1. U.S. Geological Survey, Albuquerque Seismological Laboratory, Albuquerque, New Mexico, U.S.A.
2. Project IDA, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, U.S.A.
3. Incorporated Institutions for Seismology, Washington, District of Columbia, U.S.A.
4. Royal Netherlands Meteorological Institute (KNMI), De Bilt, Netherlands