U.S. EXPERIENCES STRONG FAR-FIELD QUAKE SEQUENCE FROM PACIFIC-ANTARCTIC RIDGE

The far-field aftershock forecast from the Ms 6.5 in the Pacific-
Antarctic Ridge earthquake (PAR) on 2 September had noted that a broad
band between approximately 34-36 degrees north in the U.S. ought
to experience a strong enhancement in seismicity following that
event. This observation was based on past historical seismicity
following earthquake in that area of the PAR.

Since that event a series of remarkable earthquakes have occurred
in the region between 33-37 degrees north in the U.S.

The first of these occurred about 4 hours after the PAR event
in Southern South Carolina or Northern Georgia. This Ml 2.7 earthquake
was the largest within 100 km of it's epicenter in about 5 years.
The far-field forecast had specifically mentioned northern Georgia
as an area where far-field triggering was likely. This event
was located at approximately 34 degrees N latitude.

The second earthquake (another Ml 2.7) occurred in the Wichita
Mountains region of Oklahoma. This was the largest earthquake in
Oklahoma since April, 2000 and January 2000 when events of Ml 2.8 and
2.9 occurred. This event was located at approximately 35 degrees
north latitude.

The third earthquake (Ml 2.0) occurred in the New Madrid region
and had been preceded by two other earthquakes in that area earlier
on the 2nd. It has been noted before that before large global events, it
is common to see small earthquakes pop up in the New Madrid area.
This earthquake was located at approximately 36 degrees North latitude.

The next earthquakes occurred in the Southern California area
(Ml 2.9) west of Los Angeles. This sequence is still continuing. This
was the largest event within 40 km of this epicenter since May, 2001.

The final earthquakes occurred this morning (Ml 4.0, 3.4) in the
region west of Trinidad, Colorado. These were the largest earthquakes
in this area since 1973. Only two other events of this size or larger
have ever been recored in SE Colorado (37-39N 106-102W).

The forecast had stated regarding this activity:

"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)

Washington/Oregon border area
Southern California 115-119.5W 32-35N
A section between 34-36N from Virginia, New Madrid, Arizona,
Southern California"
and

"New Madrid has been activated on two occasions
(36N 89W, Ml 3.0, 3.5)."

and

"101-105 degrees***: No. Georgia"

The following are the parameters for these events and data sources:

Oklahoma:

O: 2SEP2001 22:48:42 35.0N 98.9W ML=2.7 OKGS Wichita Mts KIOWA CO, Oklahoma

Source:

http://www.okgeosurvey1.gov/level2/okeqcat.index.html

Central U.S. (Colorado, New Madrid, No. Georgia/So. Carolina)

O: 04SEP2001 12:45:53 37.1N 104.6W ML=4.0 CERI WEST OF TRINIDAD, CO
O: 04SEP2001 12:22:45 37.1N 104.6W ML=3.4 CERI WEST OF TRINIDAD, CO
O: 04SEP2001 5:19:22 36.4N 89.5W ML=2.0 CERI N of Tiptonville TN
O: 02Sep2001 13:56:09 33.8N 82.4W LG=2.7 NEIS NORTHERN GEORGIA, USA
O: 02SEP2001 13:56:09 33.8N 82.3W ML=2.7 CERI S of Greenville SC
O: 2SEP2001 0:46:53 36.1N 89.0W ML=2.4 CERI E of Newbern TN
O: 2SEP2001 0:37:07 36.1N 89.6W ML=1.8 CERI S of Caruthersville MO

Sources:

http://folkworm.ceri.memphis.edu/recenteqs/Quakes/quakes0.html
http://wwwneic.cr.usgs.gov/neis/bulletin/bulletin.html

Southern California (L.A. to Santa Barbara)

O: 04SEP2001 17:48:52 34.4N 118.6W ML=1.5 SCSN WSW of Valencia, CA
O: 04SEP2001 16:49:50 34.4N 118.0W ML=1.7 SCSN N of Mt. Wilson Observatory, CA
O: 04SEP2001 14:52:57 34.1N 118.5W ML=1.9 SCSN WNW of Westwood Village, CA
O: 04SEP2001 14:48:01 34.4N 118.6W ML=1.7 SCSN WSW of Valencia, CA
O: 03SEP2001 18:15:39 34.3N 118.7W ML=1.5 SCSN NNW of Simi Valley, CA
O: 03SEP2001 18:13:49 34.4N 118.6W ML=2.9 SCSN SW of Valencia, CA
O: 03SEP2001 13:19:49 33.3N 119.2W ML=2.8 SCSN SW of Santa Barbara Is. , CA

http://quake.usgs.gov/recenteqs/Quakes/quakes0.html

Moderate earthquakes have also occurred in Honshu (Mj 5.4), Tonga/Fiji
(Ms>5); and Oaxaca, Mexico also areas where strong far-field aftershock
were also expected. But that is a story for another day.