Comparative Assessment of Civil Infrastructure Network Performance under Probabilistic and Scenario Earthquakes

The intensity of the seismic demand in a vulnerability assessment of an engineered system can be described in terms of either its annual probability of being exceeded or a scenario earthquake. A probabilistically stated hazard (e.g., one with a return period of 2,475 years) represents an aggregation of numerous earthquakes and may not represent the spatial distribution of seismic intensity from a severe earthquake over a region correctly, making its application to performance evaluation of a large-scale distributed civil infrastructure system questionable. A scenario earthquake models the spatial intensity correctly, but conveys no quantitative measure of the seismic risk. This paper examines the use of probabilistic seismic hazard analysis and corresponding scenario earthquakes as a basis for vulnerability assessment of a networked system. Following an examination of simple spatially distributed series and parallel system models, a vulnerability assessment of an electrical power network in a region of moderate seismicity in the Central United States offers additional insight into the issue.