questions associated with deeper fault zone drilling can begin to be addressed. Also, the technological challenges associated with drilling, coring, downhole measurements and borehole instrumentation that may eventually have to be faced in drilling to 10 km can first be addressed at moderate depth and temperature in the Parkfield hole.