1. Geology Department, San Jose State University, San Jose, CA 95192-0201, USA.
2. U.S. Geological Survey, Earthquake Science Center, Pasadena, CA 91106, USA.
3. Berkeley Geochronology Center, Berkeley, CA 94709, USA.
4. University of California, Berkeley, Berkeley, CA 94720-4767, USA.
5. Western Washington University, Bellingham, WA 98225, USA.
6. U.S. Geological Survey, Earthquake Science Center, Menlo Park, CA 94025, USA.