1. Scripps Institution of Oceanography, University of California, San Diego (UCSD), La Jolla, California 92071 U.S.A., dkilb@ucsd.edu
2. Santana High School, 9915 Magnolia Avenue, Santee, California 92071 U.S.A.
3. University of Utah Seismograph Stations, University of Utah, Salt Lake City, Utah 84112‐0102 U.S.A.
4. U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025‐3591 U.S.A.