STRONG (Ms 6.3) EVENT IN NEW BRITAIN MAY HAVE BEEN TRIGGERED

SUMMARY

An earthquake of Ms 6.3 occurred in New Britain this morning less than
two hours after the largest solar flare in more than a week occurred
while New Britain was near sub-solar. In yesterday's report it had been
stated:

"An M2.2+ solar flare occurred this evening at about 00:00 UT
(Feb. 28). This is the largest flare in nearly a week and could
trigger pent-up seismic activity tonight or tomorrow. ...
Such periods of extreme seismic quiet when interrupted by moderate or
strong flare often end with a Mb 6+ earthquake within hours of the flare."

and

"The event at midnight was the largest flare in nearly a week
and could trigger some activity either in the longitudes within
about 30 degrees of 10E or within 30 degrees of 180E within the
next day."

The New Britain event fell at 151E, barely within the stated
30 degrees longitude of 180E so triggering is considered possible
in this case. It was followed by a Mb 5.3 aftershock. These event were
followed by a Mb 4.8 at 178W in the Aleutians and a second Mb 4.8 in the
eastern Aleutians at 163W later in the day, both are within 30 degrees
longitude of 180E. The other Mb 4.8 of the day occurred near Istanbul,
Turkey, again within 30 degrees of the stated 10E subsolar region.
Some influence from the M2.2 flare is considered possible in
each of these instances. After 3 days in which only 3 events in the
world had reached low Mb 5 levels, today, the seismicity of the
earth appeared to rebound. Seven earthquakes were located today
by NEIS with Mb>=4.8, equal to the number seen in the previous 4
days total.

GLOBAL

After 3 days in which only 3 events in the world had reached low
Mb 5 levels, today, the seismicity of the earth appeared to rebound.
Seven earthquakes were located today by NEIS with Mb>=4.8, equal to the
number seen in the previous 4 days total.
The largest events of the day, with the exception of a Mb 5.0
in the region of southern Sumatera all occurred within 30 degrees
longitude of 0E and 180E, possibly suggesting a triggering effect
from the M2.2 solar flare at 00:12 UT this morning and the subsequent
minor geomagnetic storm.
Other events were located in Guatemala (Mb 4.4); Hindu Kush (Mb 4.2, 4.3);
Chile (Mb 4.3) and the Owen Fracture zone in the northern Indian
Ocean (Mb 4.5).

U.S./CANADA

After a slow day on Feb. 27, several hours of the solar flare a
Ml 3.1 event shock the Calexico aftershock zone, followed by a second
Ml 3.0 about 7 hours later. The aftershock zone continued at a moderate
level of seismicity with two more events in the Ml 3 range late
on Feb 28 (Ml 3.2) and following the M1.0 flare at 00:12 on Mar. 1
(the Ml 3.0 occurred at 00:18 UT).
The most unusual event in the U.S./Canada today was recorded
north of Seeley Lake, MT, in Canada with Ml 3.0. This area has
been unusually active for the past several days with a number of
events in the Ml 1.5-2.5 range extending south into Montana.
Earthquakes along the Pacific coast included events in California
at Parkfield (Ml 1.9); Wheeler Ridge north of Los Angeles (Ml 2.0);
Hawthorne Nevada (Ml 2.0, 2.0); Milpitas (Md 2.0); Ferndale off the
Coast of Northern California (Md 2.2) and a minor swarm in the
Geysers region including events of Ml 2.1, 2.1, 2.2, 2.2, and 2.3.
Ten events of Ml>=2 have been recorded in California excluding
Baja aftershocks today. There have been 27 aftershocks of Ml>=2
listed in that sequence on this date.
The largest earthquakes in the U.S./Canada today both occurred
in the Aleutian Island of western Alaska. These were a Mb 4.8
in the Andreanoff Islands and a Mb 4.8 in the Unimak Isl. region
of eastern Aleutians.
No earthquakes of Ml>=3 have been recorded in Hawaii in the past
two weeks.
Two very small tremors were recorded in southeastern Quebec
in the past 24 hours.

NEW ZEALAND

One red-line event near Cannon Point occurred as identified
on the IGNS on-line seismometer today, but parameters have
not yet been supplied by IGNS for this event. The seismometer
continued to be quite noisy again today.

The IGNS on-line Seismometer can be found at:
http://www.gns.cri.nz/news/earthquakes/latest_drum.html

GEOMAGNETIC/SOLAR FIELDS

Two M-Class solar flares occurred since last report, with maximum
intensity occurring exactly 24 hours apart. Each maximized at 00:12 UT
on Feb. 28 and March 1, 2002. The parameters of each are listed
below. Each of these flares was accompanied by a geomagnetic disturbance.
In the first case, the light geomagnetic storm occurred about 09:00 UT
in the later, the storm maximized about 22:30 UT. Neither of these
storms was long or energetic enough to be expected to have a major
effect on global seismicity. The second, however might affect the
regions about the Greenwich and International Date Line meridians,
as did the two solar flares today. This could increase the potential
for another unusual event in these areas.

