Part of what I do here is to prepare an earthquake summary for each day for use by
various groups. Since I do this anyway, I thought it might be useful to post
these each day so that the readers of this board could keep abreast of current
events on a daily basis. So here is the first. If you have additional information
or things you would like included in this summary, please let me know.

EARTHQUAKE MB 5.2 HITS SOUTHERN GREECE, MW 6.0 STRIKES TONGA ISLANDS

SUMMARY

An earthquake of Mw 6.0 occurred in the Central Tonga Islands
this morning. This is the second event of Mb>=6 in the region
within 200 km of today's epicenter this summer (the other being
on July 4, 2001 (Ms 6.5). These were the first events of Mw>=6
in the region since April 1999. There have been 107 earthquakes
recorded of Mw>=6 in this region since 1907.
The preliminary (NEIS) parameters of this event were:
O: 15SEP2001 15:04:37 22.3S 175.0W MB=6.0 NEIS TONGA ISLANDS REGION

Early on the morning of 16 September a moderate earthquake was
also recorded in the region of southern Greece. The first reports
on this event give an Mb of 5.2 however, seismograms suggest that
Ms may be larger. This epicenter is located directly west of
Athens. Some local damage is likely. This is the largest earthquake
in our data base within 100 km of this epicenter since a similar
Mb 5.2 occurred on June 11, 1999. The last earthquake in this
area which was larger was a Mw 6.5 on October 13, 1997.

The preliminary (NEIS) parameters of this event were:
O: 16SEP2001 02:00:51 37.3N 22.1E Mb=5.2 NEIA SOUTHERN GREECE

GLOBAL

In addition to the Tonga and Greece earthquakes, events were
observed in the swarm near Vancouver Island (Mb 4.9 4.8 3.9) and
in Northern Chile (Ml 4.9). An event of Ml 3.7 had been reported
in the Ionian Sea yesterday (Sept. 14)

U.S./CANADA

It has now been 5 days since the last event of Ml>=3 in the
lower 48 states of the U.S. This is quite a long period between
events of this size in the contiguous U.S. In fact, the longest
quiescent period in the past two days has been 5 days (ending
on Feb 19, Nov 30 and OCt 8, 2000). So, we should expect an earthquake
of Ml>=3 in the U.S. within a day.
The largest earthquake in the California/Nevada area today was
a Ml 2.6 in the Geysers area. A Ml 2.6 also occurred near Hemet,
southern California last night.
But the largest event in the contiguous U.S. over the past two
days was a Ml 2.9 near Mt. Hood, Oregon where a swarm began on
Sept 12 and is continuing till this time.
Alaska showed no significant activity (no events of Ml>=3 today).
In Hawaii, the Lo'ihi Seamount sequence appears to be temporarily
over. There were no events located in that area today. However two
events of Ml 3.1 did occur inland, so a migration towards the
big Island may be occurring.
The largest earthquakes of the day in the U.S./Canada region, however,
continued to be the swarm south of Vancouver Island, B.C. Earthquakes
of Ml 4.9 and Ml 4.8 occurred in that area today along with a smaller
Ml 3.9.
GEOMAGNETIC/SOLAR FIELDS

Minor geomagnetic storm commenced at approximately 21 UT on
14 September and at 12 UT on 15 September since the last report.
Neither of these storms lasted more than 6 hours and neither exceeded
Kp>4. Thus no seismic watches were issued as a result of these
storms. Two minor M-class solar flares occurred today. Their
parameters were:

Flare # START MAX END CLASS

4040 + 1104 1128 1154 M1.5
4120 + 1544 1559 1610 M1.3

For general space weather conditions see:
http://sec.noaa.gov/today.html
For Solar flare data see:
http://sec.noaa.gov/ftpdir/indices/events/20010915events.txt

Earthquakes of Ml 1.2 (Anza, CA 11:07 UT), Ml 1.9 (Tokop NV, 11:19 UT)
and Ml 0.8 (Idyllwild, CA) occurred during the first of these flares.
No earthquakes have yet been reported during the second flare.

TROPICAL STORMS

Tropical Storm Gabrielle passed over Central Florida today doing
moderate damage from Sarasota/Tampa area to Orlando and Cape Canaveral.
Four inches of rain fell in Sarasota. The storm was accompanied by
several tornados. Tampa Bay got up to 3 inches per hour this afternoon.
Since Sarasota was my winter home this year, reports of this storm
are of special interest to me. Gabrielle is now headed out into the
Atlantic. As reported yesterday, the most likely seismicity associated
with this landfall would be along the Mexican subduction zone as the
storm would tend to push North America to the NE relieving some normal
stress and hence friction in this subduction zone. This would allow
larger than normal earthquakes to occur. There was a Mb 5.1 in
Michoacan, Mexico as the storm hit Florida followed by a Ml 4.6
in the Gulf of Tehuantepec this afternoon. The magnitudes of these
events may have been increased due to the effects of Gabrielle.

For information on Gabrielle see:
http://www.wunderground.com/auto/HurricaneSite/tropical/tracking/at200108.html

The only other hurricane of tropical storm affecting areas near
the U.S. at this time is Hurricane Felix which continues on its
course towards the Azores Islands. Tracking information suggests
a strike in the Azores tomorrow (September 16). Some associated seismicity
may be observed along the north mid-Atlantic ridge and in the
Azores in the next 3-4 days.

For information on Hurricane Felix see:
http://www.wunderground.com/auto/HurricaneSite/tropical/tracking/at200108.html
and
http://abcnews.go.com/wire/US/ap20010915_1110.html