| In this work, the role of uncertainty in a probabilistic earthquake loss estimation is studied. In order to quantify the uncertainty associated with earthquake loss estimation (ELE), a sensitivity analysis is completed, assuming alternative estimates for different parameters and models in the ELE process. The parametric and modeling estimates are varied one-by-one and the effects on the calculations of average annual loss (AAL) and worst case loss (WCL) are analyzed. These losses are generated via a loss exceedance probability (EP) curve. This study is unique in that it uses a regional loss estimation model, HAZUS, with pre-processing and post-processing software modules to estimate direct economic losses to homeowners and the insurance industry in the Oakland, California region. A probabilistic seismic hazard analysis (PSHA) is mimicked through the use of the pre-processor (Scenario Builder) and post-processor (EP Maker) in the study. Within this sensitivity analysis, annual recurrence of earthquakes, attenuation models for ground motion, soil mapping schemes, and exposure and vulnerability parameters for residential structures are considered. Additionally, techniques to incorporate expert opinion on the vulnerability of structures, the benefits of structural mitigation, and the costs of mitigation into the probabilistic seismic risk assessment are introduced. Conclusions are three-fold. First, the earthquake loss estimation process is very uncertain, producing estimates of direct economic loss that are most sensitive to the ground motion attenuation in the Oakland, California region. Second, the residential structural mitigation studied, bolting a low-rise wood frame structure to its foundation and bracing its cripple wall, is extremely worthwhile for a homeowner to complete, using a straightforward cost-benefit approach. Finally, the homeowner will have to cover the majority of the loss on an average annual basis under various insurance deductible and limit level schemes. |
