That was a very good show. I saw the post here just 10 minutes before it started. What luck!!

"Seems to me, some trenching work, or something, is in order to determine the risk.. but of course, that doesn't really tell you when the next one might happen..."

The problem with a fault like the Puente Hills is that it is a blind thrust. It never reaches the surface, so there is nothing to trench. The best that can be done (AFAIK) is a detailed seismic sounding with explosive charges, which, IIRC is how the fault was discovered in the first place.

BTW, those animations are available online at the Terrashake home page, where I picked them up months ago already. WARNING, large files.

http://visservices.sdsc.edu/projects/scec/terashake/

Brian