EARTHQUAKE OF MB>5.2 HITS BAJA CALIFORNIA REGION SOUTH OF YUMA, ARIZONA

SUMMARY

A moderate earthquake of Mb 5.2+ hit the region of Baja California
south of Yuma Arizona this afternoon. This is the first event of
Mb>=5 in the region bounded by 32-30N 116-114W since a Mb 5.3 on
Dec. 3, 1991. It is the third largest event in the region in the
past 35 years - the others being a Mb 5.4 on Aug 31, 1988;
Mb 5.7 on July 17, 1975; and Ms 6.2 on Nov. 23, 1963. SCSN is giving
the following preliminary parameters to this event (which is listed
as much larger at teleseismic observatories, as noted by the
magnitude from NORSAR (NOR)):

O: 08DEC2001 23:36:08 31.9N 115.0W ML=5.2 SCSN SSW of Yuma, AZ
O: 08DEC2001 23:36:07 30.0N 114.4W Mb=5.5 NOR GULF OF CALIFORNIA
UP:10DEC2001 AABA 30.3N 115.5W 10P (12-01-01) (Ml 2.5-4.5 G+)

The area had been expected in these daily reports to see strong activity
around this time from a number of effects which tend to enhance seismicity
levels. These effects included:
NEAR FIELD TRIGGERING

An Mb 4.8 earthquake had occurred several days ago south of this
epicenter in the Gulf of California. Canie had noted on December 3

"We're still in the window from that Mexico-gulf quake set - its about
7-10 days. So thru 12/8 the warning is still on from the other quakes."

See:
http://www.earthwaves.org/wwwboard/messages/11499.html

DONS'S FORECAST:

Don had also anticipated an earthquake in this area, but was
several days early in his forecast:

He had stated:

"Estacion Coahuila, Baha, California Earthquake Forecast
Posted by Don In Hollister on November 13, 2001 at 14:09:54:

Magnitude: 3.0-4.0+
From: 11/19/2001UTC - To: 11/23/2001UTC
Location: Baha, Caliornia
Lat: 32.1N - Long: 114.9W - Range: 40Km

Hi All. The quakes in the area of Bombay prompted me to do a search for an
area that might be ready for something a little larger.

The only one I could find that has a good chance of occurring is at
32.1N/114.9W. This is about 20Km SSE of Estacion Coahuila, Baha, California.

The magnitude on this should be 3.0 to 4.0, but in the event of a geomagnetic
storm 2 to 4 days before the forecasted date the magnitude could be a little
larger."

The current epicenter looks like it may be a mighty good match
with Don's forecast.
See:
http://www.earthwaves.org/wwwboard/messages/10909.html

Seems to me, that when Don posted this forecast, I wrote him saying something
like "It'll never happen ..." I eat my words now. Sorry for doubting, Don.

FAR-FIELD EFFECTS:

1) Far-Field Triggering from the great Kunlun Mts. earthquake of
Nov. 14, 2001 (Mw 8.1)

The event lies directly on the boundary of the S-wave shadow zone
(107 degrees) from the great Kunlun Mts. earthquake. The far-field
forecast from that event had stated:

"103-107 degrees***: California/Baja border (about 32-34N)

***: The strongest triggering is always expected to be along the
shadow zone boundary between 103-107 degrees from the epicenter."

and

"Areas of U.S. and Canada where triggering may occur (Ml>=4.0)

...Southern California - esp. in the Calexico to Bombay Beach region"

FAR-Field from HAAST, N.Z. quake yesterday:

This epicenter is also at 103 degrees from the Ms 6.2 earthquake
on South Island, New Zealand yesterday - at the p-wave shadow zone
boundary. That earthquake was the strongest in that region in more
than 35 years.
DELAYED EFFECTS FROM NEW BRITAIN EVENT MW 7.1 OCT. 31, 2001

On Nov 26, this forecast had reminded us of the relation between
moderate or strong events in Southern California and earlier events
in southern California:

'Seismicity often increases in So. California about a month following
strong earthquakes in the New Britain region. The far-field aftershock
forecast of the Mw 7.0 New Britain event on October 31 had noted:

" There is a strong relationship between New Britain events and
succeeding earthquake in southern California especially in the
area of Anza to the Salton Sea. This is probably because wave
fronts from New Britain arrive approximately parallel to the
San Andreas in this region, promoting larger events. This area
should remain active for several week. A larger event in this
area often occurs 28-33 or 43-46 days after the event in New
Britain, so the danger is not yet over."

The danger period should begin on November 28 and last through
Dec. 3, 2001.'

Today's event between the two stated danger periods, but could well
have been related to the same triggering effects.