GLOBAL SEISMICITY AT LOW LEVELS, NO SIGNIFICANT EARTHQUAKES TODAY

SUMMARY

No earthquakes of Mb>=5.3 occurred in the world today. No damaging
or destructive earthquakes were noted. The largest earthquake of the
day occurred in southern Alaska (Mb 5.2) and in Banda Sea (Mb 5.2).
Only three earthquakes of Mb>=4.5 have been listed for Feb. 25, 2002.

GLOBAL

The strongest earthquakes recorded in the world today were Mb 5.2
in southern Alaska and the Banda Sea region. Moderate to light earthquakes
were also recorded off the east Coast of Honshu (Mb 4.6); in the
northern Mariana Islands (Mb 4.6) and in Kyrgyzstan (Ms 3.1). A swarm
of light earthquakes was also noted in the Aegean Sea and in NW Turkey
(maximum magnitude Ml 3.7).

U.S./CANADA

The strongest earthquake recorded in the region of the U.S./Canada
was a Ml 5.2 in southern Alaska near the epicenter of the great
Good Friday quake of March 28, 1964. Alaska is often active during
late February (see History section below). The earthquake was
felt sharply at Tatiliak this afternoon, and was the largest to occur
in the U.S./Canada on Feb. 25 since 1990 when a Mb 6.0 hit SE Alaska.
No damage has been reported with today's Alaska earthquake. For a complete
report see:

http://www.aeic.alaska.edu/Seis//Input/mitch/frame2html/frame2html/results//20020225211925_.pdf

Several regions of California and Nevada have shown moderate activity over
the past 24 hours including Mammoth Lakes, where a minor swarm struck
last night with maximum Ml 2.6; Calexico which has seen three aftershocks
of Ml 3.0; the Obsidian Butte region north of the aftershock zone where
six earthquakes of Ml>=2 have occurred today and the Telescope Peak area
on the southern California/Nevada border which experienced a Ml 3.2
and several aftershocks. Solitary events of Ml>=2 occurred near
Eureka in Northern California (Ml 2.3); Yorba Linda, SE of Los Angeles
(Ml 2.2); and near Ukiah in northern California (Ml 1.9, 2.2).

The southeastern portion of Canada also show moderately strong
regional seismicity over the weekend. In addition to the Ml 3.0
on the Quebec/N.Y. border reported on yesterday, a Ml 2.9 occurred
in Central Quebec near Ungava on Saturday and there were two earthquakes
in SE Quebec (Ml 1.4, 1.5).

In Western Canada Vancouver Island region saw events of Ml 3.3 and
2.9 today and on Saturday 23 Feb. A Ml 2.7 occurred in western Vancouver
on Sunday, Feb. 24.

Four areas of the Pacific Northwest also saw seismic activity today -
events of Ml 1.6 and 1.7 near Canby, Oregon; Ml 2.2 near Yakima, WA, 1.4
near Sedro Wooley, WA and finally a Ml 1.2 near Forks, WA. Several events
of Ml>=2 have also occurred in the Rocky Mountain region in the past
several days.

NEW ZEALAND

The IGNS on-line seismometer today was quite noisy, but IGNS did
not issue information on any earthquakes that occurred today.

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

GEOMAGNETIC/SOLAR FIELDS

The geomagnetic field remained at quiet conditions today. The largest
solar flare was a M1.0 this morning (UT). Two earthquakes associated
with this flare were Ml 1.9 in the Calipatria region of So. California and
a Ml 1.7 near Obsidian Butte. These areas have shown a strong increase in
seismicity since the Baja quake of 2-22-02. Today's events occurred at
02:47 and 02:53 UT respectively as the flare was beginning and
approaching maxima. Parameters for this flare follow:

Flare # START MAX END CLASS

7860+ 0247 0257 0300 M1.0

For general space weather conditions see:
http://sec.noaa.gov/today.html
For Solar flare data see:
http://sec.noaa.gov/ftpdir/indices/events/20020225events.txt

TOMORROW IN EARTHQUAKE HISTORY

WORLD

February 26 has been a relatively light day in earthquake history.
The only event to have occurred on this day with recorded damage and
death associated was in 1961. This event was an Ms 7.2 in the Kyushu
region of Japan. Two deaths were associated with the quake and 7 were
injured. 170 homes were destroyed at Miyazaki. A three-foot tsunami
was observed in southwest Shikoku Island, Japan.
Six events of Ms>=7 have been recorded on February 26. They occurred
in 1909 (Ms 7.1, Galapagos area); 1914 (Ms 7.2, Peru/Bolivia); 1945
(Ms 7.1, Bonin Islands); 1952 (Ms 7.0, Peru/Bolivia); 1953 (Ms 7.0,
Kamchatka) and 1953 (Ms 7.0, Solomon Islands) and in 1961 (Ms 7.1, Kyushu).
The two events in 1953 may be an example of far-field triggering as
the second earthquake of Ms 7.1 in the Solomon Islands lies approximately
61 degrees from the first in Kamchatka, a distance at which seismic
energy is concentrated after large events. The 1953 Kamchatka earthquake
was followed within four hours by a swarm in the Bakersfield, CA region,
California including a Ml 3.5 and 3.7 event which broke windows locally
and at the same time a swarm in the Wellington, New Zealand area
including magnitudes 3.7 and 3.8.

No events of Ms>=7 have occurred on Feb. 26 in the past 40 years.

U.S./CANADA

Coincidentally, the largest earthquake that has been recorded in
Alaska or Canada on 25 or 26 February occurred three hours before
the Kamchatka event on 25 February, 1953 (another example of
far-field triggering?). The Alaskan earthquake apparently occurred
as a Ms 6.8 on the Alaska Peninsula and is listed in catalogs from
the Decade of North American Geology, International Seismological
Service and UNESCO. Curiously, however no reference to this earthquake
is made in the U.S. Earthquakes report for 1953 nor in the U.S.
History although it has been listed in the revised Seismicity of
the U.S. (USGS Professional Paper, 1527). It seems an earthquake
of this size would have been noted in the U.S. Earthquakes in 1953,
so here is a conundrum for historians - did this earthquake occur,
and if so, why was there no note of it taken at the time in U.S.
earthquake publications?
In recent years the Alaska Peninsula area has also been active
on Feb. 26 with earthquakes of MB 5.4 in 1987 and Mb 5.0 in 2000.
The largest events on Feb 25 in California both occurred
in the region near the current swarm of aftershocks and triggered
earthquakes in Baja and northward to Ocotillo. These were a Ml 5.1
south of Yuma AZ in 1956 and a Ml 5.6 south of Palm Desert, CA
in 1980, which caused slight damage. A similar event occurred as a
Ml 5.0 in Baja in 1930 on Feb. 26.
February 26, however, has seen more activity in the Central California
area including events of M 5.9 in 1864 and 5.0 in 1932. The event in
1864 cracked adobe walls at Monterey and caused objects to fall over at
Watsonville, it was severe at San Francisco and Santa Cruz. The 1932
event occurred near Big Sur, CA.

No events of MB>=6 have occurred in the U.S./Canada region on
Feb. 26 in the past 49 years.