1. Professor, Dept. of Geography/Univ. of California-Santa Barbara, Santa Barbara, CA 93106 (corresponding author). E-mail: hugo@geog.ucsb.edu
2. Professor, Dept. of Civil and Environmental Engineering, Univ. of California-Los Angeles, Los Angeles, CA. E-mail: williamy@seas.ucla.edu
3. Researcher, Centro de Geociencias/Universidad Autónoma de Mexico, Querétaro, Mexico. E-mail: maog@servidor.unam.mx