The Salt Lake Tribune published an article recently on some trenching activity by the Utah Geologic Survey and the USGS to better date past movements on this active fault.
From the USGS Newsroom:
USGS scientist Ken Hudnut fills us in on how science created the theoretical magnitude 7.8 earthquake behind the Great Southern California ShakeOut—the largest earthquake preparedness drill in U.S. history, coming Nov. 13—and what such an earthquake would do to downtown Los Angeles.
Seems like they did it right wiith this study. They had multiple teams independenlty come up with the ground shaking model, then had different structural engineers who are experts in seismic design of large buildings review the tall buildings in the L.A. area for the design earthquake. They say that buildings would likely come down in the 7.8 magnitude event. Click through to watch the video interview from the USGS.