UNUSUAL LARGE (MW 5.9), DEEP EARTHQUAKE STRIKES AREA SOUTH OF FIJI ISLANDS

SUMMARY

The largest earthquake during the past 24 hours was a Mw 5.9
in the region south of the Fiji Islands. This is an unusual event.
Nearly all events in this region are deep earthquakes (500-700 km depth)
and today's was no exception having a calculated depth of 606 km.
The Pacific plate is diving deeply beneath the Australasian plate
in this area. Since 1960 there have been 8 earthquakes of Mw>=5.9
recorded within 150 km of today's epicenter (about one every 5 years).
However, most of these have occurred since 1990. There were events
of Mw 6.7 (1961) and Mw 5.9 (1966), but then quiescence through
May, 1990 when a Mw 5.8 occurred. In the past 10 years, there have
been 5 earthquakes of Mw>=5.9 in the region (1991 - Mw 6.1;
1994 - Mw 6.7; 1997 - Mw 6.8; 1999 - Mw 6.2 and June 14, 2000 - Mw 6.4).

GLOBAL

Other earthquakes of Mb>=5 during the past 24 hours occurred in
the Northern Molucca Sea, south of the Philippines (Mb 5.0). Earthquakes
of Ml 4.8 (Tonga Islands); ML 4.2 (South of Honshu); and Mb 4.5 and 4.8
(Argentina) were also recorded by teleseismic networks today.

U.S./CANADA

A Ml 2.8 earthquake occurred last night in the east Los Angeles
area of San Marino, CA. This is the largest earthquake within
20 km of this epicenter since June 29, 1999 when a Ml 3.8 occurred
to the southwest. This is one of a series of earthquakes occurring the
region in the past month.
Two earthquakes of slightly less magnitude have occurred within 30 km
in the past year - on Jan 9, 2001 (Ml 2.7) and on April 22, 2001 (Ml 2.6).
Two other earthquakes of Ml 2.8 have also occurred within 30 km since
Jan 1, 2000 (on Mar 7, 2000 and Aug. 1, 2000).
Several additional microearthquakes continued the recent activity
in the L.A. area. outside of the San Marino event. These occurred at
Malibu and Panorama City (Ml 1.8, 1.8).
A minor swarm, probably triggered by the recent geomagnetic activity,
occurred near Gilroy in Central California. The largest event in recent
times occurred near there as the Morgan Hill earthquake of 24 April, 1984
and was also associated with strong X-flares. The Coyote Lake earthquake
(Ml 5.9) in that region on 6 August, 1979 occurred during a strong
geomagnetic storm.
The minor swarm near Calexico which occurred yesterday continued
today with a Ml 2.7 in that region this afternoon.
Two earthquakes also occurred in the Ontario/Quebec region of Canada.
One of these - an Ml 3.1 NW of North Bay, ONT was the largest event
in the U.S./Canada area outside Alaska today. The second occurred
on the Ontario/New York border (Ml 1.8). Another microearthquake
(Ml 1.7) was also reported from the New Madrid, MO area. This area
was under seismic watch from recent geomagnetic storms.
A second earthquake (Ml 3.8) occurred in the Bristol Bay area of
Alaska today following the Ml 4.1 yesterday (see yesterday's report
for details). This was the largest event recorded in the U.S./Canada
region today.
No quakes of ML>2.5 were reported from the Rocky mountain area
or from the Pacific Northwest or Hawaii today.

NEW ZEALAND

The Fiji Island quake lies just north of the New Zealand boundary.
The on-line seismometer showed a number of minor and light earthquakes
in the region today, but no reports were received from IGNS.

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 returned to quiet conditions today. There
were no X- of M-class flares observed on the sun. Seismic watches
remain in effect in areas previously identified through 29 September.

For general space weather conditions see:
http://sec.noaa.gov/today.html
For Solar flare data see:
http://sec.noaa.gov/ftpdir/indices/events/20010927events.txt

TROPICAL STORMS

Hurricane Humberto is moving into the north central Atlantic Ocean
and is expected in the Azores tomorrow. Some seismicity in the
Azores may accompany landfall within two days. A strong earthquake
(Mb 5.3) occurred in that area yesterday so aftershocks are a
real possibility. Humberto is not expected to impact North American
seismicity. For tracking details see:

http://www.wunderground.com/auto/HurricaneSite/tropical/tracking/at200110.html

Hurricane Juliette is weakening off the coast of Baja California
and is expected to become a tropical storm within the next 3 days.
Some minor seismicity may be associated in the Gulf of California.
Four earthquakes (Ml 4.4, 4.3, 4.0, 3.7) today in Guerrero/Oaxaca area
of Mexico were probably promoted by this storm. Seismicity in the
U.S. is not likely to be affected by this storm at this time.
For tracking details see:

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