1. Department of Earth and Space Sciences, University of Washington, Box 351310, Seattle, WA 98195, USA.
2. Geology, Minerals, Energy, and Geophysics Science Center, U.S. Geological Survey, 350 N. Akron Road, Moffett Field, CA 9403, USA.
3. Department of Geology, Portland State University, 1721 SW Broadway, Portland, OR 97201, USA.
4. Earthquake Science Center, U.S. Geological Survey, P.O. Box 158, Moffett Field, CA 94035, USA.
5. Department of Applied Mathematics, University of Washington, Box 353925, Seattle, WA 98195, USA.
6. Department of Earth Sciences, University of Oregon, Eugene, OR 97403-1272, USA.
7. Department of Civil and Environmental Engineering, University of Washington, Box 352700, Seattle, WA 98195, USA.