Risk Analysis Using Rupture-to-Rafters Simulations: Inferring Probabilities of Scenario Earthquakes from the Uniform California Earthquake Rupture Forecast

Probabilistic seismic hazard analysis [PSHA, e.g., Cornell (1968); Anderson and Trifunac (1978); McGuire (1977); McGuire (1995)], typically used in risk assessment and hazard mitigation, has so far relied on ground motion prediction equations (GMPEs), also called attenuation relations [e.g., the next generation attenuation relations or NGA by Campbell and Bozorgnia (2008); Chiou and Youngs (2008); Boore and Atkinson (2008); Abrahamson and Silva (2008)] to arrive at the expected level of shaking at a site over a time horizon. GMPEs are regression relations on measurements of peak shaking intensities from globally recorded earthquakes. Unfortunately, the sparsity of records from large magnitude earthquakes at short distances or in deep sedimentary basins renders the predictions from these relations highly uncertain. Additionally, GMPEs do not consider source effects such as rupture directivity and slip distribution. The non-unique definition of source-to-site distance, especially for large magnitude earthquakes where the rupture may extend hundreds of kilometers and predominant energy release occurs in large slip asperities whose distance from a site may significantly differ from the shortest distance to the rupture, further adds to uncertainty in predictions. Perhaps most importantly, the variance of the estimates of the nonlinear response of a structure (especially complex structures with multiple dominant modes) from a single ground motion intensity measure using fragility curves is generally quite high. Fragility curves represent the conditional probability of failure of a structure or component given a ground motion intensity measure. They are typically developed through repeated nonlinear time history analysis of the structure (or component) using available earthquake records, scaled to various levels of shaking intensity. Complex structures such as tall buildings are sensitive to the duration, amplitude and frequency characteristics of the California Institute of Technology, USA, email: [email protected] California Institute of Technology, USA, email: [email protected]