EXTREMELY QUIET CONDITIONS COULD BE ENDING LATER TONIGHT WITH M2.2 FLARE

SUMMARY

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. Seismicity
was extremely quiet throughout the U.S. and the world today. There
were no events of Mb>=4.5 listed by NEIC in the world and no
events of Ml>=3 in the U.S. or Canada today. 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.

GLOBAL

NEIC did not list any events for today. Local networks also did
not locate any significant earthquakes today.

U.S./CANADA

In the past 24 hours, there have been 7 events of Ml>=2 in the
western U.S./Canada (excluding Alaska) region. These have been
concentrated in California in the Tonopah Junction region of
Nevada/California and in the Geysers, California, which appears
to be very sensitive to solar flares today. In Tonopah area the
largest event in a minor swarm was Ml 2.4; likewise in a minor
swarm in the Geysers, the maximum magnitude event was Ml 2.5.
Two aftershocks at the Calexico site had Ml 2.8 and 2.7. Several
other events occurred in the Morongo Valley region in southern
California (Ml 2.4).
Two events of Ml 1-2 were located in the Pacific northwest, however,
earlier this morning two other events with probable magnitude
2-3.5 were recorded off the coast of Northern California and
Oregon.
No events were listed for the Rocky mountain region or the Eastern
U.S. or Canada today. A swarm of minor events occurred near
Haines, Alaska today (Ml 3.5, 2.9, 2.5).

NEW ZEALAND

The on-line seismogram from IGNS continued quiet noisy today,
however, IGNS did not report any new seismic event parameters.

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 throughout the
day. On solar flare of M-Class was observed (M1.6), parameters for
which follow. Moderately strong M2.2 flare also struck this evening
at nearly midnight UT. This flare was accompanied by a minor swarm
in the Geysers, CA region (Ml 1.4, 1.5, 1.6). A Ml 1.6 earthquake
also hit the Geysers at 15:48 UT at the start of the first M1.6 flare.
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.

Flare # START MAX END CLASS

8740 1548 1558 1604 M1.6
2356 0012 0048 M2.2

For general space weather conditions see:
http://sec.noaa.gov/today.html
For Solar flare data see:
http://sec.noaa.gov/ftpdir/indices/events/20022702events.txt

TOMORROW IN EARTHQUAKE HISTORY

U.S./CANADA

February 28 has been an active day in U.S. earthquake history. It
has been exactly one year now since the Nisqually earthquake (Ms 6.8)
hit the Olympic Peninsula near Seattle Washington in 2001. This was
the largest event in the continental U.S. on Feb. 28, although not the
largest in the U.S. on this date.
The Nisqually earthquake is well documented on web pages. An interesting
appraisal of the economic consequences of this event can be found at:

http://seattle.bizjournals.com/seattle/stories/2002/02/25/story1.html

A good page for general information and searching is:

http://maximus.ce.washington.edu/~nisqually/links/links.html

and

http://maximus.ce.washington.edu/~nisqually/

Several sites offer photographic evidence of this earthquake which shock
much of Washington state, but did much less damage than comparable sized
events in other areas of the world. Photos can be found at:

http://seattletimes.nwsource.com/photogallery/quake/

But, as I was saying, the Nisqually earthquake was not the largest
earthquake to strike the U.S. on February 28. That honor goes to the event
in Yakutat, Alaska region on 28 February, 1979. That event was Ms 7.3 and
was felt over an area of about 500,000 sq. miles of Alaska, Yukon and
British Colombia. Seven major earthquakes have been located in this area
of Alaska between 1899 and 1979, three of which were Mw>8. The earthquake
did minor damage throughout the region, but because the area is an ice field,
damage was limited and there were no deaths recorded. A 15-cm tsunami was
recorded at Yakutat, Alaska.

The other earthquake of Mw>6 to occur in the U.S. on Feb. 28 was the
Upland CA, earthquake of 1990. This event (Ms 6.2) injured 30 people and
caused damage estimated to be $12.7 million. It was the second (after
Whittier) of a series of damaging earthquakes in the Los Angeles area from
1987 - 1997.

GLOBAL

Three great earthquakes (Mw>8) have been recorded as having occurred
on February 28. The first of these was a Mw 8.1 in the region of
Central Peru near the epicenter of the great Peru earthquake of last
summer. This event occurred in 1600 and did limited damage in the
Arequipa and Omate regions of southern Peru.
The second great earthquake on this date struck in the Kuril Islands
in 1950. No damage was recorded with this earthquake, probably because
of the 350 km depth of it's hypocenter.
The last great earthquake on this date occurred in the North Atlantic
Ocean off the Coast of Portugal in 1969 (Mw 8.0). This epicenter was
near the epicenter of the great Lisbon earthquake in 1755, one of the
most disastrous earthquakes to strike in western Europe. A second great
earthquake struck the same area in 1975 (Mw 8.1). Neither of the events
in the past 40 years has created a tsunami or caused cultural damage.
The only earthquake on Feb. 28 which is known to have killed anyone
occurred in 1855 in the same area as the great earthquake of
August 17, 1999. The 1855 event killed more than 1600 and had Magnitude
approximately 7.5 causing extensive damage in Turkey and Asia Minor;
Adrianople, Dardanelles and Gallipoli. A similar damaging event had
occurred slightly south four years earlier on Feb. 28, 1851.