1. Branch of Earthquake Geology and Geophysic, U.S. Geological Survey, MS/ 977, 345 Middlefield Road, Menlo Park, California 94025
2. Department of Physics, Lafayette College, Easton, Pennsylvania 18042
3. University of California Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550
4. 955 National Center, U.S. Geological Survey, MS/ 955, Reston, Virginia 20192