1. Department of Earth and Space Sciences, University of Washington, Johnson Hall Rm‐070, Box 351310, 4000 15th Avenue NE, Seattle, Washington 98195‐1310 U.S.A., crowellb@uw.edu
2. Now at Department of Earth Sciences, University of Southern California, Los Angeles, California U.S.A.
3. Instrumental Software Technologies, Inc., 77 Van Dam Street, Suite 9, Saratoga Springs, New York 12866 U.S.A.
4. Centro Sismológico Nacional, Universidad de Chile, Blanco Encalada 2002, Casilla 2777, Santiago, Chile
5. GNSS Research Center, Wuhan University, 129 Luoyu Road, Wuchang District, Wuhan 430079, China