1. 954 National Center, U.S. Geological Survey, Reston, Virginia 20192, Geophysical Laboratory and Center for High Pressure Research, Carnegie Institution of Washington, 5251 Broad Branch Rd., N.W., Washington, D.C. 20015, 956 National Center, U.S. Geological Survey, Reston, Virginia 20192, and MS/977 U.S. Geological Survey, Menlo Park, California 94025