Piero Poli, Massachusetts Institute of Technology, Cambridge, MA, United States, Paul A Johnson, Los Alamos National Laboratory, Earth and Environmental Sciences: Geophysics (EES-17), Los Alamos, NM, United States, Valentin Marguin, ISTerre Institute of Earth Sciences, Saint Martin d'Hères, France and Robert A Guyer, University of Nevada Reno, Physics Department, Reno, NV, United States