Currently, there is a significant campaign being undertaken in southern California to increase public awareness
and readiness for the next large earthquake along the San Andreas Fault, culminating in a large-scale
earthquake response exercise. The USGS ShakeOut scenario is a key element to understanding the likely
effects of such an event. A source model for a M7.8 scenario earthquake has been created (Hudnet et al.
2007), and used in conjunction with a velocity model for southern California to generate simulated ground
motions for the event throughout the region (Graves et al. 2008). We were charged by the USGS to provide
one plausible realization of the effects of the scenario event on tall steel moment-frame buildings. We have
used the simulated ground motions with three-dimensional non-linear finite element models of three buildings
(in two orthogonal orientations and two different connection fragility conditions, for a total of twelve
cases) in the 20-story class to simulate structural responses at 784 analysis sites spaced at approximately
4 km throughout the San Fernando Valley, the San Gabriel Valley and the Los Angeles Basin. Based on
the simulation results and available information on the number and distribution of steel buildings, we have
recommended that the ShakeOut drill be planned with a damage scenario comprising of 5% of the estimated
150 steel moment frame structures in the 10-30 story range collapsing (8 collapses), 10% of the structures
red-tagged (16 red-tagged buildings), 15% of the structures with damage serious enough to cause loss of life
(24 buildings with fatalities), and 20% of the structures with visible damage requiring building closure (32
buildings with visible damage and possible injuries). This paper details the analytical study underlying these
recommendations.
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