1. U.S. Geological Survey, Albuquerque Seismological Laboratory, Kirtland AFB, New Mexico, U.S.A.
2. U.S. Geological Survey, National Earthquake Information Center, Golden, Colorado, U.S.A.
3. Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, U.S.A.
4. Incorporated Research Institutions for Seismology, Washington, D.C., U.S.A.