1. Department of Civil Engineering, Universidad de Chile, Blanco Encalada 2002, Santiago, Chile
2. Department of Geology, Universidad de Chile, Plaza Ercilla 803, Santiago, Chile
3. Départament des Géosciences, Ecole Normale Superieure, 24 rue Lhomond, 75005 Paris, France
4. Faculty of Engineering, Universidad de Los Andes, San Carlos de Apoquindo 2200, Santiago, Chile
5. Ph.D. student, Department of Structural Engineering, University of California, San Diego, La Jolla, CA, 92093