A Ml 3.5 occurred near San Juan Bautista tonight. The Central San Andreas is
an area where moderate to large quakes are often associated with strong X-class
solar flares. For example, the Loma Prieta (1989) and Morgan Hill earthquakes
(1984) were both within a day of a a great solar flare (X10-20).
More recently, most of the solar flares which were listed in an earlier posting
were followed shortly thereafter by earthquakes along the Central Hayward Fault/
San Andreas system in the M 3.0-4.5 range. Generally, as stated in the original
posting there is a 4-5 day delay between flare and earthquake, so today's event
is a bit early.
Don had also noted unusual creep and magnetic effects in this general region
on 13 August, and was sitting back and waiting. I hope the chair didn't fall out
from under him on this one.
Following are some recent earthquakes in the region as they relate to recent
X-class solar flares:

Year 2000
Flare date/Size Earthquake in Central San Andreas/Hayward fault area
June 6, 2000 X 1.1, X2.3 June 13, 2000 Ml 3.5 37.3N 121.6W San Jose
June 7, 2000 X 1.2
June 18, 2000 X 1.0 June 22, 2000 Ml 3.0.3.1 36.8N 121.3W Tres Pinos, Hollister
July 11, 2000 X 1.0 July 15, 2000 Ml 3.8 37.9N 122.0W Concord
July 12, 2000 X 1.9 July 16, 2000 Ml 3.5 36.8N 121.4W San Juan Bautista
July 14, 2000 X 5.7 July 19, 2000 Ml 3.3 36.5N 121.0W Tres Pinos
Sept 30, 2000 X 1.2 Oct 09, 2000 Ml 3.3 36.7N 121.3W Tres Pinos

Nov 24, 2000 X 2.0, X2.3
Nov 25, 2000 X 1.8
Nov 26, 2000 X 1.9 Dec 01, 2000 Ml 4.3 36.9N 121.6W San Juan Bautista
Mar 2, 2001 X 1.7 none
Apr 2, 2001 X20.0, X1.4, X1.1 Apr 08, 2001 Ml 3.2 36.8N 121.5W San Juan Bautista
Apr 3, 2001 X 1.2 Apr 09, 2001 Ml 3.0 36.7N 121.3W San Juan Bautista
Apr 6, 2001 X 5.6
Apr 10, 2001 X 2.3
Apr 12, 2001 X 2.0 Apr 12, 2001 Ml 3.5 36.9N 121.6W San Juan Bautista
Apr 15, 2001 X14.1
Jun 23, 2001 X 1.2 Jun 24, 2001 Ml 3.1 37.0N 121.1W Los Banos

Of course, other events have occurred in this region which were unrelated to X-class
solar flares. In fact since June 2000 there have been 55 events of Ml>=3 in this
general area - on average about 1 every 8-9 days, so the relation described above
could be an illusion. Nevertheless, we can say that if an X-class flare has occurred
there is a good chance of a Ml>=3 earthquake in the general area of San Juan
Bautista within 5-6 days.