1. Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography; University of California; San Diego - 0225, La Jolla California 92093-0225 USA
2. Ecole Normale Superieure de Lyon; 46 Allee d'Italie, 69364 Lyon, cedex 7 France
3. Seismological Laboratory; California Institute of Technology, MC 252-21; Pasadena California 91125 USA
4. Department of Geological Sciences, Snee Hall; Cornell University; Ithaca New York 14853 USA
5. Department of Geology; University of Maryland; College Park Maryland 20742 USA
6. Division of Chemical Sciences, Geosciences, and Biosciences, SC-14, Office of Basic Energy Sciences; U.S. Department of Energy; 19901 Germantown Road, Germantown Maryland 20874-1290 USA
7. National High Magnetic Field Laboratory and Department of Geological Sciences; Florida State University; 1800 East Paul Dirac Drive, Tallahassee Florida 32306-4005 USA