Cracking an Open Safe: HAZUS Vulnerability Functions in Terms of Structure-Independent Spectral Acceleration

The HAZUS-MH Technical Manual provides a method and data for calculating earthquake loss to ordinary buildings using in part the capacity spectrum method (CSM) of structural analysis, but it does not provide tabular results relating loss to structure-independent intensity measures such as S(a)(0.3 sec,5%) or S(a)(1.0 sec,5%), and no procedure for doing so is offered. It is a minor challenge to perform HAZUS-MH loss calculations outside of HAZUS-MH, owing to the sometimes iterative nature of CSM. A technique to calculate mean loss (here, casualty rates in ordinary buildings) as a function of site-soil-adjusted S(a)(0.3 sec,5%) and S(a)(1.0 sec,5%) is presented that honors all HAZUS-MH methods and data. The resulting seismic vulnerability functions are available at www.risk-agora.org as a resource for open risk modeling. Such vulnerability functions facilitate loss analyses by de-coupling the calculation of hazard from that of loss given hazard.