ichael,

This was not an insignificant earthquake for that area of Southern
California. The last event in the region 34-35N 118-119W which was
larger occurred as an aftershock to the Northridge earthquake on
27 April 1997, more than 4 years ago. The last earthquake of similar
size in this area occurred on Jan 14, 2001 (Ml 4.2).
I might add that this is near the boundary of the Santa Clarita
prediction Don had made in late August. In that forecast, he had
noted:

"The magnitude is 2.5Md to 3.7Md. However in the event of a geomagnetic storm
on or about 08/29/2001, or a hurricane on the east coast the magnitude could
be greater. As to how much greater is the tricky part. I would say that at
the max it shouldn't be over a 5.7Md. More likely around 4.7Md."

The suggestion was that a large earthquake in the area would be
dependent on solar/geomagnetic effects. The Space Environment Center (SEC)
observed a M9.5 (nearly an X-class) flare this afternoon. This flare
was the largest since an X5.3 on August 25, 2001 and the largest since
Don posted this prediction. The parameters of today's flare from SEC are:

Flare # BEGIN MAX END CLASS
2160 + 2040 2045 2048 M9.5

See:
http://sec.noaa.gov/ftpdir/indices/events/20010909events.txt
and
http://sec.noaa.gov/today.html

Recall that a Ml 2.9 did occur in Don's predicted area in the
time frame of his prediction. There has been a series of smaller
earthquakes in the area since then, however, so this appears
to be a continuation of that series.

You might also recall that the area West of Los Angeles was specifically
noted in the far-field forecast from the Pacific-Antarctic Rise of 2 September
as a region where far-field triggering was to be expected. That forecast had
stated:

" Local areas in the U.S. which may experience a regionally
significant or moderate quake or increased activity:
(Expected maximum magnitudes increase by 0.5 units)

Southern California 115-119.5W 32-35N
A section between 34-36N from Virginia, New Madrid, Arizona,
Southern California"

and

" In the United States seismic events in Southern California
ond off the coast of Northern California in the Mendocino area
often follow earthquake in this area of the Pacific."

and

"Areas where the wave-front is parallel to the local
faulting have experienced large events following earthquakes
in this region of the Pacific-Antarctic Ridge. These
areas include the Central American/Mexican subduction
zone, the portion of the San Andreas running from about
116W to 119W in So. California,"

This board has discussed these possibilities in several posts
since that time.

California earthquake listings
(There have been several aftershocks)

http://www.scecdc.scec.org/recenteqs/Quakes/quakes0.html

• California earthquake listings