1. Alejandro Veen is Research Staff Member, IBM T. J. Watson Research Center, Yorktown Heights, NY 10598 . Frederic P. Schoenberg is Professor, Department of Statistics, University of California, Los Angeles, CA 90095-1554 . This material is based on work supported by the National Science Foundation under grant 0306526. We thank Yan Kagan, Yingnian Wu, Ilya Zaliapin, and anonymous referees for helpful comments, and the Southern California Earthquake Center for its generosity in sharing its data. All...