1. Department of Geosciences, Princeton University , Princeton, NJ 08544 , USA
2. Independent author
3. Institute of Geology and Geophysics, Chinese Academy of Sciences , Beijing 10029 , China
4. Departments of Applied Mathematics & Statistics and Geophysics, Colorado School of Mines , Golden, CO 80401 , USA
5. Program in Applied and Computational Mathematics, Princeton University , Princeton, NJ 08544 , USA
6. Livermore Computing, Lawrence Livermore National Laboratory , Livermore, CA 94550 , USA
7. Scientific Data Group, Oak Ridge National Laboratory , Oak Ridge, TN 37830 , USA