Approximate P-Wave Speed map in the earthquake active region near Parkfield, CA.

Geophysical Fault Identification

SAFOD
Rensselaer IPRPI researchers are participating in a major national cooperative effort, the San Andreas Fault Observatory at Depth (SAFOD) project.

SAFOD will place instrumentation inside the fault with the goal of understanding future earthquakes; more specifically to better understand the processes that produce earthquakes and related geological phenomena.

The project calls for a 4 km hole to be drilled, beginning in summer 2004, through the fault zone near the hypocenter of the 1966 Parkfield, California earthquake. The drill hole is expected to be completed in summer 2006.

Drilling, sampling, and taking downhole measurements within the San Andreas Fault zone are expected to advance scientific knowledge of earthquakes by providing direct observations of a major active fault zone.

Advances in Techniques
Recent advances in recording techniques have enabled scientists to undertake a large scale data collection effort that will include seismic data from many locally recorded microearthquakes.

Along with a prototype data set from the Parkfield project, these data sets will enable the application of new techniques in inverse theory, such as:

• microlocal and time-reversal techniques
• large-scale processing techniques
• imaging algorithms

These methods have shown remarkable success when applied to other environments such as active source seismology where the objective is locating oil fields and seabottom location in ocean acoustics, where the objective is locating oil fields.

SAFOD and IPRPI
Rensselaer IPRPI scientists are participating in an initial step of the project by working to recover an image of the San Andreas Fault in the vicinity of the SAFOD drill site.

Their results will guide SAFOD drillers during their process; researchers also will use the SAFOD data obtained in the vicinity of the drill site to enhance images of the fault region.

Led by Dr. Steven Roecker, Rensselaer professor of geosciences, the IPRPI project includes geoscientists, applied mathematicians, and computer scientists.

The Rensselaer researchers will begin with a relatively high-quality background image provided by tomographic analysis of compressional and shear wave arrival times recorded by the dense deployment of Parkfield Area Seismic Observatory (PASO) recording stations in the neighborhood of the San Andreas Fault.

Major objectives of the project involve generating a solution to the linear elastic equation system and best using this numerical solution for fault identification.

An additional challenge will be to quantify the effects of the imperfect prior information on the image.

At the same time, new tools for accurate earthquake location and subsurface imaging will be created.

Funding
A National Science Foundation (NSF) Collaborations in Mathematical Geosciences award supports the current project by funding undergraduate and graduate students, postdoctoral researchers, as well as contributing faculty.

Research Team Members:
Rensselaer Faculty
Steven Roecker
Margaret Cheney
Joyce Mclaughlin (consultant)

Postdoctoral Fellow
Dan Renzi

Graduate Student
Yi Fang
Polina Jeglova

Undergraduates
Jen Flakker,
Jackie Krajewski
Ashley Shaler

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Inverse Problems Center at Rensselaer
Rensselaer Polytechnic Institute, 110 8th St., Troy, NY 12180-3590.
(518) 276-2145• E-mail: mclauj3@rpi.edu