I spoke with Philip Line of the AF&PA today regarding seismic design with Timber. The current seismic codes originated in California with the help of the Federal Emergency Management Agency (FEMA) and the National Earthquake Hazard Reduction Program (NEHRP). Their main focus was with common types of buildings that experienced problems in earthquakes.

The 1997 UBC has values for Braced Heavy Timber as part of a bearing wall system (R=2.8, Omega=2.2) and as part of a braced frame system (R=5.6, Omega=2.2)

Apparently these or similar values will eventually make it back into ASCE 7 and then the IBC. It may take a couple of code cycles to accomplish it though.

It seems that these numbers are the best bet at this time. In most cases wind will likely govern anyway.