The Varian A-1 well, drilled to approximately 1.5 km depth a few kilometers northwest of Parkfield, California, presents an opportunity for analysis of seismic signals close to the San Andreas fault zone at a location where a large earthquake is predicted. The U.S. Geological Survey has committed funds to open the well so that a seismometer array can be installed for seismic vertical profiling. This project will result in the design, fabrication, purchase, and assembly of a seismic sensor system to be installed in the Varian A-1 well. In addition to its location close to the nucleation zone of major earthquakes, the deep well is an excellent observatory site for sensitive measurements because it is not subject to surface and near-surface seismic noises. This project will contribute to a better understanding of earthquake-generating mechanisms and to improved earthquake prediction capabilities.