1. 1Department of Earth Sciences, ETH Zurich, Zürich, Switzerland
2. 2Research School of Earth Sciences, The Australian National University, Canberra, Australia
3. 3Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, Rhode Island, U.S.A.
4. 4Department of Geoscience, University of Wisconsin-Madison, Madison, Wisconsin, U.S.A.
5. 5Lawrence Livermore National Laboratory, Livermore, California, U.S.A.
6. 6University of Alaska Fairbanks, Fairbanks, Alaska, U.S.A.
7. 7Department of Earth Sciences, University of Cambridge, Cambridge, United Kingdom
8. 8U. S. Geological Survey, Menlo Park, California, U.S.A.
9. 9Department of Applied Mathematics and Statistics and Department of Geophysics, Colorado School of Mines, Golden, Colorado, U.S.A.
10. 10Department of Geosciences and Program in Applied and Computational Mathematics, Princeton University, Princeton, New Jersey, U.S.A.
11. 11Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan, U.S.A.
12. 12Department of Earth and Planetary Science, University of California at Berkeley, Berkeley, California, U.S.A.
13. 13Department of Physics and Department of Earth Sciences, University of Toronto, Toronto, Canada
14. 14Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah, U.S.A.