1. Los Alamos National Laboratory, Theoretical Division, Los Alamos, New Mexico, USA and Colorado School of Mines, Center for Wave Phenomena, Golden, Colorado, USA. (corresponding author)
2. Los Alamos National Laboratory, Earth and Environmental Sciences Division, Los Alamos, New Mexico, USA.
3. Colorado School of Mines, Center for Wave Phenomena, Golden, Colorado, USA.
4. Lawrence Berkeley National Laboratory, Earth and Environmental Sciences, Berkeley, California, USA.