1. Department of Structural and Geotechnical Engineering, Faculty of Architecture “L. Quaroni,” University of Rome “La Sapienza,” Via Gramsci, 53, 00197 Roma, Italy
2. Department of Civil Protection, National Seismic Survey Office. Via Vitorchiano 2, 00189 Roma, Italy
3. AIR Worldwide Co., 388 Market Street, Suite 610, San Francisco, CA 94111