1. Lamont-Doherty Geological Observatory of Columbia University, Palisades, New York 10964
2. Department of Geology and Geophysics, Massachusetts Institute of Technology, Cambridge 02139
3. Institute of Geophysics, University of Hawaii, Honolulu 96822
4. General Dynamics Corporation, Fort Worth, Texas 76101
5. Department of Geophysics, Stanford University, Stanford, California 94305
6. Bellcomm Corporation, Washington, D.C. 20024