Scenario loss earthquake damageability analysis

The financial vulnerability of properties is often determined for specific, scenario earthquakes. The influence of three separate issues on damage to two portfolios are explored: specification of the earthquake considered; specification of the resulting site ground motions; and characterization of the resulting building damageability. A site in San Francisco is considered for a range of building vulnerabilities from very low to very high. Scenario losses are developed for the maximum credible earthquakes on the San Andreas and Hayward faults. Several different assumptions are used to characterizing these earthquakes, including single magnitude values and logic tree characterizations, and the ground motion at the site, including the average value and a probability distribution. Building damageability estimates are made for each different characterization of the scenario earthquake using median, average and 10% exceedance measures of damageability. The results shown how significant the selection of the particular scenario magnitude, site ground motion characterization, and damageability values are to the final results; high values can be as much as four times the low values, all assuming exactly the same earthquake environment and building damageability. It is recommended that the scenario be defined in terms of a logic tree formulation of possible earthquakes to assure that all possible magnitudes are considered, that a probability distribution be used to characterize the building site's ground motion, and that the damageability estimation procedure fully considers uncertainties in both the site ground motion and building damageability in a consistent statistical manner. Copyright (C) 1999 John Wiley & Sons, Ltd.