1. 1Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan, U.S.A.
2. 2Department of Earth, Environmental, and Planetary Science, Rice University, Houston, Texas, U.S.A.
3. 3Department of Geophysics, Stanford University, Stanford, California, U.S.A.
4. 4Spanish Seismic Network, National Geographic Institute (IGN), Madrid, Spain
5. 5Now at, Southern University of Science and Technology, Shenzhen, China
6. 6Colorado School of Mines, Golden, Colorado, U.S.A.
7. 7Department of Geosciences, The Pennsylvania State University, State College, Pennsylvania, U.S.A.
8. 8Department of Geoscience, University of Wisconsin–Madison, Madison, Wisconsin, U.S.A.
9. 9Now at, Los Alamos National Laboratory, Los Alamos, New Mexico, U.S.A.
10. 10NORSAR, Kjeller, Norway
11. 11Department of Earth Science, University of California, Santa Barbara, California, U.S.A.
12. 12Now at, California Technological Institute, Pasadena, California, U.S.A.