1. Department of Geological Sciences, University of Southern California, Los Angeles, CA 90089-0740.
2. U.S. Geological Survey, 525 South Wilson Avenue, Pasadena, CA 91106.
3. Seismological Laboratory, California Institute of Technology, Pasadena, CA 91125.
4. U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025.
5. U.S. Geological Survey, Denver Federal Center, Denver, CO 80225.
6. California Divison of Mines and Geology, 630 Bercut Drive, Sacramento, CA 95814.