Thanks Michael! Very interesting! I've included a link to an article in the San Jose Mercury News with some additional info. I'm guessing that the reference in your post to a 2003 M6.5 is the San Simeon earthquake - which, of course, occurred quite some distance from the SAF. At least I can't recollect another quake in 2003 on the SAF. The 2004 quake is apparently Parkfield.

Most of you know that Parkfield earthquakes immediately preceded the 1857 quake referred to, and is near the northern terminus of the rupture (?)- a 225 mile long surface rupture, and also, according to many, near the actual epicenter of the 1857 quakes. Please correct me if I have any of that wrong.

Also - just a little odd that your article states that "Nadeau first discovered tremors . . . in 2005". The article itself seems to strongly suggest that they were being recorded since before 2003 ("Scientists noticed the frequency of the tremors doubled after the 2003 quake . . . ").

Susan Hough monitors and occasionally posts to the sci.geo.earthquakes newsgroup. She is with Pasadena USGS and many readers here know her as the expert the media usually go to after significant SoCal quakes. She might be prompted to expound a little on the newsgroup. Anyway - thanks for the heads-up, Michael.

• San Jose Mercury News