STRONG GEOMAGNETIC STORM TODAY COULD TRIGGER STRONGER SEISMICITY

SUMMARY

A strong geomagnetic storm began about 06:00 UT today and lasted
through 20:00 UT. Strong and long-lasting geomagnetic storms are
often followed at high latitudes and in sub- and anti- solar
longitudes by an increase in seismicity from one to four days
following the storm commencement.

GLOBAL

The stronger global events of the past two days have occurred
in Europe. Unusual earthquakes of Ml 4.8 (Poland), Mb 4.6 (Greece)
and Mb 4.9 (Spain) have marked this activity. Only one other earthquake
of Mb>=4 was reported by teleseismic networks today - that was a
Ml 4.2 in the Andaman Islands south of India. A mild earthquake was
also reported by NOR (Mb 4.9) in Tanzania. Seismograms show a small earthquake
in this general vicinity, however NOR consistently has poor locations
and magnitudes, so where and how big this is remains uncertain at this time.

U.S./CANADA

It was another relatively quiet day in the U.S. and Canada. However,
the geomagnetic storm today occurred while much of the region was
anti-solar, and could begin to affect seismicity in the region tonight
or tomorrow. Hurricane Juliette is also a threat to Mexico at this
time and may trigger a moderate earthquake in the Jalisco/Guerrero/
Michoacan/Gulf of California in the same time frame.
The largest earthquake in the California/Nevada today was a Ml 3.0
near Anza. Only two other confirmed earthquakes of Ml >=2 have
occurred in the contiguous U.S. in the past 36 hours - a Ml 2.0
near the Geysers, California and a Ml 2.1 SW of Concord California
this evening.
Of course, with most local networks shut down for the weekend, this
may change tomorrow. However seismometers show little activity
occurring this weekend.
Four earthquakes of Ml>=3 were reported in Alaska in the past 24
hours, however. These were mostly in the Gulf of Alaska area, and
were not locally hazardous.
One event of Ml 3.0 was reported from Hawaii, however will probably
be reduced in size with manual examination.

NEW ZEALAND

IGNS reported an earthquake Ml 3.7 southeast of Westport, So. Island
this morning. No other strong or moderate earthquakes could
be seen on the on-line seismometer for today.

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

GEOMAGNETIC/SOLAR FIELDS

A strong geomagnetic strom began about 06:00 UT today (23 September)
and continued through 20:00 UT. This storm is most likely to affect
areas within 20 degrees longitude of 90 W and 90 E longitudes and
area above 50 N and below 50 S for the next two to three days.
No solar flares of M- or X-class were observed on the sun today.

For general space weather conditions see:
http://sec.noaa.gov/today.html
For Solar flare data see:
http://sec.noaa.gov/ftpdir/indices/events/20010923events.txt

TROPICAL STORMS

Hurricane Humberto is about 500 km east of North Carolina. This
storm is not expected to make landfall on North America. Seismic
triggering from Humberto will probably be minimal.
For tracking information see:
http://www.wunderground.com/auto/HurricaneSite/tropical/tracking/at200110.html

Tropical Storm Juliette has rapidly strengthened to Class 4 Hurricane
status. It is expected to reach class 5 early on Monday. This is the strongest
hurricane wind class. It is currently off the coast of Guerrero/Michoacan
Mexico, where 3 mild earthquakes occurred this afternoon in association with
this storm. For a list of recent earthquakes in Mexico see:
http://www.ssn.unam.mx/~yi/SSN/ssn-ultimos.html
Juliette is expected to move up the coastline of western Mexico and
into the Gulf of California. With it's present wind strength, it
could pose a significant hazard to the Mexican coastline as well as
increasing the potential of a moderate to strong earthquake along
the Jalisco/Michoacan/Gulf of California area in the next 3 to 4 days.
For public advisory see:
http://www.wunderground.com/auto/HurricaneSite/tropical/ep200111.public.html

For tracking Details see:
http://www.wunderground.com/auto/HurricaneSite/tropical/tracking/ep200111.html

Typhoon Lekima is moving north of Luzon, Philippines, south of
Taiwan. Typhoon warnings are posted for Taiwan. Two mild earthquakes
in Taiwan have thus far been associated with this storm. For additional
details see:
http://www.wunderground.com/auto/HurricaneSite/tropical/wp200101.public.html
and
http://www.cwb.gov.tw/V3.0e/content/warning-eng-content.htm