1. Lamont-Doherty Geological Observatory, Columbia University, Palisades, New York 10964
2. Department of Earth and Planetary Sciences, Massachusetts Institute of Technology, Cambridge 02139
3. Hawaii Institute of Geophysics, University of Hawaii, Honolului 96822
4. Lamont-Doherty Geological Observatory
5. Fort Worth Division of General Dynamics, Fort Worth, Texas 76101
6. Department of Earth and Planetary Sciences, Massachusetts Institute of Technology
7. Hawaii Institute of Geophysics