1. Nevada Seismological Laboratory, University of Nevada, Reno, 1664 North Virginia Street, Reno, Nevada 89503, rhatch@nevada.unr.eduken@unr.edu
2. Department of Earth and Environment, Boston University, 685 Commonwealth Avenue, Boston, Massachusetts 02215, rea@bu.edu
3. Also at Nevada Seismological Laboratory, University of Nevada, Reno, 1664 North Virginia Street, Reno, Nevada 89503.
4. UC Berkeley Seismological Laboratory, University of California, Berkeley, McCone Hall, 215 Haviland Path #4760, Berkeley, California 94720, cruhl@berkeley.edu