1. Department of Physics; University of Colorado; Boulder; Colorado; 80309; USA
2. School of Earth and Space Exploration; Arizona State University; Tempe; Arizona; 85287; USA
3. Computational Infrastructure for Geodynamics; California Institute of Technology; Pasadena; California; 91125; USA
4. School of Mathematical Sciences; Monash University; Clayton; Victoria 3800; Australia
5. Seismological Laboratory; California Institute of Technology; Pasadena; California; 91125; USA