Hi Don,
This got me thinking about extensional/compressional earthquakes on the San Andreas and to their possible relation to strike-slip earthquakes along the San Andreas. Do you know off hand if the focal mechanism of the 5 something foreshock to the Loma Prieta earthquake near Lexington Resevior was compressional or strike slip?

Also, if the the 1838 SF Pennisula was about a 7 and on the San Andreas; and in only 70 years the same section moved 2-3 meters in the 1906 event.
Maybe the 1838 had a good percentage of compressional/ and or extensional movement. Or maybe the 1838 wasn't on the San Andreas but on a nearby fault and just caused superficial cracking of the San Andreas that was noted in 1838. Or maybe, stress build-up on the fault isn't constant and 2-3 meters of strike slip movement can build up either much quicker or slower then what would be a long term average.
Thanks, Steve S.
p.s- I haven't told much about myself on my few posts. I have had a life long interest in the outdoors including "field trip" geology. Depending on who's asking my current occupations are: home-maker, real-estate investor, and job seeker. I have a BA in Psychology and might return back to a college or university in the near future.