Hello Don,
I'm back from a SCEC field trip to the San Andreas fault near Wrightwood (and in Wrightwood). More on that later. As for the boreholes...hmmm...I'll do that in an email...

OK, on the field trip Tom Rockwell said that a lady slept through the Izmit earthquake even though it slipped 5 m in her backyard. There was a shelf with delicate objects on it that did not tip over...nor did the delicate objects. Tom thinks that it was areas with discontinuities that produced the strong motion...in certain areas with smooth straight fault the motion was small.

We spent a couple hours yesterday looking at the "damage zone" of the San Andreas where the rock is pulverized...in place...not sheared. This can be taken as evidence for strong ground motion...
Chris