1. Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA
2. Institute for Geophysics, University of Texas at Austin, Austin, Texas 78758, USA
3. Scripps Institution of Oceanography, University of California–San Diego, La Jolla, California 92037, USA
4. Nevada Seismological Laboratory, University of Nevada–Reno, Reno, Nevada 89557, USA
5. Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA
6. Department of Earth Sciences, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada