1. Department of Civil and Environmental Engineering; Massachusetts Institute of Technology; Cambridge Massachusetts USA
2. Department of Earth, Atmospheric and Planetary Sciences; Massachusetts Institute of Technology; Cambridge Massachusetts USA
3. Now at Department of Chemical Engineering and Materials Science; University of Southern California; Los Angeles California USA
4. Department of Earth and Planetary Sciences; Harvard University; Cambridge Massachusetts USA
5. Institute of Geophysics and Planetary Physics; University of California, San Diego; La Jolla California USA
6. Now at Earth Sciences Division; National Science Foundation; Washington District of Columbia USA
7. Department of Earth Sciences; University of California; Riverside California USA
8. Jackson School of Geosciences; University of Texas at Austin; Austin Texas USA