Although smaller earthquakes are far more numerous, large earthquakes (M > 7.5) account for most of the slip in plate tectonics. That is, the number of earthquakes generally decreases by a factor of ten for each unit increase in magnitude, but the energy of an individual earthquake increases by a factor of 32. If we assume that M 8.0 is the largest earthquake magnitude that an earthquake can have in California, then there is three times as much radiated energy in the M 7 to 8 earthquakes as there is in all other earthquakes smaller than M 7. Therefore, we see that although large earthquakes are infrequent, they are the major actors in plate tectonics; in this sense, large earthquakes are inevitable. What will happen when one of these large magnitude earthquakes hits one of our cities? Recent engineering studies have concluded that since many structures weathered the onslaught of the 1994 M 6.7 Northridge earthquake and the 1995 M 6.9 Kobe earthquake, that our building standards are adequate to handle the coming earthquakes. However, can we expect to survive a M 7.9 earthquake with 32 times as much energy? There seems to be an inconsistency between earth scientists and earthquake engineers about the significance of large magnitude earthquakes. Much of our work is aimed at a more complete understanding of the nature of ground shaking close to large earthquakes. That is, ground motions from large earthquakes are simulated by propagating waves through 3-dimensional earth structure models. The models produce realistic estimates of the large displacements (several meters in several seconds) that occur in great earthquakes. While accelerations that are associated with these large displacements may not be large enough to cause failure of strong, shear-wall structures, they may cause severe deformations in flexible buildings that rely heavily on ductility for their performance in large earthquakes. This work is closely coordinated with Prof. John F. Hall. We (Jing Yang) are investigating the potential performance of steel moment-resisting-frame buildings in large subduction zone earthquakes. We have simulated the deformations and damage that would have occurred to such buildings in the M 8.3 Tokachi-Oki earthquake (2003). Although there we no such buildings present on the island of Hokkaido during this earthquake, there were 275 strong motion records which we are using as the basis of our study. In addition, we are using this data as the basis of an empirical Green's function study of the potential effects of a giant (M>9) subduction earthquake on high-rise buildings in the cities of Seattle, Portland, and Vanvouver. We (Anna Olsen) are also studying the performance of steel moment-resisting-frame buildings and base-isolated buildings in simulations of large crustal earthquakes in California. These include simulations of the 1906 San Francisco earthquake (collaboration with Brad Aagaard) and simulations of several plausible earthquakes in the Los Angeles Basin.