Spectra Acceleration : Measures what is experienced by a building during an earthquake, by referencing a particle mass on a mass-less vertical rod having the same natural period of vibration as the building
New York City Government, New York City Natural Hazard Mitigation Plan, Appendix B: Glossary, New York, USA 2009. http://www.nyc.gov/html/oem/downloads/pdf/hazard_m itigation/appendix_b_glossary.pdf, (ND/ Gen - Amer) {894}