Flare # START MAX END CLASS

8840 2356 0012 0048 M2.2 (February 28)
0005 0012 0035 M1.0 (March 1)

For general space weather conditions see:
http://sec.noaa.gov/today.html
For Solar flare data see:
http://sec.noaa.gov/ftpdir/indices/events/20020228events.txt
http://sec.noaa.gov/ftpdir/indices/events/20020301events.txt

TOMORROW IN SEISMIC HISTORY

U.S./CANADA

Four large earthquakes have hit the U.S./Canada on Feb. 28, local time.
Yesterday we discussed the Yakutat, Alaska earthquake of Feb. 28, 1979
and the Nisqually earthquake in Washington on Feb. 28, 2001. While events
of Mw 6.7 and 7.0 occurred on Feb. 28, local time in the Yukon in 1955
and in Quebec in 1925, the subject for today is the St. Lawrence earthquake
of Feb. 28, 1925, which actually occurred on March 1 (UT) in the St. Lawrence
Valley Quebec, Canada. A good paper (which might not be currently available
in many libraries) is :

Hodgson, Ernest A., 1927, The St. Lawrence Earthquake, February 28, 1925,
printed by the Royal Society of Canada, Ottawa, 1927.

A brief description of the Yukon Territory event of 1955 follows the
St. Lawrence description.

The earthquake at Mw 7.0 was the strongest to occur in the U.S. or
Canada on March 1 (U.T). It occurred at 02:19 on March 1st (21:19 EST on
Feb. 28). It was felt strongly over eastern Canada and the New England
states. Tremors were felt as far south as Virginia and as far west as
the Mississippi River. Damage was confined to a narrow belt, approximately
twenty miles long, covering both sides of the St. Lawrence, somewhat less
than a hundred miles below the city of Quebec.
The causes advanced for this earthquake are a major, underlying
one, due to an accumulation of stress caused by slow rising of the
Atlantic coast and several "trigger" causes. [This is a quote from
Hodgson's paper, published in 1927; demonstrating that theories about
earthquake triggers are hardly new]

"Among the latter may be mentioned the Sayles theory of the effect
of long periods of drought on a rising section of the coast, and the
estuary tide effect, virtually warping up the outer (east) side of the
fault, due to a high tide, well inside the fault-line zone and a low
tide outside that zone, the conditions obtaining at the time of the
earthquake."

Ice was cracked throughout the region by the passing earthquake
waves. One ice lake was said to have "exploded" at the time
of the quake.

This may be one of the first cases where modern technology was used
to warn a local population of an earthquake BEFORE it was felt (however
inadvertantly). Hodgson notes:

"At Riviere du Loup, the manager of the local telephone
company was listening to WGY broadcasting a dinner concert from
Albany from Albany. His house was, according to his description
careening like a ship at sea, while the musicians played,
still undisturbed" [the concert was disturbed about a minute later].

There were also reports of people on long-distance telephone
conversations when the earthquake occurred who were able to warn
the other party of the coming earthquake.

This was one of the largest earthquakes ever experienced in the
St. Lawrence Valley.

FUTURE HAZARD:

The following earthquakes centered in eastern Canada were comparable
to the 1925 event: Feb 5, 1663; Sep 5, 1732; Dec. 6, 1791; Oct. 17, 1860;
Oct. 20, 1870 and Mar. 1, 1925. These are roughly 60-70 years apart
with the longest inter-event interval 70-80 years. Since it has now
been 77 years since the last such event, it would seees another
earthquake comparable to the 1925 event may be very near or imminent
in this area.

Incidentally, while 1925 was a low solar activity year, there was
a moderate geomagnetic storm which peaked several hours prior
to this earthquake.

YUKON AND WESTERN EVENTS

Several other events in the U.S/Canada on March 1 of Mw>=6 occurred
in the western portions. These included a Ms 6.0 off of Vancouver
Island in 1929 which was felt but did not inflict any damage.
An Mw 6.7 in the Yukon late on Feb. 28 (March 1 UT), was felt
throughout the Yukon and Northwest Territories. Light fixtures
wer seen swaying as far away as Northway, Alaska. This was one
of the largest events recorded in the Yukon Territory.

CALIFORNIA/WESTERN U.S.

No events of Ms>=6 have been recorded in the Western U.S. on
March 1. The most damaging of the Mb>=5 events occurred
in the Fort Tejon area in 1963 (Feb 28, local time). This
event was felt over approximately 8,000 square miles of southern
California where the maximum damage was near Taft where
plaster cracked and cans and ceral boxes fell from shelves
in grocery stores. The shock was felt for 40 seconds at Fort
Tejon State Historical Monument.

WORLD

March 1 has been a relatively quiet day in global seismicity.
Three events of Mw>=7 have occurred on this day including two
in the region between West Irian (Mw 7.0, 1959) and Ceram (Mw 7.9, 1948).
The third was a Mw 7.0 in Peru in 1958. All of these events were
felt but did little damage because of their deep hypocenters.